SYNTHESIS AND ACETOLYSIS OF EPIMERIC 7-TOSYLOXYNORBORNAN-2-ONES

anti-7-Hydroxynorbornan-2-one p-toluenesulfonate (3) and syn-7-hydroxynorbornan-2-one p-toluene-sulfonate (4) have each been prepared via two alternate synthetic routes. Solvolysis of these epimeric tosylates showed that 3 underwent acetolysis more than 104 times faster than 4 (at 200˚). Comparison of the rate of acetolysis of 3 to that of 7-tosyloxynorbornane showed a relative rate difference of 2 X 107 at 25 ˚. The acetolysis of 3 gave anti-7-acetoxynorbornan-2-one as the only product, while both syn-7-acetoxynorbornan-2-one and anti-7-acetoxynorbornan-2-one were obtained in the acetolysis of 4. These observations are consistent with the acetolysis of 3 occurring via the formation of the enol of 3 followed by solvolysis of this enol with neighboring group participation of the π electrons of the enol double bond. This theory was demonstrated to be correct through the solvolysis of 3 in acetic acid-O-d where deuterium incorporation during the enol-keto tautomerism placed a deuterium α to the carbonyl. Since enol formation was part of the overall rate-determining scheme, an increasing deuterium isotope effect was noted as the reaction proceeded (as the amount of α-deuterium increased). This rate decrease due to the incorporation of deuterium required that the enol be involved as the solvolyzing intermediate. These observations established a new route for neighboring group participation of the carbonyl function. © 1969, American Chemical Society. All rights reserved.