Preparation and reactions of steroidal cross-conjugated 3-nitrones

Abstract

Treatment of the N-methylnitrone (1b) of dichlorisone acetate (E–Z-mixture) with toluene-p-sulphonyl chloride in pyridine in the presence of water gave dichlorisone acetate (1a)(88%). In the presence of hydrogen sulphide, however, the nitrone was deoxygenated to give the corresponding imine (1c), which on prolonged reaction with hydrogen sulphide in pyridine afforded the corresponding 1,4-diene-3-thione (1d). Similarly prepared were the unstable imines (2d), (3c), and (4c), which were smoothly converted into the corresponding thiones (2e), (3d), and (4d), respectively. In the absence of strong nucleophiles, dichlorisone acetate nitrone (1b) was treated with toluene-p-sulphonyl chloride in pyridine to give the corresponding trienimine (1g)(45%). Under similar conditions, however, prednisolone-21-propionate nitrone (3b) gave the 2-p-tolylsulphonyloxy-derivative (3e) as the major product. Separate treatment of both Z- and E-isomers of dehydrotestosterone acetate nitrone [(2b) and (2c)] afforded, in both cases, the 2-p-tolylsulphonyloxy-derivative (2g)(25%), whereas betamethasone nitrone (4b) gave a mixture of the 2-p-tolylsulphonyloxy-dienimine (4f) and the trienimine (4h) in low yield.