Curtius degradation, amines from

Two examples illustrate the formation of amino groups at 1- or 2-positions of dibenzopyridoazepines the route from carboxylic acid 354c by Curtius degradation through mixed anhydride to yield amine 391... 

General. Diphenyl phosphorazidate is a readily available, nonexplosive, and relatively stable azide widely used as a reagent in peptide synthesis, " and as a versatile reagent in a wide array of organic transformations. DPPA has been successfully utilized in the synthesis of a-amino acids and o-aryl carboxylic acids direct preparation of thiol esters from carboxylic acids and thiols the stereospecific preparation of alkyl azides and the phosphorylation of alcohols and amines The application of DPPA in a modified Curtius reaction permits a simple one-step conversion of carboxylic acids to urethanes under mild reaction conditions. DPPA acts as a nitrene source, and can undergo 1,3-dipolar cycloaddition reactions. The Curtius degradation of carboxylic acids in the presence of f-butanol gives the Boc-protected amine directly (eq 1). 

Phenylcyclopentylamine has also been prepared from 1-phenylcyclopentanecarboxylic acid by means of the Hofmann degradation of the intermediate amide4 6 and from the intermediate carboxylic acid chloride by the Curtius reaction.6 In the method described, using the mixed carboxylic-carbonic anhydride,7 improved yields of the amine are obtained. 

Arylfurazancarboxamides on treatment with alkaline hypochlorite undergo Hofmann degradation to the amines likewise carbamates result from Curtius rearrangement of furazanylacyl azides in the presence of alcohols. 

Phenylethylamine has been made by a number of reactions, many of which are unsuitable for preparative purposes. Only the most important methods, from a preparative point of view, are given here. The present method is adapted from that of Adkins,1 which in turn was based upon those of Mignonac,2 von Braun and coworkers,3 and Mailhe.4 Benzyl cyanide has been converted to the amine by catalytic reduction with palladium on charcoal,5 with palladium on barium sulfate,6 and with Adams catalyst 7 by chemical reduction with sodium and alcohol,8 and with zinc dust and mineral acids.9 Hydrocinnamic acid has been converted to the azide and thence by the Curtius rearrangement to /3-phenyl-ethylamine 10 also the Hofmann degradation of hydrocinnamide has been used successfully.11 /3-Nitrostyrene,12 phenylthioaceta-mide,13 and the benzoyl derivative of mandelonitrile 14 all yield /3-phenylethylamine upon reduction. The amine has also been prepared by cleavage of N- (/3-phenylethyl) -phthalimide 15 with hydrazine by the Delepine synthesis from /3-phenylethyl iodide and hexamethylenetetramine 16 by the hydrolysis of the corre-... 

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