EFFECT OF INCREASING ELECTRON DEMAND UPON THE PRODUCT-DETERMINING TRANSITION-STATE IN THE REACTION OF 4-SUBSTITUTED 2-NITROBENZENESULFENYL CHLORIDES AND BENZENESULFENYL CHLORIDES WITH BICYCLO[2.2.1]HEPTA-2,5-DIENE

The effect of increasing electron demand upon the product-determining transition state in the reaction of arenesulfenyl chlorides with bicyclo[2.2.1]hepta-2, 5-diene has been investigated. As the electron-donating ability of the remote substituents on the phenyl ring of the sulfenyl chloride is varied from nitro to methoxy, the relative proportion of nortricyclene adduct is found to decrease relative to that of simple exo-anti addition. An ortho nitro group was found to lead to a stabilizing interaction only in the case of 2, 4-dinitrobenzenesulfenyl chloride. A mechanism involving the competition of three neighboring-group effects is suggested, wherein the neighboring groups are respectively the 5, 6 double bond of the substrate, the sulfur atom from the electrophile, and the ortho nitro substituent. In the first two cases the competition is with respect to the stabilization of positive charge at C-2. In the latter case the ortho nitro group is able to stabilize charge development on sulfur while the sulfur atom is itself acting as a neighboring group. © 1979, American Chemical Society. All rights reserved.