Reactions of silamorpholinones and acylsilamorpholines with electrophilic reagents. X-ray structure of products including a pentacoordinated silicon compound

Reactions of 2-sila-5-morpholinones, 4-acyl-2-silamorphoiines and 4-acyl-2, 6-disilamorpholines with electrophilic reagents generally lead to the openi ng of the sila- or disilacycle by cleavage of the Si-O bond with subsequent rearrangement to form five-membered chelate derivatives where the amide ox ygen atoms coordinate with the silicon to form pentacoordinate silicon spec ies. Multinuclear NMR spectroscopy and X-ray diffraction studies were used for structural investigation of the products. 4-Acyl-2,6-disilamorpholines initially form adducts with strong acids where the amide oxygen is protonat ed by the acid as demonstrated by X-ray crystallography. (C) 2001 Elsevier Science B.V. All rights reserved.