@article { ISI:000263071500026, title = {Two modes of O-H center dot center dot center dot O hydrogen bonding utilized in dimorphs of racemic 6-O-acryloyl-2-O-benzoyl-myo-inositol 1,3,5-orthoformate}, journal = {Acta Crystallographica Section C-Crystal Structure Communications}, volume = {65}, year = {2009}, month = {FEB}, pages = {O54-O57}, publisher = {WILEY-BLACKWELL PUBLISHING, INC}, address = {COMMERCE PLACE, 350 MAIN ST, MALDEN 02148, MA USA}, abstract = {

The title compound, C(17)H(16)O(8), yields conformational dimorphs [forms (I) and (II)] at room temperature, separately or concomitantly, depending on the solvent of crystallization. The yield of crystals of form (I) is always much more than that of crystals of form (II). The molecule has one donor -OH group that can make intermolecular O-H center dot center dot center dot O hydrogen bonds with one of the two acceptor C O groups, as well as with the hydroxyl O atom; interestingly, each of the options is utilized separately in the dimorphs. The crystal structure of form (I) contains one molecule in the asymmetric unit and is organized as a planar sheet of centrosymmetric dimers via O H center dot center dot center dot O hydrogen bonds involving the OH group and the carbonyl O atom of the acryloyl group. In the crystal structure of form (II), which contains two independent molecules in the asymmetric unit, two different O-H center dot center dot center dot O hydrogen bonds, viz. hydroxyl-hydroxyl and hydroxyl-carbonyl (benzoyl), connect the molecules in a layered arrangement. Another notable feature is the transformation of form (II) to form (I) via melt crystallization upon heating to 411 K. The higher yield of form (I) during crystallization and the thermal transition of form (II) to form (I) suggest that the association in form (I) is more highly favoured than that in form (II), which is valuable in understanding the priorities of molecular aggregation during nucleation of various polymorphs.

}, issn = {0108-2701}, doi = {10.1107/S0108270109000225}, author = {Krishnaswamy, Shobhana and Gonnade, Rajesh G. and Bhadbhade, Mohan M. and Shashidhar, Mysore S.} } @article { ISI:000284266200038, title = {Helical self-assembly of molecules in pseudopolymorphs of racemic 2,6-di-O-(4-halobenzoyl)-myo-inositol 1,3,5-orthoformates: clues for the construction of molecular assemblies for intermolecular acyl transfer reaction}, journal = {Crystengcomm}, volume = {12}, number = {12}, year = {2010}, month = {Aug}, pages = {4184-4197}, publisher = {ROYAL SOC CHEMISTRY}, address = {THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND}, abstract = {

The crystal structure of racemic 2,6-di-O-benzoyl-myo-inositol 1,3,5-orthoformate (1) which underwent a facile intermolecular benzoyl transfer reaction in the solid state, revealed a helical assembly of molecules along the two-fold screw axis via O-H center dot center dot center dot O hydrogen bond bringing the electrophile (C=O) and the nucleophile (-OH) in close proximity along the helical axis. However, structurally related racemic 2,6-di-O-(p-halobenzoyl)-myo-inositol 1,3,5-orthoformates (bromo (2) and chloro (3)) produced triclinic dimorphs (both P (1) over bar) when crystallized from methanol and ethyl acetate. Molecules in either form did not assemble spirally (like 1), and instead exhibited a one-dimensional isostructurality, bridging O-H center dot center dot center dot O linked identical molecular strings via C-H center dot center dot center dot O interactions across the inversion center. However, the molecules of 2 and 3 assembled in a helical manner similar to 1 with inclusion of solvent molecules in the crystal lattice when crystallized from other common organic solvents. Remarkably, in all the solvates the host molecules formed strikingly similar helices around the crystallographic 2(1)-screw axis through O-H center dot center dot center dot O bond involving the -OH group and carbonyl oxygen of the equatorial C2-O-benzoyl group. Comparison of the crystal structure of dimorphs and the solvatomorphs revealed that the solvent molecules, which interact with the orthoformate-bridge, trigger the helix formation of the host. The difference in the crystal structures of solvatomorphs arises in the interlinking of the neighbouring helices, which creates voids of different sizes to accommodate the solvent molecules. All the solvates crystallized in the monoclinic system distributed over three different space groups P2(1)/n, P2(1)/c and C2/c. In the P2(1)/n system, the adjacent helices are linked via C-X center dot center dot center dot O contacts, in P2(1)/c via C-H center dot center dot center dot X (X Cl, Br) contacts and in C2/c via short X center dot center dot center dot X contacts (X = Cl). The helical organization achieved through solvent mediation and inclusion is of significance in creating molecular packing for intermolecular acyl transfer reactions in crystals.

