Nitro acyl halides, preparation

The reactions of the homocyclic ring of benzofuroxans, which are described in detail in Section 4.22.3.3, provide access to numerous derivatives. Nucleophilic displacement of halides is facile when activating nitro groups are present, allowing alkoxy, aryloxy, thio and amino groups to be introduced. Electrophilic substitutions, e.g. nitration, are also valuable. Further transformations may also be performed on benzo-ring substituents. Such modifications include acetoxy to hydroxy acetamido to amino and acyl halides to esters and amides. Some reactions of the substituents of monocyclic furoxans allow hetero-substituted analogues of benzofuroxans to be prepared. For example, pyridazinofuroxans are formed by condensation of diacylfuroxans with hydrazine. 

The N -substituted N-imines can be prepared by the reaction of the N-aminoazonium salts, in the presence or absence of base, with anhydrides or acyl halides,8,13-17,20,21,45,46 diketene,47 diethyl malonate,48 sulfonyl chloride,8,15,49,50 /i-halovinyl ketones and esters,51-54 diethyl ethoxymeth-ylenemalonate and related compounds,53,55-57 isocyanates,17,58 thioiso-cyanates,17,58 imidoyl chlorides and imidates,59,60 nitro acetate,8,61 and active halobenzenes.62,63 Some representative pyridine -(substituted imines) prepared in this way are shown in Scheme 1. 

The corresponding iV-nitroamides (31) decompose under similar conditions to yield similar products (equation 113). The nitro-amides are useful in that the critical intermediate 32 can be prepared by an independent path—the reaction of a nitroamine salt (33) with an acyl halide, a reaction that can be studied at much lower temperatures than are feasible for the decomposition of the nitroamides... 

Aromatic compounds with nitro groups ortho to the alkyne have been converted into indoles (eq 9). Alkynyl ketones have been prepared from either the corresponding acyl halides or by carbonylative ethynylation of vinyl halides and triflates with TMSA. 

A new simple and direct procedure (Scheme 29) for the a-acylation of nitromethane has allowed the preparation of a variety of a-nitro-ketones. The familiar imidazolide acylating agents (46) are easily prepared, either in situ from the carboxylic acid and 1,1-carbonyldi-imidazole or from the acyl halide and two equivalents of imidazole. 

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