@article { ISI:000318589100018, title = {Metal or nonmetal cooperation with a phenyl group: route to catalysis? a computational investigation}, journal = {ACS Catalysis}, volume = {3}, number = {5}, year = {2013}, month = {MAY}, pages = {920-927}, publisher = {AMER CHEMICAL SOC}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {

Full quantum mechanical calculations demonstrate that cooperativity in the form of the activation of the M-C bond (M: transition metal or boron, C: the ipso carbon of the coordinated phenyl group) can lead to effective catalysis pathways. Calculations show that the presence of an aromatic bidentate ligand attached to a transition metal, or even a main group element, such as boron, can lead to effective catalysts for,a, range of important reactions, such as the dehydrogenation of ammonia borane and formic acid and the activation of the N-H, bond in aromatic amities. Moreover, it is shown that the design of tridentate pincer complexes with the aromatic group at a terminal end can lead to effective M-C cooperativity. As such, the current work introduces a new concept in cooperativity and bond activation chemistry.

}, keywords = {catalysis, Density functional theory, metal-ligand cooperativity, small molecule activation}, issn = {2155-5435}, doi = {10.1021/cs400174u}, author = {Ghatak, Kamalika and Mane, Manoj and Vanka, Kumar} } @article { ISI:000351849100002, title = {Can substituted allenes be highly efficient leaving groups in catalytic processes? a computational investigation}, journal = {Journal of Computational Chemistry}, volume = {36}, number = {11}, year = {2015}, month = {APR}, pages = {795-804}, publisher = {WILEY-BLACKWELL}, address = {111 RIVER ST, HOBOKEN 07030-5774, NJ USA}, abstract = {

There is considerable interest presently in the chemistry of allenes. The current computational investigation looks into the possibility of using allenes and their derivatives as leaving groups. As it is well known, leaving groups are significant in catalytic processes for generating the active site. A full quantum mechanical study using density functional theory shows that allenes and their derivatives can function as excellent leaving groups. Indeed, the calculations show that they can be several orders of magnitude more effective than existing ligands for this purpose. The modification of second generation Grubbs{\textquoteright} catalysts with these ligands suggests that the allene ligand cases that would be most effective are those having electron withdrawing groups, especially those that have the potential for supramolecular interactions between the substituent groups in the free state. (c) 2015 Wiley Periodicals, Inc.

}, keywords = {allenes, carbones, Density functional theory, olefin metathesis, supramolecular interactions}, issn = {0192-8651}, doi = {10.1002/jcc.23855}, author = {Kuriakose, Nishamol and Vanka, Kumar} } @article {44624, title = {B(C6F5)(3): catalyst or initiator? insights from computational studies into surrogate silicon chemistry}, journal = {ACS Catalysis}, volume = {8}, year = {2018}, month = {JUL}, pages = {6163-6176}, type = {Article}, abstract = {

One of the most promising recent developments in catalysis has been the use of the metal-free Lewis acid B(C6F5)(3) as a catalyst for a range of different chemical transformations. Perhaps the most impressive achievement in this regard is the recently accomplished in situ generation of SiH4 from surrogates (Simonneau and Oestreich, Nat. Chem., 2015,7, 816). However, what the current computational work, with density functional theory, reveals is that this process, in addition to being catalyzed by B(C6F5)(3), is also significantly dominated by a series of autocatalytic reactions. The results are further corroborated by the use of the energetic span model, which shows that the turnover frequency is higher for the newly proposed autocatalytic pathway in comparison to the conventional B(C6F5)(3)-catalyzed pathway. The current work therefore provides interesting new insights into surrogate silicon chemistry. But, more importantly, the current studies indicate that B(C6F5)(3) is likely to function more as an initiator rather than a pure catalyst in many metal-free transformations that have been reported to date.

}, keywords = {autocatalysis, Density functional theory, ion-pair, Lewis acid catalysis, reaction mechanism, surrogate silicone chemistry, tris(pentafluorophenyl)borane}, issn = {2155-5435}, doi = {10.1021/acscatal.7b04489}, author = {Banerjee, Subhrashis and Vanka, Kumar} } @article {47602, title = {Insights into chemical reactions at the beginning of the universe: from HeH+ to H-3 (+)}, journal = {Frontiers in Chemistry}, volume = {9}, year = {2021}, month = {JUN }, pages = {679750}, type = {Article}, abstract = {At the dawn of the Universe, the ions of the light elements produced in the Big Bang nucleosynthesis recombined with each other. In our present study, we have tried to mimic the conditions in the early Universe to show how the recombination process would have led to the formation of the first ever formed diatomic species of the Universe: HeH+, as well as the subsequent processes that would have led to the formation of the simplest triatomic species: H-3 (+). We have also studied some special cases: higher positive charge with fewer number of hydrogen atoms in a dense atmosphere, and the formation of unusual and interesting linear, dicationic He chains beginning from light elements He and H in a positively charged atmosphere. For all the simulations, the ab initio nanoreactor (AINR) dynamics method has been employed.}, keywords = {ab initio molecular dynamics, ab initio nanoreactor, Density functional theory, origin of molecules in the universe, the earliest lewis acid}, issn = {2296-2646}, doi = {10.3389/fchem.2021.679750}, author = {Dash, Soumya Ranjan and Das, Tamal and Vanka, Kumar} } @article {49044, title = {Role of aromatic alcohol additives on asymmetric organocatalysis reactions: insights from theory}, journal = {Chemistry-an asian jounrnal}, volume = {19}, year = {2024}, month = {FEB }, type = {Article}, abstract = {

The presence of an aromatic additive has been seen to enhance, often significantly, the enantioselectivity and yield in asymmetric organocatalysis. Considering their success across a dizzying range of organocatalysts and organic transformations, it would seem unlikely that a common principle exists for their functioning. However, the current investigations with DFT suggest a general principle: the phenolic additive sandwiches itself, through hydrogen bonding and pi \& sdot;\& sdot;\& sdot;pi stacking, between the organocatalyst coordinated electrophile and nucleophile. This is seen for a wide range of experimentally reported systems. That such complex formation leads to enhanced stereoselectivity is then demonstrated for two cases: the cinchona alkaloid complex (BzCPD), catalysing thiocyanation (2-naphthol additive employed), as well as for L-pipecolicacid catalysing the asymmetric nitroaldol reaction with a range of nitro-substituted phenol additives. These findings, indicating that dual catalysis takes place when phenolic additives are employed, are likely to have a significant impact on the field of asymmetric organocatalysis. The current DFT based study, on a wide range of organocatalysis systems, reveals a general principle by which phenolic additives influence asymmetric organocatalysis reactions. It is shown that the phenolic additive forms a sandwich complex, through hydrogen bonding and pi \& sdot;\& sdot;\& sdot;pi stacking interactions, with the organocatalyst coordinated electrophile and nucleophile, and enhances the enantioselectivity of the system as a result. image

}, keywords = {Additive, Asymmetric Organocatalysis, Cinchona Alkaloid, Density functional theory, Enantioselective Thiocyanation}, issn = {1861-4728}, doi = {10.1002/asia.202300997}, author = {Banerjee, Subhrashis and Vanka, Kumar} }