Activated Michael Acceptors as Precursors to Heterocycles. 1. 2-Azetidinones from 2-(Arylsulfonyl)propenoyl Chlorides and Amines
journal contributionposted on 21.07.1998, 00:00 by Feng Zhou, Jonathan Rosen, Jennifer M. Zebrowski-Young, Patricia M. Freihammer, Michael R. Detty, Rene J. Lachicotte
The addition of NH3 and other primary amines to Z-3-phenyl-2-(arylsulfonyl)propenoyl chlorides gives trans-2-arylsulfonyl-3-phenyl-2-azetidinones as the major product in addition to the corresponding 2-arylsulfonyl-3-phenylpropenamide. Electron-withdrawing substituents in the arylsulfonyl group increased the percentage of products derived from 1,4-addition relative to 1,2-addition, while electron-donating substituents increased the amount of 1,2-addition observed in the product mixture. Addition of α-methylbenzylamine gave a 68:32 mixture of the two diastereomers of the trans-azetidinone. The major diastereomer was identified as the 1-(1R)-(3S,4S) and 1-(1S)-(3R,4R) enantiomers 16a by single-crystal X-ray crystallographic analysis. Phenylthio and phenylsulfoxo substituents did not promote 1,4-addition, although the addition of ammonia to Z-3-phenyl-2-(phenylsulfoxo)propenoyl chloride (7a) gave a 95:5 ratio of the corresponding propenamide 8a and a 3-(phenylsulfoxo)azetidinone 9a. trans-4-Phenyl-3-(arylsulfonyl)-2-azetidinones 12a and 12c were sulfonated by the pyridine−SO3 complex to give the corresponding N-sulfonates 28 in >80% yield. The p-methoxybenzyl substituent of 15 was removed by ceric ammonium nitrate in CH3CN to give 12a in 70% yield.