3,5-bis(trifluoromethyl)phenyl sulfones in the Julia-Kocienski olefination - Application to the synthesis of tri- and tetrasubstituted olefins

摘要

3,5-Bis(trifluoromethyl)phenyl (BTFP) sulfones 8a-d are successfully employed in the modified Julia olefination reaction with carbonyl compounds employing phosphazene base P4-tBu at room temp. in THF, affording tri- and tetrasubstituted olefins in good yields. The Julia-Kocienski olefination between primary alkyl BTFP sulfones 8a,b and aromatic and aliphatic ketones affords the corresponding trisubstituted alkenes in good yields and low stereoselectivities. On the other hand, higher yields and stereoselectivities are obtained in the synthesis of trisubstituted olefins through the other approach, the coupling of secondary alkyl BTFP sulfones 8c,d with aliphatic, aromatic and alpha,beta-unsaturated aldehydes. For the first time, tetrasubstituted olefins are synthesized by means of the Julia-Kocienski protocol when the isopropyl BTFP sulfone 8c reacts with aliphatic and aromatic ketones, employing P4-tBu as base at THF reflux. ((c) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006).