}, issn = {1466-8033}, doi = {10.1039/b924482d}, author = {Krishnaswamy, Shobhana and Gonnade, Rajesh G. and Shashidhar, Mysore S. and Bhadbhade, Mohan M.} } @article { ISI:000296738500014, title = {Comparison of racemic epi-inosose and (-)-epi-inosose}, journal = {ACTA Crystallographica Section C-Crystal Structure Communications}, volume = {67}, number = {11}, year = {2011}, month = {NOV}, pages = {O435-O438}, publisher = {WILEY-BLACKWELL}, address = {COMMERCE PLACE, 350 MAIN ST, MALDEN 02148, MA USA}, abstract = {

The conversion of myo-inositol to epi-inositol can be achieved by the hydride reduction of an intermediate epi-inosose derived from myo-inositol. (-)-epi-Inosose, (I), crystallized in the monoclinic space group P2(1), with two independent molecules in the asymmetric unit [Hosomi et al. (2000). Acta Cryst. C56, e584-e585]. On the other hand, (2RS,3SR,5SR,6SR)epi-inosose, C6H10O6, (II), crystallized in the orthorhombic space group Pca2(1). Interestingly, the conformation of the molecules in the two structures is nearly the same, the only difference being the orientation of the C-3 and C-4 hydroxy H atoms. As a result, the molecular organization achieved mainly through strong O-H center dot center dot center dot O hydrogen bonding in the racemic and homochiral lattices is similar. The compound also follows Wallach{\textquoteright}s rule, in that the racemic crystals are denser than the optically active form.

}, issn = {0108-2701}, doi = {10.1107/S0108270111039412}, author = {Krishnaswamy, Shobhana and Patil, Madhuri T. and Shashidhar, Mysore S.} } @article { ISI:000289364600022, title = {Intermolecular benzoyl group transfer reactivity in crystals of racemic 2,6-di-O-benzoyl-myo-inositol 1,3,5-orthobenzoate: controlling reactivity by solvate (pseudopolymorph) formation}, journal = {Crystengcomm}, volume = {13}, number = {9}, year = {2011}, month = {MAY}, pages = {3258-3264}, publisher = {ROYAL SOC CHEMISTRY}, address = {THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND}, abstract = {

Racemic 2,6-di-O-benzoyl-myo-inositol 1,3,5-orthobenzoate (rac-3), which usually crystallizes in a monoclinic lattice (Form I, P2(1)/c) from common organic solvents, when crystallized from 2-propanol yielded concomitantly, thin whisker like crystals (Form II, triclinic, P (1) over bar) with inclusion of 2-propanol and water molecules, along with the Form I crystals. Thin fibre-like crystals were also obtained on crystallization from toluene, with inclusion of toluene and water in the crystal lattice (Form III). The Form II and Form III crystals could be converted into the Form I crystals thermally via melt crystallization. Form I crystals exhibit a facile transesterification reaction, but the solvated crystals are unreactive under the same conditions until their transformation to the reactive form. The reactivity patterns of the Form I and Form II crystals correlate well with the molecular organization in them. Since reactivity of the crystals of rac-3 depends on the solvent and the method of crystallization, and the thermal transition of one crystal form to the other, these phase changes can be used as a switch to control the benzoyl transfer reactivity of the constituent molecules in crystals.

