Palladium-catalysed intramolecular enolate O-arylation and thio-enolate S-arylation: synthesis of benzo[b]furans and benzo[b]thiophenes
摘要:
Enolates derived from alpha-(ortho-haloaryl)-substituted ketones undergo palladium-catalysed C-O bond formation to deliver benzofuran products in good yield. A catalyst generated from Pd-2(dba)(3) and the ligand DPEphos effects the key bond formation to deliver a variety of substituted products from both cyclic and acyclic precursors. The analogous thio-ketones undergo C-S bond formation using identical reaction conditions and are converted to benzothiophene products. A cascade sequence that produces the required a-aryl ketones in situ has also been developed, although the substrate scope is more restricted. (c) 2006 Elsevier Ltd. All rights reserved.