Pyrolysis of 17-oxygenated 16-methylene-20-oxosteroids. Part I. Formation of 2′-methylandrostano[17,16-c]furans

Abstract

16-Methylene-17α-acetoxyprogesterone (1b) was pyrolysed above 300° to yield 2′-methyloxo-4-androsteno-[17,16-c]furan (3) and 16-acetoxymethyl-16-dehydroprogesterone (5). Pyrolysis of (5) at 360° gave (3). The 16-methylene-17-acetoxy-20-ketosteroids (10c), (2b), (12), (16), and (21) were pyrolysed to the corresponding furanoid compounds (9), (4), (13), (17), and (22) as well as to the allylic rearrangement products (11), (7a), (14a), (18a), and (23), respectively. Pyrolysis of (19) gave only (20). The furan (3) was reactive in Diels–Alder additions and was converted thereby into the benzenoid structures (26) and (28a).