Synthesis of oxazoles from O-trimethylsilyl acyltrimethylsilane cyanohydrins
摘要:
Sequential addition of organolithium reagents and acyl chlorides (or anhydrides) to O-trimethylsilyl acyltrimethylsilane cyanohydrins affords beta-(acyloxy)-N,N-bis(trimethylsilyl) enamines which cyclize to substituted oxazoles under thermolysis or treatment with trimethylsilyl trifluoromethanesulfonate. Oxazoles were prepared containing alkyl and phenyl substituents at C-5, alkyl, alkenyl, and phenyl substituents at C-4, and alkyl, alkenyl, phenyl, and functionalized substituents at C-2.
The metalation-silylation of O-trimethylsilyl aldehyde cyanohydrins
摘要:
The metalation-trimethylsilyation of O-trimethylsilyl (saturated) aldehyde cyanohydrins was achieved by in situ treatment with LDA and trimethylchlorosilane at -78-degrees-C. C-Silyl products (O-trimethylsilyl acylsilane cyanohydrins) generally predominated, but N-silyl derivatives (ketenimines) were found in some instances. LDA could be added across the C = N bond of the latter. The metalation-trimethylsilylation of O-trimethylsilyl benzaldehyde cyanohydrin could only be effected if 2 equiv of trimethylchlorosilane were employed per equivalent of cyanohydrin anion.