@article {44204, title = {Beyond hydrofunctionalisation: a well-defined calcium compound catalysed mild and efficient carbonyl cyanosilylation}, journal = {Chemistry-A European Journal}, volume = {24}, year = {2018}, month = {JAN}, pages = {1269-1273}, type = {Article}, abstract = {

Organocalcium compounds have been reported as efficient catalysts for various transformations, for cases in which one of the substrates contained an E-H (E=B, N, Si, P) bond. Here, we look at the possibility of employing an organocalcium compound for a transformation in which none of the precursors has a polar E-H bond. This study demonstrates the utilization of a well-defined amidinatocalcium iodide, [PhC(NiPr)(2)CaI] (1) for cyanosilylation of a variety of aldehydes and ketones with Me3SiCN under ambient conditions without the need of any co-catalyst. The reaction mechanism involves a weak adduct formation between 1 and Me3SiCN leading to the activation of the Si-C bond, which subsequently undergoes sigma-bond metathesis with a C=O moiety. Such a mechanistic pathway is unprecedented in alkaline earth metal chemistry. Experimental and computational studies support the mechanism.

}, keywords = {Ca catalysis, carbonyls, cyanosilylation, Density functional calculations, transition-metal free}, issn = {0947-6539}, doi = {10.1002/chem.201705795}, author = {Yadav, Sandeep and Dixit, Ruchi and Vanka, Kumar and Sen, Sakya S.} } @article {46776, title = {Catalytic reductive deoxygenation of esters to ethers driven by hydrosilane activation through non-covalent interactions with a fluorinated borate salt}, journal = {Catalysis Science \& Technology}, volume = {10}, year = {2020}, month = {JUL}, pages = {4586-4592}, type = {Article}, abstract = {

We report the catalytic and transition metal-free reductive deoxygenation of esters to ethers through the use of a hydrosilane and a fluorinated borate BArF salt as a catalyst. Experimental and theoretical studies support the role of noncovalent interactions between the fluorinated catalyst, the hydrosilane and the ester substrate in the reaction mechanism.

}, issn = {2044-4753}, doi = {10.1039/d0cy00775g}, author = {Rysak, Vincent and Dixit, Ruchi and Trivelli, Xavier and Merle, Nicolas and Agbossou-Niedercorn, Francine and Vanka, Kumar and Michon, Christophe} } @article {46650, title = {Total synthesis of beshanzuenone D and its epimers and abiespiroside A}, journal = {Organic Letters}, volume = {22}, year = {2020}, month = {NOV }, pages = {8561-8565}, type = {Article}, abstract = {

A unified and protecting-group-free six-step total synthesis of bisabolane-type sesquiterpenoid beshanzuenone D and its stereoisomers and abiespiroside A using S-(+)-carvone as a common chiral-pool building block is disclosed. This synthetic route features chemoselective allylic chlorination of carvone, Au(I)-catalyzed cydoisomerization induced construction of furan from homopropargylic diol, substrate-controlled selective hydroxylation using Davis-oxaziridine, and dye-sensitized photo-oxidation (through O-1(2)) of hydroxyalkyl tethered furan to access oxaspirolactone as key transformations. A comprehensive set of NMR data along with DFT calculations, ECD spectra, and optical rotation measurements of the synthesized beshanzuenone D and its epimers were obtained to confirm absolute configurations.

}, issn = {1523-7060}, doi = {10.1021/acs.orglett.0c03157}, author = {Borade, Balasaheb R. and Dixit, Ruchi and Kontham, Ravindar} } @article {46982, title = {Tris-heteroleptic ruthenium(II) polypyridyl complexes: Synthesis, structural characterization, photophysical, electrochemistry and biological properties}, journal = {Journal of Inorganic Biochemistry}, volume = {203}, year = {2020}, month = {FEB}, pages = {110903}, type = {Article}, abstract = {

{Three water-soluble tris-heteroleptic ruthenium(II) polypyridyl complexes [Ru(bpy)(phen)(bpg)](2+) (1), [Ru (bpy)(dppz)(bpg)]2+ (2), and [Ru(phen)(dppz)(bpg)]2+ (3) (where bpy = 2,2{\textquoteright}-bipyridine

}, keywords = {Circular dichroism, Cytotoxicity, fluorescence, Polypyridyl, ruthenium}, issn = {0162-0134}, doi = {10.1016/j.jinorgbio.2019.110903}, author = {Bhat, Satish S. and Kumbhar, Avinash S. and Purandare, Neeraja and Khan, Ayesha and Grampp, Gunter and Loennecke, Peter and Hey-Hawkins, Evamarie and Dixit, Ruchi and Vanka, Kumar} } @article {47388, title = {Easy and practical approach to access multifunctional cylcopentadiene- and cyclopentene-spirooxindoles via [3+2] annulation}, journal = {Organic \& Biomolecular Chemistry}, volume = {19}, year = {2021}, month = {MAY}, pages = {4338-4345}, type = {Article}, abstract = {

A highly regioselective [3 + 2] annulation of Morita-Baylis-Hillman (MBH) carbonates of isatin with aurone/thioaurone is developed. Spiroheterocycles such as spirooxindole cyclopentadiene and spirooxindole fused hydroxy cyclopentene derivatives are constructed in one pot by exploring the reactivity of Lewis bases. Combined experimental and density functional theory (DFT) calculations offered an insight into the reaction mechanism.

