01982nas a2200241   4500008004100000022001400041245010800055210006900163260000800232300001400240490000600254520113500260653001801395653003001413653001301443653002501456653002301481653003301504653003401537100002501571700001701596856012701613       2018                        eng d  a2155-543500aB(C6F5)(3): catalyst or initiator? insights from computational studies into surrogate silicon chemistry0 aBC6F53 catalyst or initiator insights from computational studies  cJUL  a6163-61760 v83 a<p>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.</p>10aautocatalysis10aDensity functional theory10aion-pair10aLewis acid catalysis10areaction mechanism10asurrogate silicone chemistry10atris(pentafluorophenyl)borane1 aBanerjee, Subhrashis1 aVanka, Kumar  uhttps://library.ncl.res.in/content/bc6f53-catalyst-or-initiator-insights-computational-studies-surrogate-silicon-chemistry02385nas a2200205   4500008004100000022001400041245010100055210006900156260000900225490000700234520164100241653001301882653003101895653002201926653003001948653003501978100002502013700001702038856012402055       2024                        eng d  a1861-472800aRole of aromatic alcohol additives on asymmetric organocatalysis reactions: insights from theory0 aRole of aromatic alcohol additives on asymmetric organocatalysis  cFEB 0 v193 a<p>
	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 &amp; sdot;&amp; sdot;&amp; 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 &amp; sdot;&amp; sdot;&amp; sdot;pi stacking interactions, with the organocatalyst coordinated electrophile and nucleophile, and enhances the enantioselectivity of the system as a result. image</p>
10aAdditive10aAsymmetric Organocatalysis10aCinchona Alkaloid10aDensity functional theory10aEnantioselective Thiocyanation1 aBanerjee, Subhrashis1 aVanka, Kumar  uhttps://library.ncl.res.in/content/role-aromatic-alcohol-additives-asymmetric-organocatalysis-reactions-insights-theory