Diels-Alder reaction of (2,4,6-trialkylphenyl)phospholes with N-phenylmaleimide

2,4,6-Trialkylphenylphospholes 3a (R = Me), 3b (R = i-Pr) and 3c (R = t-Bu) , with increasing flattening at phosphorus and hence with increasing electr on delocalisation, underwent the Diels-Alder reaction with N-phenylmaleimid e to give predominantly cycloadducts 4a-c with the trialkylphenyl substitue nts anti to the phosphanorbornene double bond. With increasing aromaticity, the cycloaddition was slower The stereostructure of the products (6 and 7) obtained after oxidation was confirmed by stereospecific (2)J(PC) NMR coup lings and by an independent synthesis. (C) 2000 John Wiley & Sons, Inc.