}, issn = {1477-0520}, doi = {10.1039/d1ob00514f, Early Access Date = APR 2021}, author = {Warghude, Prakash K. and Sabale, Abhijeet S. and Dixit, Ruchi and Vanka, Kumar and Bhat, Ramakrishna G.} } @article {47382, title = {Substrate, catalyst, and solvent: the triune nature of multitasking reagents in hydroboration and cyanosilylation}, journal = {Organometallics}, volume = {40}, year = {2021}, month = {APR}, pages = {1104-1112}, type = {Article}, abstract = {

A truly green chemical process would avoid the use of an external catalyst, while still achieving high efficiency. This has been realized in the very recent past for hydroboration, cyanosilylation, acetalization, and the aza-Michael addition, among other reactions. The current combined computational and experimental study unlocks the secret to how this highly desirable outcome is accomplished: one of the reactants in the process also acts as the catalyst. Specifically, this is shown (i) for the important hydroboration reaction, with pinacolborane (HBpin) as the hydroborating reagent and benzaldehyde, acetophenone, benzoic acid and p-methoxyphenylacetylene as the hydroborated substrates, and (ii) for cyanosilylation, with trimethylcyanosilane (TMSCN) as the cyanosilylating agent and benzaldehyde as the substrate. The mechanistic understanding thus gained has then been further exploited experimentally to bring hydroboration and cyanosilylation closer to experimental conditions in catalysis. These insights can potentially be expanded to the rapidly growing area of solvent-free and internal catalyst chemistry.

}, issn = {0276-7333}, doi = {10.1021/acs.organomet.1c00070}, author = {Dixit, Ruchi and Bisai, Milan Kumar and Yadav, Sandeep and Yadav, Vinita and Sen, Sakya S. and Vanka, Kumar} } @article {47605, title = {Synthesis of four diastereomers of notoryne and their C-13 NMR chemical shifts analysis}, journal = {Journal of Chemical Sciences}, volume = {133}, year = {2021}, month = {SEP}, pages = {76}, type = {Article}, abstract = {In this manuscript we document the details of the synthesis of four diastereomers of notoryne. The synthesis of one of the diastereomer having a similar relative stereochemistry of substituents on the both THF rings like notoryne, however, being the relative stereochemistry between the bridging carbon of these two THF units is changed from anti to syn has been executed mainly to learn how the ring carbon chemical shifts vary with this change. Interestingly, the deviations are found mainly for the carbons of THF ring that bears the Br-group. In addition to this isomer, three more diastereomers having the relative stereochemistry of substituents on either of the THF rings varied have been also synthesized. All four diastereomers have been subjected for extensive NMR studies and their C-13 NMR chemical shifts have been compared with notoryne and laurendecumenyne B. In addition, chemical shifts for the four diastereomers along with these natural products were calculated with the help of DFT calculations and compared to the experimentally obtained chemical shift values.}, issn = {0974-3626}, doi = {10.1007/s12039-021-01929-y}, author = {Senapati, Sibadatta and Das, Shyamsundar and Dixit, Ruchi and Vanka, Kumar and Ramana, V, Chepuri} } @article {48405, title = {Silver dependent enantiodivergent gold(i) catalysed asymmetric intramolecular hydroamination of alkenes: a theoretical study}, journal = {Catalysts}, volume = {12}, year = {2022}, month = {NOV}, pages = {1392}, type = {Article}, abstract = {

We report a theoretical study of the first silver-dependent enantiodivergent gold-catalysed reaction. The combination of a single chiral binuclear gold(I) chloride complex and silver perchlorate catalyses the asymmetric intramolecular hydroamination of alkenes and affords both enantiomers of the products by applying a simple solvent change from toluene to methanol. A gold-silver chloride adduct that occurs only in methanol appears to control the enantioinversion. If one gold atom coordinates and activates the alkene moiety, the other gold is included in an adduct with silver chloride, which coordinates a methanol solvent molecule and further interacts with the amine function. If the use of toluene implies free anions and affords (S)-enantiomer, methanol allows a proximal interaction with the amine, leads to an opposite stereodifferentiation of the two diastereomeric intermediates during the final protodeauration step and results in the (R)-enantiomer.

