Novel 13β- and 13α-d-homo steroids: 17a-carboxamido-d-homoestra-1,3,5(10),17-tetraene derivatives via palladium-catalyzed aminocarbonylations

Add time:08/19/2019    Source:sciencedirect.com

17a-Methoxycarbonyl- and 17a-carboxamido-d-homoestra-1,3,5(10),17-tetraene derivatives were synthesized by palladium-catalyzed carbonylation reactions of the corresponding 17a-iodo-d-homoestra-1,3,5(10),17-tetraene derivatives using methanol and various amines as O- and N-nucleophiles, respectively. Both the natural (13β) and the epi (13α) series of compounds were isolated. The 17a-iodo-17-ene functionalities in the two 13-epimer series differ in reactivity. While the aminocarbonylations were practically complete in the 13β series in reasonable reaction time under mild conditions and high isolated yields were achieved, the corresponding 13α-17a-iodo-17-ene substrate has shown decreased reactivity resulting in moderate to low yields. However, under high carbon monoxide pressure (40 bar) excellent yields can be obtained even in the 13α series. The aminocarbonylation was completely chemoselective in both series, i.e., the corresponding 17a-carboxamido-17-ene derivatives were formed exclusively.

▶ The paper describes the synthesis of 17a-alkoxycarbonyl- and 17a-carboxamido-d-homoestra-1,3,5(10),17-tetraene derivatives via homogeneous carbonylation in the presence of ‘in situ’ formed palladium catalysts. ▶ Although this reaction is known as a powerful synthetic tool for the synthesis of the great variety of model compounds and compounds of practical interest (such as steroids and various heterocycles), its potential for the functionalization of d-homo-steroids has not been shown. ▶ In the present study, compounds belonging both to the 13α- and 13β-series were synthesized via the keton–hydrazon–iodoalkene–carboxamide/ester reaction route. ▶ It has to be emphasized that the reactions are highly chemoselective, therefore are of direct synthetic interest.

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