Synthesis and structural features of indium(iii) furan-2-thiocarboxylates showing efficient catalytic activity toward multicomponent reactions via Knoevenagel condensation

Abstract

A series of furan-2-thiocarboxylate complexes of indium(III), Et₃NH[In(SCOf)₄] (1), ⁱPr₂NH₂[In(SCOf)₄] (2), [In(2,2′-bipy)(SCOf)₃] (3a), and [In(1,10-phen)(SCOf)₃] (3b), have been synthesized and structurally characterized. Complex 4, [In(TMEDA)(SCOf)(SH)₂], was obtained by the partial hydrolysis of [In(TMEDA)(SCOf)₃] (3). Heterobimetallic complexes [(SCOf)₂In(μ-SCOf)₂Cu(PPh₃)₂] (5) and [(SCOf)₂In(μ-SCOf)₂Ag(PPh₃)₂] (6), were also synthesized and characterized. In an attempt to synthesize the binary compound, In(SCOf)₃ (7), a thioester fCOSCH₂SCOf (8) was obtained serendipitously; thus, a novel convenient approach for thioester synthesis is introduced. The catalytic activities of all the complexes were assessed for Knoevenagel condensation and Knoevenagel initiated MCRs for the synthesis of chromene and imidazopyrimidine derivatives and it was found that complex 2 is a very efficient catalyst (much superior to the previously reported ones).