}, issn = {1466-8033}, doi = {10.1039/c1ce05054k}, author = {Krishnaswamy, Shobhana and Shashidhar, Mysore S. and Bhadbhade, Mohan M.} } @article { ISI:000292472400016, title = {Protecting group directed stereoselective reduction of an epi-inosose: efficient synthesis of epi-inositol}, journal = {Tetrahedron Letters}, volume = {52}, number = {29}, year = {2011}, month = {JUL}, pages = {3756-3758}, publisher = {PERGAMON-ELSEVIER SCIENCE LTD}, address = {THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND}, abstract = {

A facile and high yielding synthesis of epi-inositol via stereoselective reduction of a pentaprotected epi-inosose is reported. Extent of stereoselectivity during the hydride reduction appears to depend on the ability of the substrate to complex with metal ions in the reducing agent. (C) 2011 Elsevier Ltd. All rights reserved.

}, keywords = {Cyclitol, Inositol, Polyol, reduction, Stereoselective}, issn = {0040-4039}, doi = {10.1016/j.tetlet.2011.05.051}, author = {Patil, Madhuri T. and Krishnaswamy, Shobhana and Sarmah, Manash P. and Shashidhar, Mysore S.} } @article { ISI:000294593400012, title = {Thermal epimerization of inositol 1,3-benzylidene acetals in the molten state}, journal = {Tetrahedron}, volume = {67}, number = {38}, year = {2011}, month = {SEP}, pages = {7280-7288}, publisher = {PERGAMON-ELSEVIER SCIENCE LTD}, address = {THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND}, abstract = {

1,3-O-Benzylidene-2,4,5,6-tetra-O-substituted-myo-inositol derivatives obtained by the DIBAL-H reduction of the corresponding myo-inositol 1,3,5-orthobenzoate derivatives undergo epimerization at the acetal carbon on heating, in the molten state, just above their melting point. The same epimerization reaction does not proceed either in the crystalline state or in solution. DFT calculations suggest that the epimeric acetal obtained by this thermal process is relatively more stable than the starting acetal. Either of these acetals could not be obtained by the reaction of the corresponding inositol derived diol with benzaldehyde. These observations constitute a novel reaction solely in the molten state, which are rarely encountered in the literature. X-ray crystal structures of the epimeric acetals as well as their radical deoxygenation reaction are also reported. (C) 2011 Elsevier Ltd. All rights reserved.

}, keywords = {cyclitols, Deoxygenation, Epimerization, Melt, Xanthate}, issn = {0040-4020}, doi = {10.1016/j.tet.2011.07.044}, author = {Gurale, Bharat P. and Krishnaswamy, Shobhana and Vanka, Kumar and Shashidhar, Mysore S.} } @article { ISI:000310467600030, title = {Achieving molecular stability of racemic 4-O-benzyl-myo-inositol-1,3,5-orthoformate through crystal formation}, journal = {Crystengcomm}, volume = {14}, number = {23}, year = {2012}, month = {AUG}, pages = {8010-8016}, publisher = {ROYAL SOC CHEMISTRY}, address = {THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND}, abstract = {

Molecular stability of racemic 4-O-benzyl-myo-inositol-1,3,5-orthoformate, an early intermediate during the synthesis of phosphoinositols, depends on the phase in which it is stored. This orthoformate is stable when stored in the crystalline form or as solution in common organic solvents. The former has eluded chemists since the preparation of this benzyl ether two decades ago. The difficulty in obtaining crystals of this orthoformate is due to the cleavage of the orthoformate moiety during storage in the gummy state. Dimorphs (form I and form II) of crystalline racemic 4-O-benzyl-myo-inositol-1,3,5-orthoformate, were obtained when the gummy sample was stored over extended periods of time. Form I crystals could be obtained consistently, by crystallization of a frozen (-20 degrees C) solid sample, from a solution of dichloromethane- light petroleum. The two crystal forms display dissimilar patterns of hydrogen bonding and molecular assembly in the solid-state.

