Attempts to determine the stereochemistry of electrophilic addition of acetone to two configurationally rigid Grignard reagents [2-norbornylmagnesium bromide (3) and 3,3-dimethyl-2-norbornylmagnesium bromide (9)] are described. Evidence is presented which suggests that the reaction of 9 with benzophenone proceeds via an electrontransfer pathway. In addition, results describing an improved synthesis of camphenilone and the stereospecific synthesis of exo-2-bromo-3,3-dimethylnorbornane are presented.Despite its long-standing synthetic importance, a detailed understanding of the reaction of Grignard reagents with carbonyl compounds has only recently begun to emerge.2'3 The products of such reactions indicate that several, frequently competitive reaction pathways are available: (a) direct 1,2addition, (b) electron transfer, (c) reduction (when a ß hydrogen is present in the Grignard reagent), and (d) enolization