Convenient preparation of A-ring fused pyridines from steroidal enamides

A facile strategy for the preparation of A-ring fused pyridosteroids has been accomplished in high yields by the reaction of Vilsmeier reagent (chloromethyleneiminium salt) with steroidal A-ring enamides (2- and 3-ene) under thermal conditions. The structure of 6′-chloro-5α-cholest [3,2-b]pyridine was determined by X-ray analysis.