SOLVOLYSIS OF TRICYCLO[3.1.0.02,6]HEX-3-YL AND BICYCLO[2.1.1]HEX-2-YL SULFONATES

Solvolyses of cis-tricyclo[3.1.0.0(2,6)]hex-3,4-diyl ditosylate (12) and cis-bicyclo[2.1.1]hex-2,3-diyl ditosylate (27) have been carried out in 80% aqueous ethanol in the presence of ethyldiisopropylamine. In the former case, endo,endo-tricyclo[2.2.0.0(2,6)]hexane-3,5-diol (13a), its monoether 13b and diether 13c were products whereas in the latter the monoethers 28b, d, e, g and the diethers 28a, c, f of bicyclo[3.1.0]hexane were formed. In pure ethanol, 12 was converted into pure 13c in good yield. In the presence of the weaker base 2,6-lutidine, the solvolysis of 12 in aqueous ethanol gave different products, i.e. exo,exo-4,6-diethoxybicyclo[3.1.0]hex-2-ene (14a) and several aldehydes, inter alia cyclopentadiene-1-carboxaldehyde (15). In control experiments, the tricyclic compounds 13b, c were converted into 14a, 15 and further aldehydes as well as into the bicyclo[2.1.1]hexene derivatives 19a, b. Sulfonates of tricyclo[3.1.0.0(2,6)]hexan-3-ol (21a) could not be isolated but its mesylate 21c was characterized by NMR spectroscopy and hydrolysed in aqueous acetone to give tricyclo[2.2.0.0(2,6)]hexanendo-3-ol (22a). It is concluded from these results that the dissociations of the above sulfonates do not lead to unrearranged carbocations. Rather, they proceed with participation of the beta-carbon in trans position relative to the leaving group resulting in the immediate generation of rearranged cations. - Kinetic studies show that the tricyclic mesylate 21c solvolyses in 80% ethanol/water 1.4 . 10(5) times as fast as bicyclo[2.1.1]hex-2-yl tosylate (25), and the tricyclic ditosylate 12 solvolyses 6 . 10(5) as fast as the corresponding bicyclic ditosylate 27. These rate enhancements are similar to those previously observed for less strained cyclopropylcarbinyl substrates.