Phosgene with enamines

Preparation. This a-chloro enamine (1) is prepared in about 80% yield by the reaction of phosgene with N,N-dimcthylisobutyramide followed by elimination of hydrogen chloride with triethylamine. ... 

Acylation with phosgene occurs under very mild conditions to give enamino-acyl chlorides which undergo solvolysis to esters or amides (Scheme 93). Cyanogen chloride reacts with enamines to give cyanoenamines and a-cyanoketones on hydrolysis. Cyanogen bromide and iodide react differently a 1 1 adduct is formed which, on hydrolysis, leads to 2-haloketone (Scheme 94). 

In the reaction of monosubstituted aliphatic carboxylic acid amides with phosgene, the enamine intermediate can be preferentially reacted with phosgene to form the carbamoyl chlorides XI, a valuable group of chemical intermediates ( °). 

Miscellaneous Reactions. Enamines of quinuclidone have been elaborated to give ketones of type (63), and enamines of piperidones to give further 3-azabicyclo[3,3,l]nonanes. The bridgehead urea (64) was obtained by the reaction of phosgene with (65), Portoghese has extended the preparation... 

Acylation of the Leimgruber Batcho enamines with phosgene followed by methanolysis and reductive cyclization generates methyl indole-3-carb-oxylates[8]... 

Villsmeier reaction on the dimethylacetal of methoxyacetaldehyde (141) with phosgene and dimethyIformamide affords the acrolein derivative, 142. Condensation of this with guanidine gives the pyrimidine, 143. (The enamine can be viewed as a latent aldehyde-the dimethylamino group is probably lost in the course of an addition elimination reaction with one of the guanidine groups.) This pyrimidine serves as starting material for sulfameter (111). ... 

An excess of phosgene has to be avoided if a-hydrogens are present, because the tautomeric enamines react with phosgene to produce chloro-vinyl N-carbonyl chlorides (see Chapter 8). 

Reaction of enamines with phosgene / -Amino-a,/ -ethylenecarboxylic acid esters... 

An ethereal soln. of the startg. enamine and triethylamine added at -20 to -10° to phosgene, the resulting triethylamine hydrochloride removed by filtration, and the filtrate treated dropwise at -20 to -10° with methanol and triethylamine methyl a-phenyl-/ -pyrrolidinoacrylate. Y 78%. - The reaction of enamines with phosgene occurs under mild conditions and provides reactive intermediates for the synthesis of / -ketocarboxylic acid derivs. and heterocyclics. F. e. and reactions s. A. Halleux and H. G. Viehe, Soc. (C) 1970, 881. 

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