Multicomponent Queuing Cascades of Bicyclopropylidene, Carbon Monoxide and Aryl Iodides or Aryl Thiols

Abstract

Bicyclopropylidene (1) reacts with N-(2-iodophenyl)-4-methylbenzenesulfonamide (2-NTs) and carbon monoxide (2−3 bar) under mild conditions in a novel palladium-catalysed tetramolecular cascade to give the dispiro compound 3-NTs (61%). The structure of 3-NTs was determined by X-ray analysis. With ortho-iodophenol (2-OH) replacing 2-NTs a mixture of 3-O (20%) and 3,4-dihydro-2H,5H-pyrano[3,2-c]chromen-2-one (4-O; 11%) was obtained. Mechanistically this cascade is interpreted in terms of the acylation of 1 followed by a cyclopropylcarbinyl-homoallyl rearrangement, carbon monoxide insertion and intramolecular trapping of a nucleophile. Various thiophenols reacted with 1 and CO (2−3 bar) to give the thiocarbonylated products 14a−d,g and 15a−c,g (33−77% yield). With ortho- or para-halo-substituted thiophenols as substrates the vinyl lactones 16e−h (31−55% yield) were obtained in a novel palladium-catalysed five-component cascade. The outcome of this cascade is discussed in terms of the electronic and steric properties of the thiophenols. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)