A NOVEL REACTION AND MECHANISM OF A DIHALOGENATED Δ4-3-KETOSTEROID: STEREOELECTRONIC CONTROL IN A COMPLICATED SN2′ DISPLACEMENT

Stereochemistry of the acetolysis of 4,6β-dibromo-Δ4-3-ketosteroicl was examined and a new route of simultaneous introduction of two O-functions at C-2 and C-6 on the steroid skeleton has been established. The reaction is interpreted to proceed by characteristic and successive SN2′ reaction mechanisms, and stereoelectronic effects control the stereochemistry of the reaction. There is no occurrence of SN1, SN2, and any rearrangement courses.