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Mass.Hydrogen removal has been shown to be at least partially rate determining in the reaction of MA0 with substrates: 8. Belleau and J. Moran, Ann. N. Y. Acad. Sci., 107, 822 (1963). The quaternary salts 10, 11, and 12 were prepared from the reaction of the corresponding unsaturated bromides or mesylate with trimethylamine. Solubilization of 10 in neutral deuterium oxide (25 'C) leads instantaneously (on the NMR time scale) to exchange of the terminal, acetylenic proton. The overwhelming preference for removal of propargyl vs. allylic protons is in accord with the much greater electron-withdrawing power of the ethynyl group than the vinyl g r~u p .~* -~' J. A. Landgrebe and R. H. Rynbrandt, J. Org. Chem., 31, 2585 (1966). T. L. Brown, Chem. Rev., 58, 595 (1958). R. W. Taft, Jr., in "Steric Effects in Organic Chemistry", M. S. Newman, Ed., Wiley, New York, N.Y., 1956, p 619. That negative charge is more rapidly generated at a site adjacent to a triple bond than at an allylic site is also known from studies of base-catalyzed isomerizations of allenes and acetylenes: R. J. Bushby, Quart. Rev.. 24, (1970).(a) The strong preference for removal of a propargyl proton compared to an allyl proton stands in contrast to the ease of removing the cwespondlng hydrogen atoms. The most recently determined value for propargyl stabilization is 4.8 kcal/mol (R. Walsh, Trans. Faraday Soc., 84, 2085 (1971)). which is considerably smaller than the commonly quoted value of 12 kcal/mol for allylic stabilization (P. Nangia and S. W. Benson, J. Am. Chem.

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apparatus and the distillate was examined by analytical GC °C depending on sample) and TLC (30% ether/ petroleum ether). Ketol 7, when present, appeared at a longer retention time and a smaller R¡ than enone 6. The product yields and physical data are recorded in Tables I and II. In some instances analytical samples were obtained by preparative GC or TLC.Method B. To a solution of 4 mmol of alcohol 4 in 6 mL of dry pyridine was added 2 mmol of phosphorus oxychloride, and the solution was refluxed under nitrogen for 2.5 h. The reaction mixture was cooled, 15 mL of water was added, and the cloudy mixture was extracted three times with ether (total volume ~100 mL). The combined organic phases were extracted with cold 6 N HC1 until all the pyridine was removed. The ether solution was transferred to a round-bottomed flask, 20 mL of 2 N HC1 was added, and the two-phase system was vigorously stirred at room temperature for 18 h to effect hydrolysis of the enol ether moiety. The aqueous phase was separated and extracted three times with ether, and the combined organic phases were extracted once with saturated NaHC03 solution and once with brine and then dried. After removal of the solvent, the residue was distilled with a Kugelrohr apparatus and analyzed by GC and TLC. Generally a small amount of unhydrolyzed diene 5 was detected and was found to have a shorter retention time and a larger Rf than those for enone 6.10 The yields of enone 6 for this procedure are reported in Table I.Conversion of 4 to Ketol 7. A solution of 4-5 mmol of crude Grignard product 4 in 100 mL of ether was stirred vigorously for 18 h with 25 mL of 5% H2S04. After the aqueous phase was extracted three times with ether, the combined organic phases were extracted once with a saturated NaHCOg solution and once with brine and then dried with anhydrous MgS04. Removal of the solvent yielded ketol 7 which exhibited carbonyl absorption at 1720 cm"1 in its IR spectrum and a singlet methyl carbinol resonance at 8 1.3 in its NMR spectrum.Acknowledgments. The authors acknowledge the financial assistance of the National Research Council of Canada.