4+3 cycloaddition reactions of halogen-substituted cyclohexenyl oxyallyliccations

2,6-Dibromo- and 2,2-dichlorocyclohexanone react with base in the presence of various dienes to give 4+3 cycloadducts in fair to good yields. Prelimin ary studies of the cycloadducts suggest that they are unstable and are reca lcitrant to nucleophilic addition and cross-metathesis. However, the LAH re duction products undergo a quasi-Favorskii rearrangement upon treatment wit h potassium hydride and one cycloadduct derivative was dehalogenated using radical chemistry. (C) 1999 Elsevier Science Ltd. All rights reserved.