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The first known lithiated 1-azafulvene derivatives were generated by low-temperature halogen/metal interchange, with r-BuLi, from the corresponding brominated 6-diisopropylamino compounds 3b and 12. These Li species reacted with sundry electrophilic reagents to give products which, on basic hydrolysis, were converted into 5-mono-or 4,s-disubstituted pyrrole-2-carbaldehydes 10 and 16, respectively.The generation of pyrroles lithiated on a C-atom requires the presence of a N-substituent, and if a formal N-unsubstituted lithiopyrrole is desired, this N-substituent of which several types have been utilized [ 1-71 must be readily removable. It was of interest to us to examine the possibility of effecting C-metalation of the pyrrole nucleus in the absence, at least in the formal sense, of a protecting group for the N-atom'). We have now devised two complementary strategies which demonstrate that this is indeed a viable concept. The first of these, which has already been disclosed in preliminary form [lo], involves the lithiation of the readily available dimer of 6-(dimethylamino)-1-azafulvene and of the corresponding 3-bromo derivative. The lithiated species thus generated have provided access to a great variety of 4-or 5-mono-and 4,5-disubstituted 1H-pyrrole-2-carbaldehydes. A description of the second synthetic strategy constitutes the subject of this communication.The 3,4-disubstituted 6-(dimethylamino)-2-halo-I-azafulvenes, synthesized twenty years ago by von Dobeneck and coworkers [ 1 11, are readily hydrolyzed to the corresponding aldehydes under mildly alkaline conditions. It was, therefore, apparent that, if the proclivity for nucleophilic addition to C(6) of azafulvenes could be overcome [12] and barring stability problems, halogen/Li exchange of a 3,4-unsubstituted congener (see 3) would generate a lithiated 1-azafulvene derivative, functionally equivalent to 5-lithio-1 H -pyrrole-2-carbaldehyde. -doctoral fellow, 1987-1988. Syntex Research post-doctoral fellow, 1985-1986 have reported that 3,4-dlodo-lH-pyrrole is converted into the 1,3-dilithio derivative with BuLi (2 equiv.) in THF solution (-78") containing tetramethylethylenediamine, as judged by the formation of 4-iodo-lH-pyrrole-3-carbaldehyde (45 % yield), after quenching with dimethylformamide. This does not promise to be a generally useful process since 2-bromo-1H-pyrrole is not lithiated on a C-atom even with excess t-BuLi [9].

eulfur poisoning, and to attain a reasonable catalyst life the sulfur content must be less than 1 grain per 1000 cubic feet. The sulfur sensitivity of catalysts for the alcohol syntheses appears to vary considerably with catalyst composition. However, these catalysts are in most cases less sensitive to sulfur poisoning than Fischer-Tropsch catalysts. Some alcohol catalysts, for example, those for the iso synthesis, are unaffected by high concentration of sulfur (15). ACKNOWLEDGMENTThe authors are pleased to acknowledge the assistance of Charles Zahn and of R. A. Friedel in the analysis of the products obtained from the nitrided iron catalyst.