708 T. Torres, SV Eswaran, W. Schäfer Vol. 22 quiñones were prepared from 3 and 10 by oxidative cycli- sation using lead tetraacetate [1]. Because of low solubility of compounds 1 in organic solvents and the inability to purify them by chromatography they may contain small amounts of 3; impurities of 0.5% or less cannot possibly be detected by tic in this case. If indeed quiñones 3 and 10 are reaction products, one has to think of a stabilization of a triplet nitrene by proton ...