}, issn = {1466-8033}, doi = {10.1039/c2ce26199e}, author = {Sardessai, Richa and Krishnaswamy, Shobhana and Shashidhar, Mysore S.} } @article {42806, title = {Evaluation of viability of halogen{\textbullet}{\textbullet}{\textbullet}O2N interactions: insight form crystal packing in a series of isomeric halo and nitro substituted triaryl compounds with modular positioning of halogen and NO2 groups}, journal = {CrystEngComm}, volume = {15}, year = {2013}, month = {APR}, pages = {5283-5300}, abstract = {

A series of isomeric triaryl compounds with a modular positioning of the halogen and NO2 groups have been synthesized by the azide{\textendash}alkyne {\textquotedblleft}click reaction{\textquotedblright} and have been characterized by single crystal X-ray structure analysis. This isomeric series has provided an opportunity for understanding the efficiency of the bifurcated halogen...NO2 synthon in the organization of the molecules in the crystalline lattice. The changes in molecular conformation, crystal packing and supramolecular aggregation due to the change in the relative positioning of the complementary groups, halogen atom and the NO2 group on ring A and ring C respectively, have been discussed. All the isomers synthesized are crystalline and establish the triazole as a reliable linker for crystal engineering oriented molecular synthesis. The 2-NO2 derivatives display in general, a helical architecture and 3-NO2 derivatives exhibit a centrosymmetric dimeric assembly via the complementary C{\textendash}H...O interactions leading to either a helical or a 2-dimensional sheet pattern. The molecular organization in 4-NO2 derivatives revealed in general a 2D sheet pattern.

}, doi = {10.1039/C3CE40192H}, author = {Ramana, Chepuri V. and Goriya, Yogesh and Durugkar, Kulbhushan A. and Chatterjee, Soumitra and Krishnaswamy, Shobhana and Gonnade, Rajesh G.} } @article { ISI:000324316300042, title = {Identification of molecular crystals capable of undergoing an acyl-transfer reaction based on intermolecular interactions in the crystal lattice}, journal = {Chemistry-A European Journal}, volume = {19}, number = {38}, year = {2013}, month = {SEP}, pages = {12867-12874}, publisher = {WILEY-V C H VERLAG GMBH}, address = {BOSCHSTRASSE 12, D-69469 WEINHEIM, GERMANY}, abstract = {

Investigation of the intermolecular acyl-transfer reactivity in molecular crystals of myo-inositol orthoester derivatives and its correlation with crystal structures enabled us to identify the essential parameters to support efficient acyl-transfer reactions in crystals: 1)the favorable geometry of the nucleophile (OH) and the electrophile (CO) and 2)the molecular assembly, reinforced by CH interactions, which supports a domino-type reaction in crystals. These parameters were used to identify another reactive crystal through a data-mining study of the Cambridge Structural Database. A 2:1 co-crystal of 2,3-naphthalene diol and its di-p-methylbenzoate was selected as a potentially reactive crystal and its reactivity was tested by heating the co-crystals in the presence of solid sodium carbonate. A facile intermolecular p-toluoyl group transfer was observed as predicted. The successful identification of reactive crystals opens up a new method for the detection of molecular crystals capable of exhibiting acyl-transfer reactivity.

}, keywords = {Acylation, domino reactions, intermolecular interactions, solid-state reactions, X-ray diffraction}, issn = {0947-6539}, doi = {10.1002/chem.201301058}, author = {Tamboli, Majid I. and Krishnaswamy, Shobhana and Gonnade, Rajesh G. and Shashidhar, Mysore S.} } @article { ISI:000319647600012, title = {Orientation of the beta-hydroxyl group controls the diastereoselectivity during the hydride reduction and grignard reaction of inososes}, journal = {Tetrahedron}, volume = {69}, number = {25}, year = {2013}, month = {JUN}, pages = {5144-5151}, publisher = {PERGAMON-ELSEVIER SCIENCE LTD}, address = {THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND}, abstract = {

A comparison of the results of the Grignard reaction and the hydride reduction of the carbonyl group of epi- and scyllo-inososes reveals that the extent of diastereoselectivity of these reactions is decided by the orientation of the beta-hydroxyl group (or its derivative). Presence of an axial beta-hydroxyl group generally results in the formation of relatively larger amount of the axial alcohol as a result of the reduction of the carbonyl group. The possible reasons for the observed differences in diastereoselectivity between the reactions of these isomeric epi- and scyllo-inososes have been discussed. The sequence of reactions reported here provides convenient access to C-allcylated inositols, such as iso-laminitol and iso-mytilitol as well as 2-O-methyl epi-inositol, an epimer of the naturally occurring ononitol. (C) 2013 Elsevier Ltd. All rights reserved.

