| Abstract
| - The levels of diastereoselection attainable by addition of vinylmagnesium bromide to a selection of bicyclo[2.2.2]octenone derivatives 1−6 in the presence of various Lewis acids such as LiBr, CeCl3, TiCl4, ZnBr2,MgBr2, and Et2AlCl have been determined. The 1,2-addition of ketone 1 with vinylmagnesium bromidein THF provided a mixture of anti- and syn-isomers. The reactions of 2 with vinylmagnesium bromideat room temperature afforded anti- and syn-isomers with preference to anti-isomers in most cases. Thesereactions in the presence of Lewis acids afforded anti-isomers as the major product with an excellentstereoselectivity or as single isomers in some cases. The ketones 3 gave surprisingly different resultsproviding anti-isomers predominantly even in the presence of Lewis acids. The bicyclic ketones 4 and5 and all-carbon tricyclic ketone 6 furnished the syn-isomer as the main product. There is no significanteffect of Lewis acid catalysis in the nucleophilic addition reactions of 1, 4, 5, and 6. The use of a preformedvinylmagnesium bromide−CeCl3 reagent for the addition reactions of 2d−f and 3d−f provided almostexclusively syn-isomers. The substituents and reaction conditions can influence facial selectivity in thenucleophilic additions to the bicyclo[2.2.2]oct-5-en-2-one derivatives.
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