Theoretical Insights into Aluminum-Catalyzed Cyanosilylation of Aldehydes and Ketones

Abstract

Since main-group catalysts are more advantageous than transition metal catalysts from both economic and environmental viewpoints, their development and utilization, especially group 13 aluminum complexes for cyanosilylation of carbonyls, have drawn tremendous attention in recent years. Here, an extensive computational study is conducted to understand the mechanism of the cyanosilylation reaction catalyzed by organic aluminum complexes using density functional theory (DFT) calculations. Theoretical calculations suggest that the initial attack of trimethylsilyl cyanide (TMSCN) to the Al center is more facile over carbonyl coordination. Therefore, the catalytic cyanosilylation reaction follows a four-stage mechanism: initial coordination of TMSCN, carbonyl compound insertion, Si−C bond activation followed by carbonyl insertion, and finally, liberation of the desired cyanohydrin silyl ether. The Si−C bond activation step is identified to be the rate-determining step. The calculated activation barriers show nice correspondence with the experimental findings. Moreover, to elucidate the origin of activation barriers, energy decomposition analysis was accomplished for selected transition states. Among the neutral and cationic aluminum catalysts, LAlH(OTf) (C5) [L = HC(CMeN-Dipp) 2 , Dipp = 2,6-i Pr 2 C 6 H 3 ] and LAlMe + (C7) [L = ({(2,6-i Pr 2 C 6 H 3 N)-P(Ph 2 )} 2 N)] exhibit excellent catalytic reactivity toward cyanosilylation of both aldehydes and ketones.

Partial‐Interpenetration‐Controlled UiO‐Type Metal‐Organic Framework and its Catalytic Activity

“…This process is pivotal in cyanosilylation, characterized by the Si─C bond dissociation of TMSCN as the rate-determining step. [19] In this reac-…”

“…This process is pivotal in cyanosilylation, characterized by the Si─C bond dissociation of TMSCN as the rate‐determining step. [ 19 ] In this reaction, the loss of an electron from TMSCN leads to a decrease in the Si─C bond order, accelerating bond dissociation. While 100‐MOF with a greater number of interpenetrated sections is anticipated to be more catalytically reactive compared to 87‐MOF, its smaller surface area and pore volume restrict substrate access to the catalytically active sites: 87‐ and 100‐MOF have surface areas of 1857 and 1604 m 2 g −1 , respectively.…”

Mechanistic study of homoleptic trisamidolanthanide-catalyzed aldehyde and ketone hydroboration. Chemically non-innocent ligand participation

“…While the use of rare earth catalysts for the hydroboration of C]X bonds has been on the rise, there has been limited mechanistic information which would provide valuable insight into reaction pathways and their potential manipulation in this emerging eld. [45][46][47][48][49] Quantum chemical studies of these catalytic reaction mechanisms would provide a fundamental understanding of the structures and energetics in question, [50][51][52][53][54] and offer a predictive model to accelerate catalyst design while forecasting reaction outcomes and potential deactivation pathways. 55,56 In recent reports from this Laboratory, the rapid and selective hydroboration of aldehydes, ketones, esters, and amides was achieved using homoleptic lanthanide trisamido precatalysts Ln[N(SiMe 3 ) 2 ] 3 (Ln NTMS ) (TMS = SiMe 3 ) and pinacolborane (HBpin) as the reducing agent (Fig.…”

“…While the use of rare earth catalysts for the hydroboration of CX bonds has been on the rise, there has been limited mechanistic information which would provide valuable insight into reaction pathways and their potential manipulation in this emerging field. 45–49 Quantum chemical studies of these catalytic reaction mechanisms would provide a fundamental understanding of the structures and energetics in question, 50–54 and offer a predictive model to accelerate catalyst design while forecasting reaction outcomes and potential deactivation pathways. 55,56…”