}, keywords = {Cyclitol, diastereoselectivity, Grignard, Inositol, Nucleophile, reduction}, issn = {0040-4020}, doi = {10.1016/j.tet.2013.04.081}, author = {Jagdhane, Rajendra C. and Patil, Madhuri T. and Krishnaswamy, Shobhana and Shashidhar, Mysore S.} } @article { ISI:000342609300017, title = {Crystal-to-crystal thermal phase transformation of polymorphs of isomeric 2,3-naphthalene diol ditoluates: mechanism and implications for molecular crystal formation and melting}, journal = {Crystal Growth \& Design}, volume = {14}, number = {10}, year = {2014}, month = {OCT}, pages = {4985-4996}, publisher = {AMER CHEMICAL SOC}, type = {Article}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {

Isomeric para- (1) and meta- (2) ditoluate derivatives of naphthalene 2,3-diol exhibited polymorphism producing three (Forms 1I, 1II, 1III) and two (Forms 2I, 2II) polymorphs each, respectively, depending on the solvent and conditions of crystallization. Crystal forms 1I, 1II, and 2I could be obtained repeatedly, whereas crystal forms 1III and 2II were obtained (separately) in one of the crystallization experiments, each. All the crystal forms were stable at ambient conditions, except for Form 2II, which disintegrated to a powder over 45 days. In contrast, the ortho-ditoluate (3) of naphthalene 2,3-diol did not exhibit polymorphism; it yielded fibrous chiral crystals from different solvents/conditions. Crystal structure analysis of all these polymorphs revealed dominance of energetically similar weak intermolecular interactions such as CH center dot center dot center dot O, CH center dot center dot center dot pi, pi center dot center dot center dot pi, and their interplay in molecular aggregation resulting in polymorphic modifications. Differential scanning calorimetry (DSC), hot stage microscopy, single crystal and powder X-ray diffraction measurements revealed crystal-to-crystal thermal transformation of Forms 1I and 1II crystals to Form 1III crystals and Form 2II crystals to Form 2I crystals. The transformation of Form 1I and Form 1II crystals to Form 1III crystals can be viewed as progressive destabilization of the crystal lattice during heating and converting to metastable phase, whereas the conversion of Form 2II to Form 2I crystals can be considered as reorganization of an unstable crystalline phase to a stable crystalline phase. Hence comparative studies of the structure of stable, metastable, or transient crystals and crystal-to-crystal transformations involving these forms could aid in unraveling the process of crystallization.

}, issn = {1528-7483}, doi = {10.1021/cg5005227}, author = {Tamboli, Majid I. and Krishnaswamy, Shobhana and Gonnade, Rajesh G. and Shashidhar, Mysore S.} } @article { ISI:000361190200026, title = {Intramolecular cyclization of carbonate and thiocarbonate derivatives of myo-inositol in the solid state: implications for acyl group transfer reactions in molecular crystals}, journal = {Chemistry-A European Journal}, volume = {21}, number = {39}, year = {2015}, month = {SEP}, pages = {13676-13682}, publisher = {WILEY-V C H VERLAG GMBH}, address = {POSTFACH 101161, 69451 WEINHEIM, GERMANY}, abstract = {

Racemic 4-O-phenoxycarbonyl and 4-O-phenoxythiocarbonyl derivatives of myo-inositol orthoformate undergo thermal intramolecular cyclization in the solid state to yield the corresponding 4,6-bridged carbonates and thiocarbonates, respectively. The thermal cyclization also occurs in the solution and molten states, but less efficiently, suggesting that these cyclization reactions are aided by molecular pre-organization, although not strictly topochemically controlled. Crystal structures of two carbonates and a thiocarbonate clearly revealed that the relative orientation of the electrophile and the nucleophile in the crystal lattice facilitates the intramolecular cyclization reaction and forbids the intermolecular reaction. The correlation observed between the chemical reactivity and the non-covalent interactions in the crystal of the reactants provides a way to estimate the chemical stability of analogous molecules in the solid state.

