One-pot tandem hiyama alkynylation/cyclizations by palladium(II) acyclic diaminocarbene (ADC) complexes yielding biologically relevant benzofuran scaffolds

Abstract

A series of palladium acyclic diaminocarbene (ADC) complexes of the type cis-[(R1NH)(R2)methylidene]- PdCl2(CNR1) [R1 = 2, 4, 6-(CH3)3C6H2: R2 = NC5 H10 (2); NC4H8 (3); NC4H8O (4)] were used not only to perform the Csp2-Csp Hiyama coupling between aryl iodide and triethoxysilylalkynes but also to subsequently carry out the one-pot tandem Hiyama alkynylation/cyclization reaction between 2- iodophenol and triethoxysilylalkynes, giving a convenient timeefficient access to the biologically relevant benzofuran compounds. The palladium ADC complexes (2-4) were conveniently synthesized by the nucleophilic addition of secondary amines, namely, piperidine, pyrrolidine, and morpholine on the cis-{(2, 4, 6-(CH3)3C6H2)NC}2PdCl2 in moderate yields (ca. 61-66%) .