NHC catalysed trimethylsilylation of terminal alkynes and indoles with Ruppert's reagent under solvent free conditions

Abstract

A highly efficient organo-catalytic protocol for the trimethylsilylation of terminal alkynes and N-silylation of indoles employing Ruppert's reagent as a trimethylsilyl source have been developed under solvent and fluoride free conditions.

Silicon–Nitrogen Bond Formation via Heterodehydrocoupling and Catalytic N‐Silylation

“…N-heterocyclic carbenes and NaH catalyzed the N-silylation of indoles and pyrrole with Ruppert's reagent at ambient temperature (Scheme 4). [34] The ubiquitous Lewis acid catalyst, B(C 6 F 5 ) 3 ,a ppearsi na report by Paradies in whichP h 2 MeSiH was dehydrocoupled with av ariety of primary and secondary substrates such as anilines, diamines, diarylamines, andi ndoles. [35] Wright and co-workers used Al(NEt 2 ) 3 for coupling primary amines with PhSiH 3 at 70 8C, achieving conversionso f3 3-94 %, yet with limited product selectivity.…”

“…N ‐heterocyclic carbenes and NaH catalyzed the N‐silylation of indoles and pyrrole with Ruppert's reagent at ambient temperature (Scheme 4). [34] …”

“…[33] Scheme4.N-silylation of substituted indolesw ith Ruppert's reagent. [34] Scheme5.Proposed catalytic cycle for the N-silylation of Ph 2 MeSiH with 2,3dimethylindole catalyzed by B(C 6 F 5 ) 3 . [35] Scheme6.Mechanism for the dual heterodehydrocoupling and olefin hydrogenation reported by Stephan and co-workers.…”

Highly Chemoselective DMPU‐Mediated Trialkylsilylation of Terminal Alkynes Using Trifluoromethyltrialkylsilane

“…Other methods mediated by Zn or catalyzed by transition metals such as Ru and Ir have been developed; thus, this reaction can be applied to substrates containing ketones or esters. As another approach, the silylations of terminal alkynes using trifluoromethyltrimethylsilane with a catalyst such as KF/CsF, TBAF, or an N ‐heterocyclic carbene have recently been reported. Trifluoromethyltrimethylsilane (CF 3 SiMe 3 , now known as the “Ruppert–Prakash reagent”) has normally been used as a reagent for the trifluoromethylation of aldehydes, ketones, imines, hydrazones, and aziridines.…”

N-Heterocyclic Carbene Catalyzed 1,6-Conjugate Addition of Me3Si-CN to para-Quinone Methides and Fuchsones: Access to α-Arylated Nitriles

“…In fact, only one example is reported for the 1,6-conjugate addition HCN to puupehenone, which is a dienone system . In our continuing program on the development of NHC catalyzed transformations, we sought to employ the NHC catalyzed silicon activation concept for the synthesis of α-arylated nitriles through 1,6-conjugate addition of Me 3 Si-CN to para -quinone methides ( p -QMs) [Figure ]. While the chemistry of p -QMs has been investigated by many research groups including our group, this particular NHC catalyzed vinylogous conjugate cyanation reaction of p -QMs using Me 3 Si-CN as a cyanide source has not been examined to date, which prompted us to investigate this transformation in a detailed manner.…”