}, keywords = {crystal engineering, cyclitols, inositols, nucleophilic substitution, solid-phase synthesis}, issn = {0947-6539}, doi = {10.1002/chem.201501480}, author = {Tamboli, Majid I. and Shashidhar, Mysore S. and Gonnade, Rajesh G. and Krishnaswamy, Shobhana} } @article {43509, title = {Helical preorganization of molecules drives solid-state intermolecular acyl-transfer reactivity in crystals: structures and reactivity studies of solvates of racemic 2,6-Di-O-(4-fluorobenzoyl)-myo-inositol 1,3,5-orthoformate}, journal = {Crystal Growth \& Design}, volume = {17}, year = {2017}, month = {JAN}, pages = {117-126}, abstract = {Racemic 2,6-di-O-(4-fluorobenzoyl)-myo-inositol 1,3,5-orthoformate yielded structurally dissimilar solvent-free and solvated crystals depending upon the solvent of crystallization. The solvated crystals exhibited helical assembly of host molecules, due to the interaction of the guest molecules with the orthoformate moiety of the host. Some of the solvates showed specific but incomplete benzoyl group transfer reactivity below the phase transition temperature, whereas the reaction in solvent-free crystals led to a mixture of several products. These results reveal the necessity of helical molecular packing of the reacting molecules in their crystals to facilitate specific intermolecular acyl transfer reactivity. The crystal, structures of the fluorobenzoate solvates were similar to those of the solvates of the analogous chloro and bromobenzoates. The latter could be thermally :transformed into their solvent-free form via melt crystallization, resulting in the conversion of a helical molecular packing into a nonhelical molecular packing.}, doi = {10.1021/acs.cgd.6b01322}, author = {Krishnaswamy, Shobhana and Shashidhar, Mysore S. and Bhadbhade, Mohan M.} } @article {44440, title = {Correlation of intermolecular acyl transfer reactivity with noncovalent lattice interactions in molecular crystals: toward prediction of reactivity of organic molecules in the solid state}, journal = {Journal of Organic Chemistry}, volume = {83}, year = {2018}, month = {APR}, pages = {3952-3959}, abstract = {Intermolecular acyl transfer reactivity in several molecular Acyl transfer reactivity can be predicted in solution based crystals was studied, and the outcome of the reactivity was analyzed in the light of structural information obtained from the crystals of the reactants. in solid state Minor changes in the molecular structure resulted in significant variations in the noncovalent interactions and packing of molecules in the crystal lattice, which drastically affected the facility of the intermolecular acyl transfer reactivity in these crystals. Analysis of the reactivity vs crystal structure data revealed dependence of the reactivity on electrophile ... nucleophile interactions and C-H center dot center dot center dot pi interactions between the reacting molecules. The presence of these noncovalent interactions augmented the acyl transfer reactivity, while their absence hindered the reactivity of the molecules in the crystal. The validity of these correlations allows the prediction of intermolecular acyl transfer reactivity in crystals and co-crystals of unknown reactivity. This crystal structure-reactivity correlation parallels the molecular structure-reactivity correlation in solution-state reactions, widely accepted as organic functional group transformations, and sets the stage for the development of a similar approach for reactions in the solid state.}, doi = {10.1021/acs.joc.8b00293}, author = {Krishnaswamy, Shobhana and Shashidhar, Mysore S.} } @article {46222, title = { Intermolecular acyl-transfer reactions in molecular crystals }, journal = {Accounts of Chemical Research}, volume = {52}, year = {2019}, month = {FEB}, pages = {437-446}, type = {Article}, abstract = {

