New steroidal heterocycles: synthesis and structure of androst-2-eno[2,3-g](tetrazolo[1,5-a]pyridimines), androst-4-eno[3,2-f](tetrazolo[1,5-a]pyrimidine), and androstano[17,16-f](tetrazolo[1,5-a]pyrimidines)

Abstract

The condensation of 5-aminotetrazole (1) with 2-hydroxymethylene-3-oxosteroids [(2)–(5) and (16)] gave steroid-2-eno[2,3-g](tetrazolo[1,5-a]pyrimidines)[(7)–(10) and (17)]. However, the reaction of a 2-hydroxymethylene-Δ⁴-3-oxosteroid (18) with 5-aminotetrazole (1) gave a product which exists predominantly in the form (19a) in which the tetrazolopyrimidine system is linearly fused to the steroid nucleus. During the acetylation of (19a) with acetic anhydride–pyridine, in addition to the expected 17β-acetoxy-derivative (21a), 17β-acetoxy-4-oxo-5ξ-androst-2-eno[2,3-g](tetrazolo[1,5-a]pyrimidine)(22a) was isolated. The reaction of 16- hydroxymethylene-17-oxosteroids (26) and (29) with 5-aminotetrazole (1) also gave the linearly fused tetrazolopyrimidines (27) and (30). All the tetrazolopyrimidines exist in the tetrazolo-form in dimethyl sulphoxide solution and in the solid state, whereas in bromoform and deuteriochloroform solutions the tetrazolo-isomers are found to be in equilibrium with small quantities of their corresponding azido-forms. The structures of all these products are elucidated with the help of u.v., i.r., ¹H n.m.r., and ¹³C n.m.r. spectroscopy.