Palladium-catalysed aminocarbonylation of steroidal 17-iodo-androst-16-ene derivatives in N,N′-dialkyl-imidazolium-type ionic liquids

Abstract

The use of [bmim]⁺[BF₄]⁻, [bmim]⁺[PF₆]⁻ and [emim]⁺[PF₆]⁻ ionic liquids as solvents in homogeneous catalytic aminocarbonylation of 17-iodo-5α-androst-16-ene at atmospheric carbon monoxide pressure has been investigated. It has been proved that after the extraction of the product with toluene, the ionic liquid–catalyst mixture could be recycled several times. Although there was a loss of catalytic activity in the further cycles, even 94% conversion can be achieved after the fifth run by using [bmim]⁺[BF₄]⁻ ionic liquid. The conversion depended strongly both on the properties of the ionic liquid and those of the catalyst. The activities of the in situ palladium(0) catalysts prepared from Pd(OAc)₂ and various phosphine ligands (PPh₃, TPPTS, DPPBA) have been compared. The method can be effectively used for the aminocarbonylation of other steroids with 17-iodo-16-ene functionality.