A mild and efficient degradation of ring A of steroids
Abstract
17β-Acetoxy-4,5-secoandrost-3-yn-5-one and 4,5-secopregn-3-yne-5,20-dione, readily available by Eschenmoser-Tanabe fragmentation, have been rearranged to the corresponding 2-ynes, which were then cleaved to afford 2,5-seco-3,4-dinor-derivatives in excellent overall yield. The release of toluene-p-sulphinic acid during the fragmentation step can lead to the acetylation sulphinylation of an extraneous hydroxy-group. The active sulphinylating species is evidently p-tolyl toluene-p-sulphinyl sulphone.