Synthesis and structure of novel Si-substituted silylpropyl derivatives of 2-mercaptobenzoxazole and 2-mercaptobenzothiazole

A previously unknown carbofunctional (trimethoxysilyl)propyl derivative of the 2-mercaptobenzoxazole, C6H4NOCS(CH2)3Si(OMe)3, containing a tetracoordinated silicon atom was synthesized by nucleophilic substitution of the chlorine atom in the (3-chloropropyl)-trimethoxysilane with the benzoxazol-2-ylsulfanyl group. The reaction of 2-[(trimethoxysilyl)propylsulfanyl]benzoxazole or –benzothiazole with boron trifluoride etherate led to a previously unknown hydrolytically unstable Si-fluoropropyl derivatives of 2-mercaptobenzoxazole or 2-mercaptobenzothiazole, C6H4N(Y)CS(CH2)3SiF3 (Y = O, S). By transesterification of 2-[(trimethoxysilyl)-propylsulfanyl]benzoxazole by tris(2-hydroxyethyl)amine, a new silatranylpropyl derivative of 2-mercaptobenzoxazole containing an intramolecular coordination bond N→Si and a pentacoordinated silicon atom, C6H4NOCS(CH2)3Si(OCH2CH2)3N, was obtained.