CHEMICAL CONSEQUENCES OF LONG-RANGE ORBITAL INTERACTIONS IN NORBORNANE-1,4-DIOL MONOSULFONATE ESTERS

Seven monotosylated 1,4-diols with the rigid norbornane skeleton were treated with a strong base in refluxing benzene to find out whether these compounds react by initial heterolysis of the tosylate ester bond induced by long-range orbital interactions. The tosylates 1-7 were designed to investigate the influence of the sigma-relay (U-, sickle-, or W-shaped) between the donor and acceptor end of the system, to check whether primary carbocationic ion pairs could act as intermediates, and to study conformational influences on reactivity and product formation. Tosylate 1 with a U-like arrangement of the sigma-relay reacted relatively slowly and followed reaction pathways in which no long-range orbital interactions are involved. The reaction outcome of tosylate 2 which possesses a sickle-like arrangement of the sigma-relay indicates two competitive processes with and without the involvement of long-range orbital interactions. The secondary tosylates 3, 6, and 7 which all possess a W-like arrangement reacted relatively fast and showed predominantly homofragmentation. Although an ideal W-like arrangement is present in the primary tosylates 4 and 5, no reactions in which long-range orbital interactions are involved were observed. The tosylates 6 and 7 in which the tosylate group is conformationally mobile can give rise to mixtures of products. The ratio in which these products are formed can be rationalized by using the Curtin-Hammett principle.