gamma-functionalisation of the 1-phosphanorbornadiene structure

3-Methyl-substituted 1-phosphanorbornadiene oxides or sulfides such as la,b are either metalated by a strong base (n-BuLi or LDA) or brominated by NBS at the methyl substituent. The reaction of the resulting delocalised carba nions 2a,b takes place either at C-2 (H+, Mel) or at the methylene group (M e3SiCl, ClPPh2, I-2) In the last case, gamma-functional (5a,b or 6a,b) or b ridged (7) phosphanorbornadienes are obtained. Similarly, the reaction of 3 -bromomethyl-1-phosphanorbornadiene oxides such as 8 with nucleophiles [NaC H(CO2Me)(2), PhO-, Me2NH, PhCH2NH2] yields the corresponding gamma-function al phosphanorbornadienes 9-12. This chemistry has also been applied to the BIPNOR dioxide 13.