Chiral oxazaborolidinium ion

Cyanosilylation of methyl ketones has been carried out using diphenylmethylphos-phine oxide and trimethylsilyl cyanide, generating a phosphorus isonitrile-type species, Ph2MeP(OTMS)(N=C ), as the reactive intermediate.271 A chiral oxazaborolidinium ion catalyst renders the reaction enantioselective. 

Chiral oxazaborolidinium ion is an excellent catalyst for the cyanosilylation of methyl ketones promoted by cyanotrimethylsilane and diphenylmethyl phosphine oxide (eq 27). Chiral thiourea (eq 28) and amino acid salt (eq 29) have been developed and employed as catalysts in the enantioselective s)m-thesis of cyanohydrins and their derivatives. 

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