Palladium-catalyzed hydroarylation, hydroalkenylation, and hydrobenzylation of ynol ethers with organohalides: A regio- and stereoselective entry to α,ß- and ß,ß-disubstituted alkenyl ethers.

A Pd-catalyzed reductive addition of organohalides, including aryl, alkenyl, and benzyl halides, to ynol ethers has been realized in the presence of 2-propanol, giving α,ß- and ß,ß-disubstituted olefinic ethers in satisfactory yields with excellent regio- and stereoselectivity. It represents the first highly regio- and stereoselective hydroarylation, hydroalkenylation, and hydrobenzylation of ynol ethers.

An operationally simple approach to (E)-α-halo vinyl sulfides and their applications for accessing stereodefined trisubstituted alkenes.

An operationally simple and practical protocol for the synthesis of (E)-α-halo vinyl sulfides has been achieved via a highly regio- and stereoselective hydrohalogenation of alkynyl thioethers using lithium halides in HOAc or propionic acid at room temperature. It permits the formation of (E)-α-chloro and (E)-α-bromo vinyl sulfides in satisfactory yields with good to excellent stereoselectivities. Moreover, this work results in a new method for the assembly of stereodefined (E)- or (Z)-trisubstituted alkenes featuring the first coupling of the C-X bond of (E)-α-halo vinyl sulfides followed by a subsequent Ni-catalyzed coupling of the C-S bond with Grignard reagents.

Highly stereoselective synthesis of (Z)-1,2-dihaloalkenes by a Pd-catalyzed hydrohalogenation of alkynyl halides.

An unprecedented Pd-catalyzed hydrohalogenation of alkynyl halides for the regio- and stereoselective synthesis of (Z)-1,2-dihaloalkenes has been realized using [(allyl)PdCl](2) as the catalyst and cis,cis-1,5-cyclooctadiene as the ligand. The advantages of this protocol are well illustrated by the assembly of trisubstituted (Z)-enynes and multifunctional benzenes via iterative cross-coupling reactions or tandem Diels-Alder-aromatization reactions, respectively.

Synthesis of cis-1,2-dihaloalkenes featuring palladium-catalyzed coupling of haloalkynes and α,ß-unsaturated carbonyls.

A highly regio- and stereoselective method for the synthesis of cis-1,2-dihaloalkenes through Pd-catalyzed coupling of haloalkynes and α,ß-unsaturated carbonyls has been reported. Excellent stereoselectivities (Z/E up to >98:2) were observed in most cases. This method was subsequently applied to synthesize the functionalized conjugated enyne via the mono-Sonogashira coupling reaction of cis-1-chloro-2-iodoalkene.