Azasteroids. Synthesis by Diels-Alder Reaction between Maleimides, Citraconimide, and Triazolindiones and 1-(1-Trialkylsiloxyvinyl)-3,4-dihydronaphthalene Derivatives

18-Nor-16-azaestrane derivatives with 8β, 13β, and 14β orientation were isolated from Diels-Alder reactions between maleimides or citraconimide and 1-(1-siloxyvinyl)naphthalene derivatives. (8RS)-13,14,16-Triazaestrane derivatives were synthesized from 1,2,4-triazolin-3,5-diones. The parent 11-oxo derivatives were obtained by desilylation, and they were transformed into 11-hydroxyimino derivatives. 3-Hydroxy derivatives, finally were synthesized by cleavage of the 3-methoxy group with BBr3. During these transformations the stereochemistry of the steroidal skeleton was not changed. The stereochemistry of these “unnatural” steroids was elucidated by spectroscopic methods, and compared with results from calculations, and with the configuration of natural estrane derivatives. Finally, an improved method for the synthesis of the starting material, 6-methoxy-1-[(1-trialkylsiloxy)-vinyl]-3,4-dihydronaphthalene was developed.