A convenient synthesis of quinones from hydroquinone dimethyl ethers. Oxidative demethylation with ceric ammonijm nitrate.

(1) Part 3 of a series on pheromone synthesis. For part 2 see P. J. Kocienski and G. J. Cernigliaro, J. Org. Cbem., 41, 2927 (1976). (2) H. M. Fales, M. S. Blum, R. M. Crewe, and J. M. Brand, J. lflsect Pbysiol., 18, 1077 (1972). (3) J. A. Katzeneilenbogen and T. Utawanit, J. Am. Cbem. Soc., 96, 6153 (1974). (4) L. A. Carpino, J. Am. Cbem. SOC., 80,601 (1958); L. A. Carpino, P. H. Terry, and S. D. Thette, J. Org. Cbem., 31, 2867 (1966). (5) L. A. Carpino and E. G. S. Rundberg, J. Org. Cbem., 34, 1717 (1969), investigated some bicyclic halopyrazolinones in which R, and R2 were alkyl groups which formed part of a ring. in these cases, the €isomer was the exclusive product. (6) For a review see D. J. Cram, "Fundamentals of Carbanion Chemistry", Academic Press, New York, N.Y., 1965, pp 130-135. (7) The procedure used for the preparation of 7 was derived from A. P. Krapcho, J. Diamanti, C;. Cayen, and R. Bingham, "Organic Syntheses", Collect. Vol. V, Wiley. New York. N.Y., 1973, p 198: bp 102-105 OC (20 mm); ir(CC14) 1750, 1720 cm-'; NMR (CCI4) 6 3.7 (s, 3 H), 3.7 (q, 1 H), 2.7 (quintet, 1 H), 1.6(m,2H),1.3(d,3H),1.1(d,3H),O.9(t,3H). (8) The vinyl proton of the E isomers 5 were consistently shifted downfield -1 .O ppm from the corresponding Z isomers 6: G. Buchi and H. Wuest, Helv. Cbim. Acta, 50, 2440 (1967). (91 An alternative to the Scheme I mechanism entails hydrolytic cleavage of 2 to the vinyl diimide i which may then undergo radical decomposition to the observed products. ESR studies have shown that vinyl radicals invert