Reduction of nitro-compounds by triethyl phosphite or triphenylphosphine has been examined. Thus, 2-nitrobiaryls are readily reduced t o carbazoles in high yields in boiling triethyl phosphite after 8 hr. 2-o-Nitrophenylpyridine similarly gives yyrido[ 1 , 2-blindazole in almost quantitative yield ; anils such as o-nitrobenzylideneaniline give 8-arylindazoles , 2-nitroazobenzenes give 2-aryltriazoles, and a-nitrostilbene and cis-or trans-2-nitrostilbene give 2-phenylindole. Other related deoxygenations have been carried out and the scope of the reduction is indicated.BUNYAN and CADOGAN recently demonstrated that aromatic C-nitroso-compounds are readily deoxygenated by triethyl phosphite or triphenylphosphine to give a variety of products dependent on the nature of the nitroso-compound : carbazoles, for example, being readily formed from the corresponding 2-nitrosobiaryls. The preparative significance of this reaction is reduced, however, by the difficulties sometimes encountered in the preparation of the nitroso-compound from the corresponding nitrobiaryl. It was therefore of interest to investigate the possibility of in situ preparation and subsequent reduction of the nitroso-compound by reaction of the parent nitro-compound with an excess of triethyl phosphite.At the outset of this investigation , very few reactions of nitro-compounds with tervalent organic compounds of phosphorus had been reported and in many of these the nitro-group remains intact. Thus, Horner and Klupfel showed that o-dinitrobenzene and o-nitrobenzaldehyde react reversibly with triethylphosphine to give unstable 1 : 1-adducts , 0-and 9-nitrobenzaldehyde undergo apparently irreversible additions with trialkyl phosphitesJ4 while nitrobenzene was recovered unchanged from a similar r e a~t i o n .~ The reaction of triphenylphosphine with 4-nitropyridine 1-oxide at 200°, on the other hand, led to the evolution of nitrous fumes, the fate of the remainder of the molecule being undetermined . 5 It has now been shown that 2-nitrobiaryls (I; R = H, 2'-C1, 2'-Br, 4'-Br, 2'-Me, 4'-Me) react with triethyl phosphite at the boiling point to give good yields of the corresponding carbazoles (11) and triethyl phosphate; i.e., under much more vigorous conditions than those necessary to effect the corresponding reduction of 2-nitrosobiaryls. 1-o-Nitrophenylnaphthalene, which presents two possible points of ring closure, also reacted to give a * Preliminary accounts of this work have appeared: J. I. G. Cadogan and M. Cameron-Wood, Proc.l Part XVIII, A.

IN our synthetical work on " tagetone '' we prepared the two stereoisomers of 3-methylpent-2-en-4-ynal (I) and encountered their ready conversion into a ca. 98 : 2 cis-transequilibrium mixture. The known stereoisomeric 3-methylpenta-2,4-dienols were also