CONSPECTUS: It is far more difficult to recognize and predict the chemical reactions that a molecule of an organic compound can undergo in crystalline (solid) state as compared to the solution state (the "organic functional group" approach), since the published data on solid-state structure reactivity investigations and correlations are scant. The discovery of the first intermolecular acyl-transfer reaction in molecular crystals of racemic 2,4-di-O-benzoyl-myo-inositol-1,3,5-orthoformate (DiBz) during our attempts to develop methods for the synthesis of phosphoinositols, motivated us to find other molecular crystals capable of supporting similar reactions. Small changes to the molecular structure of DiBz yielded analogues with different crystal structures which showed varying degrees of acyl transfer reactivity as compared to the crystals of DiBz. A systematic investigation of the structures, polymorphism, cocrystallization behavior, and the corresponding reactivity of these crystals allowed us to correlate the acyl transfer reactivity with their structures and inherent noncovalent interactions and provided crucial insights into the mechanism of these reactions. Polymorphs or cocrystals of these compounds exhibited dissimilar reactivities due to differences in the molecular conformation and/or arrangements in their crystals. The knowledge of phase transitions between polymorphs enabled us to control and tune the reactivity in the solid state. We could identify three conditions essential for intermolecular acyl transfer: (i) favorable relative geometry of the electrophile (ester C=O) and the nucleophile (OH), (ii) noncovalent interactions (C-H center dot center dot center dot pi) between the reacting molecules which help in maintaining the facility and specificity of the reaction, and (iii) the presence of channels in the lattice which enable propagation of the reaction in the crystal. Based on this supramolecular structure reactivity correlation, we identified other molecular crystals (composed of molecules of widely different molecular structure from that of DiBz) from a survey of the Cambridge Structural Database (CSD) and predicted their acyl transfer reactivity. The increased availability of user-friendly modern X-ray diffractometers and related software has enabled efficient collection, analysis and interpretation of single crystal X-ray diffraction data, essential for such studies. The rapidly expanding CSD facilitates the identification of crystals with similar structures and reactivity patterns. In a wider perspective, facile reactions in molecular crystals fascinate chemists because these reactions usually exhibit unique product selectivity and have the potential to be developed as sustainable green reactions. We are optimistic that similar approaches for the study of other group transfer reactions in molecular crystals would augment and widen the scope of chemical reactions in molecular crystals in particular and the solid state in general. The ability to predict the reactivity of molecules in their crystals could find applications in organic synthesis, material science and industry. Realization of the involvement of inositol derivatives in cellular processes led to the discovery of cellular signal transduction mechanisms. The ability of inositol derivatives to support facile acyl-transfer reactions in the crystalline state might well have opened a new avenue for research in the area of organic solid-state reactions.

}, doi = {10.1021/acs.accounts.8b00557}, author = {Shashidhar, Mysore S. and Krishnaswamy, Shobhana} } @article {47631, title = {Construction of two-component chemically reactive supramolecular assemblies-acyl migration reactions in cocrystals of napthalene-2,3-diol and its diesters}, journal = {ChemPlusChem}, volume = {86}, year = {2021}, month = {AUG}, pages = {1128-1134}, type = {Article}, abstract = {Reactions in solids are of contemporary interest due to applications in pharmaceutical industries to environmental sustainability. Although several reactive crystals that support chemical reactions have been identified and characterized, the same cannot be said about reactive cocrystals. Earlier we correlated the facile acyl group transfer reactions in crystals with supramolecular parameters obtained from the crystal structures. The structure-reactivity correlation revealed the requirement of proper juxtaposition of electrophile (C=O) and the nucleophile (OH) with distance (similar to 3.2 angstrom) and angle (similar to 90 degrees) along the chain structure. The current article describes the preparation of cocrystals that are capable of supporting intermolecular acyl group transfer reactions in a group of structurally similar molecules. The cocrystals of naphthalene 2,3-diol and its corresponding diesters showed a facile solid state acyl transfer reaction, which has been well correlated with their crystal structures.}, keywords = {Acylation, domino reactions, intermolecular interactions, reaction in cocrystal, solid-state reactions, X-ray diffraction}, issn = {2192-6506}, doi = {10.1002/cplu.202100139}, author = {Bahadur, Vir and Gonnade, Rajesh G. and Tamboli, I. Majid and Krishnaswamy, Shobhana and Shashidhar, Mysore S.} }