}, keywords = {alkene, enantiodivergent catalysis, Gold, hydroamination, Silver}, doi = {10.3390/catal12111392}, author = {Dixit, Ruchi and Sharma, Himanshu and Agbossou-Niedercorn, Francine and Vanka, Kumar and Michon, Christophe} } @article {48162, title = {Versatile chemistry of six-membered NHC with boranes: bromination at sp(3) borane, activation of the B-H bond of HBpin, and ring expansion of NHC}, journal = {Dalton Transactions}, volume = {51}, year = {2022}, month = {OCT}, pages = {14452-14457}, type = {Article}, abstract = {

The NHC.borane chemistry has been majorly restricted to imidazol-2-ylidene classes of carbenes. In our previous communication, we reported the synthesis of 6-SIDipp center dot BH3 [6-SIDipp = 1,3-di(2,6-diisopropylphenyl) tetrahydropyrimidine-2-ylidene] and its electrophilic substitution reaction with iodine. Here, we have shown selective bromination of a 6-SIDipp stabilized sp(3) B-H bond. Treatment of 1.2 equivalents of N-bromosuccinamide with 6-SIDipp center dot BH3 gives a mixture of mono- and disubstituted products 6-SIDipp center dot BH2Br (1) and 6-SIDipp center dot BHBr2 (2). However, the reactions with alkyl bromides or carbon tetrabromide resulted in 6-SIDipp center dot BH2Br (1) selectively. Exploration of the chemistry of 6-SIDipp with BHCl2 and 9-BBN (9-borabicyclo[3.3.1]nonane) led to mono-6-SIDipp adducts 3 and 6a. Furthermore, 6a undergoes ring expansion to afford a seven-membered product, 6b, under mild conditions. Unlike BHCl2 or 9-BBN, the B-H bond of HBpin undergoes oxidative addition upon reaction with 6-SIDipp, epitomizing the first example (7) of a B-H bond insertion at NHCs. The analogous reactivity with HBcat led to a tetra-hydropyrimidinium salt with B(cat)(2) as a counteranion (8).

}, issn = {1477-9226}, doi = {10.1039/d2dt01707e}, author = {Kundu, Gargi and Dixit, Ruchi and Tothadi, Srinu and Vanka, Kumar and Sen, Sakya S.} } @article {48451, title = {Oligothiophene-ring-strapped perylene bisimides: functionalizable coaxial donor-acceptor macrocycles}, journal = {Angewandte Chemie-International Edition}, volume = {62}, year = {2023}, month = {JAN}, type = {Article}, abstract = {

Aesthetic designs from nature enable new knowledge to be gained and, at the same time, inspire scientific models. In this context, multicomponent macrocycles embody the advantage of precisely positioning the structural units to achieve efficient communication between them. However, the construction of a functionalizable macrocycle for ultrafast charge separation and stabilization has not been attempted. Herein, we report the synthesis, crystal structure, and transient absorption of a new functionalizable macrocycle consisting of an oligothiophene-ring-strapped perylene bisimide. Transient absorption results point to a sequential improvement in charge separation and stabilization from the macrocycle to the corresponding linear dimer and 2D polymer due to the unique design. Our macrocycle design with a supportive spatial arrangement of the donor and acceptor units will inspire the development of more complex synthetic systems with exciting electron-transfer and charge-separation features.

}, keywords = {Charge Separation, Donor-Acceptor Systems, Electron Transfer, Macrocycles, Perylene Bisimides}, issn = {1433-7851}, doi = {10.1002/anie.202212934}, author = {Dnyaneshwar Veer, Sairam and Chandrakant Wakchaure, Vivek and Asokan, Kiran and Dixit, Ruchi and Goswami, Tanmay and Saha, Ramchandra and Gonnade, Rajesh and Ghosh, Hirendra N. and Santhosh Babu, Sukumaran} } @article {48746, title = {Visible-light-active unsymmetrical squaraine dyes with 1 V of open-circuit voltage for dye-sensitized solar cells}, journal = {ChemPhotoChem}, volume = {7}, year = {2023}, month = {MAY}, type = {Article}, abstract = {

A series of alkyl-group-functionalized, aniline- and indoline-donor-based, unsymmetrical visible-light-active squaraine dyes, AM1-3, were designed and synthesized. Dye-sensitized solar cell (DSSC) devices were fabricated with both I-/I-3(-) and [Cu(tmby)(2)](+/2+) electrolytes. DSSC devices sensitized with the AM1 and AM2 dyes showed relatively high-power conversion efficiency of 7.44 \% and 7.22 \%, respectively with I-/I-3(-) in the absence of chenodeoxycholic acid (CDCA) than those of the AM3 dye (5.41 \%). The [Cu(tmby)(2)](+/2+) electrolyte along with poly(3,4-ethylenedioxythiophene) (PEDOT) as cathode material showed excellent open-circuit potentials (V-OC) of 1030, 1025, and 1001 mV with the DSSC efficiency of 8.05 \%, 7.96 \%, and 5.84 \%, respectively, for the AM1, AM2, and AM3 dyes in the absence of CDCA. Here, the AM1 dye exhibited the maximum DSSC efficiency of 8.05 \% and V-OC of 1030 mV, which is the highest obtained efficiency and V-OC for the visible-light active zwitterionic unsymmetrical-squaraine dye with copper-based electrolyte.

}, keywords = {Cu electrolytes, dihedral angle, Dye-sensitized solar cells, open circuit voltage, squaraine dyes}, issn = {2367-0932}, doi = {10.1002/cptc.202200328}, author = {Singh, Amrita and Kumar Singh, Ambarish and Dixit, Ruchi and Vanka, Kumar and Krishnamoorthy, Kothandam and Nithyanandhan, Jayaraj} }