ORGANOFLUOROSILICATES IN ORGANIC SYNTHESIS. XV. REACTION OF exo- AND endo-5-NORBORNEN-2-YLSILYL DERIVATIVES WITH N-BROMOSUCCINIMIDE. DIFFERENCE IN REACTIVITY BETWEEN HEXACOORDINATE AND TETRACOORDINATE SILICON COMPOUNDS

Article abstract of DOI:10.1016/S0022-328X(00)86818-7

The reactions of potassium 5-norbornen-2-ylpentafluorosilicate (I) and 5-norbornen-2-yltrimethylsilane (II) with NBS were examined.The former reaction gave 3-nortricyclyl bromide (IV) as the only detectable product, arising from the carbon-silicon bond cleavage.The latter reaction, however, gave 3-bromo-1-nortricyclytrimethylsilane (V) as the major product, resulting from cleavage of the carbon-hydrogen bond α to silicon, together with IV and and unidentified product.GLC-monitoring of the reactions showed the higher reactivity of the norbornenyl derivative having the leaving group in the endo position irrespective of whether the leaving group is SiF5 or H.Since no inhibition was observed by the addition of hydroquinone in the dark, the reactions have been regarded as homoallylic electrophilic substitutions.A concerted mechanism seems to be consistent with the experimental data.Cleavage of 1-notricyclytrimethylsilane by iodine monochloride to give 1-iodonortricyclene has also been studied.