CONFORMATIONAL ANALYSIS OF SATURATED HETEROCYCLES .20. STEREOCHEMISTRY OF BASE-CATALYZED HYDROGEN-DEUTERIUM EXCHANGE OF METHYLENE PROTONS ALPHA TO A SULFINYL GROUP

The base-catalyzed hydrogen-deuterium exchange of the α-sulfinyl protons in the conformationaly rigid cis- and trans-4-phenyltetrahydrothiopyran 1-oxides is stereoselective in water and methanol-1-d and nonstereo-selective in t-butyl alcohol-and dimethyl sulfoxide-methanol. The kinetics in methanol-1-d are interpreted in terms of two competing pseudo-first-order reactions, one for the α-axial proton and one for the α-equatorial proton. The order of proton acidity adjacent to a sulfinyl group is concluded to be (a) trans to S=O and gauche to sulfur lone pair, (b) gauche to S=O and to sulfur lone pair, (c) gauche to S=O and trans to sulfur lone pair. © 1969, American Chemical Society. All rights reserved.