[reaction: see text] A study of the effect of Michael acceptor stereochemistry on the efficiency of intramolecular Morita-Baylis-Hillman (MBH) reactions has been performed. The reactions were catalyzed by a phosphine, and the reaction substrates studied were enones containing a pendant aldehyde moiety attached at the beta-position of the alkene group. In all cases examined with PPh3 as the catalyst, cyclization substrates possessing (Z)-alkene stereochemistry afforded a much higher yield of the desired product than did the E isomeric substrates under identical reaction conditions. This was also true when a polymer-supported phosphine catalyst was used. While both alkene isomers afforded the same product, in parallel reactions, the Z isomer afforded 2.5-8.5 times higher yield than did the corresponding E isomer. It is proposed that steric effects are a possible source of this dramatic difference in reactivity. Substrates where the beta-substituent is cis to the electron-withdrawing substituent are relatively more accessible to react with the nucleophile catalyst than are their trans counterparts. These findings are expected to be useful in the design of synthetic intermediates, as intramolecular MBH reactions are being increasingly used in the preparation of complex synthetic targets.

In the aza-Morita-Baylis À Hillman reaction of N-sulfonated imines (N-arylmethylidene-4-methylbenzenesulfonamides and others) with methyl vinyl ketone (MVK), we found that in the presence of a catalytic amount of the chiral phosphine Lewis bases (R)-(À)-6,6'-bis [tris(3,3,4,4,5,5,6,6,7,7,8,8,8- 6'-(3,3,4,4,5, 5,6,6,7,7,8,8,8-tridecafluorooctyl) -2'-(diphenylphosphanyl)-[1,1']binaphthalenyl-2-ol LB3 bearing two perfluoroalkane chains at 6,6'-positions of the naphthalene framework, the corresponding adducts could be obtained in good yields with good to high ee (52 -95% ee) at room temperature (15 8C) or low temperature ( À 20 8C) in THF, respectively. LB3 is more effective in this reaction than the previously reported original chiral phosphine Lewis base (R)-(À)-2'-diphenylphosphanyl-[1,1']binaphthalenyl-2-ol LB1.

Cyclopentane derivatives Q 0030Influence of Michael Acceptor Stereochemistry on Intramolecular Morita-Baylis-Hillman Reactions. -The configuration of the starting enones has a strong effect on their reactivity. Under identical conditions, the (Z)-isomers are much more reactive. -(TENG, W.-D.; HUANG, R.; KWONG, C. K.-W.; SHI, M.; TOY*, P. H.; J. Org.