Cyclopentenolones of type (1) constitute the alcohol fragment of the natural rethrins. Knowledge of their oxidation reactions is of general interest in connection with the rapid and little understood deterioration of such insecticidal films. During a study of the reaction between manganese dioxide and the synthetic model compound (+)-allethrolone (1, R=H) we have found that, in addition to the expected dione (2, R=H), oxidative coupling occurs to give the novel tetraone (3).* Shaking allethrolone (1, R=H) with finely ground manganese dioxide' in carbon tetrachloride at 2S", rapidly produced the cyclopentenedione (2, R=H), b.p. 62-64'10.3 mm., -4 1.5170, xmax (EtOH) 242 mu (E 12,600) vmax (film) 1745: 1705 (C=O, cyclopentenedione2'3), 1640, 1266, and . 995, 925 (terminal vinyl) cm. -l, r 4.15 ddt (2 16,9,6)(-CH2-Cfl'CH2), 4.7-5.1 m (-CH=Cl%,), 6.77 d (26>(-CH2-CH=>, 7.12 (-COCH2CO-)(disappears on treatment D20/Na2C03/T.H.F.), 7.94 (=C.CF13), m/e 150 , e-2,4_dinitrophenylhydrazone m.p. 256' (EtOH/C6H5N02). Quantitative study indicated that 0.53 g. of allethrolone required 4.4 g. (14.7 equivs.) of manganese dioxide (from the batch used) to convert it to (2, R=H)(60X) in 5 min., and longer periods of reaction did not diminish this yield.
*
This compound was isolated and investigated independently in our two laboratories.