Palladium-catalyzed synthesis of 4-sila-4H-benzo[d][1,3]oxazines by intramolecular Hiyama coupling.

ABSTRACT

A palladium-catalyzed synthesis of 4-sila-4H-benzo[d][1,3]oxazines, silicon-switched analogs of biologically relevant 4H-benzo[d][1,3]oxazines, was developed by the intramolecular Hiyama coupling of 3-amido-2-(arylsilyl)aryl triflates. The present reaction is an unusual way of utilizing the Hiyama coupling, enabling the synthesis of value-added organosilanes as the main products. The intramolecular nature of transmetalation with inversion of the stereochemistry at the silicon center was revealed by the mechanistic investigation, and an asymmetric variant of this process was also demonstrated to give silicon-stereogenic 4-sila-4H-benzo[d][1,3]oxazines with relatively high enantioselectivity.