Reduction of aromatic steroidal A rings by lithium in ethyl amine

The reduction of 3-methoxy-estra-1,3,5(10)-trien-17β-ol (6) and 13-ethyl-3-ethoxy-gona-1,3,5(10)-triene-11α,17β-diol (2) by lithium in ethyl amine in the absence of a proton source is described. Both reductions, contrary to the reports of previous investigators, which indicated the 4-ene to be the main reaction product, gave a complex mixture of products. In the case of the reduction of 2, which is an intermediate in the synthesis of the progestagen desogestrel (1), we obtained the expected known 13-ethyl-gona-4-ene-11α,17β-diol (4) in small amounts and three new steroidal monoenes, 13-ethyl-gona-5(10)-ene-11α,17β-diol (11), 13-ethyl-gona-5(6)-ene-11α,17β-diol (12), and 13-ethyl-gona-1(10)-ene-11α,17β-diol (13). These compounds were characterized as the 11,17-diacetates with the 5(10)-ene 11 being the major compound.