Iron-catalyzed unexpected easy access to stereodefined trimethylsilyl vinyl ketenes.

Stereodefined trimethylsilyl vinyl ketenes with polysubstitution have been synthesized highly regio- and stereoselectively via an iron-catalyzed reaction of 2-trimethylsilyl-2,3-allenoates with Grignard reagents in good to excellent yields. The reaction was believed to proceed via a conjugate addition and elimination mechanism. Applications of the products for the synthesis of stereodefined α-silyl-β,γ-unsaturated enones, a stereodefined triene, and polysubstituted phenols have been carefully demonstrated.