Ethyl iminoacetates

The N-alkylation of L-cysteine results from a series of reactions involving the condensation of L-cysteine methyl ester (605) with ethyl iminoacetate (606), followed by A-alkylation of the intermediate 4-methoxycarbonyl-2-methylthiazoline (607). Acid hydrolysis of the thiazolinium salt (608 Scheme 301) then gives (609) (70ACS(B)3129). 

Esterification, crotonic acid, 149 levulinic acid, 157 thiophene-2-carboxylic acid, 182 o-toluic acid, 162 Ester interchange, 152 Ethanolysis of ethyl iminoacetate, 159 Ether cleavage with HBr, 271... 

A soln. of ethyl carbazate in abs. ethanol added dropwise at 0-10° to a stirred ice-salt-cooled soln. of ethyl iminoacetate hydrochloride in the same solvent, and the product isolated after 4 hrs. stirring below 10° ethyl acetate carbethoxyhydrazone (Y 10%) heated 1 hr. at 150° with excess aniline 3-hydroxy-4-phenyl-5-methyl-l,2,4-triazole (Y 10%). F. e. s. M. Pesson, S. Dupin, and M. Antoine, G. r. 253, 285 (1961). 

Treatment of the iminoacetate 152 with 4-chlorobenzoyl chloride in the presence of a base gave the desired ethyl 5-(4-chlorophenyl)-l-(2,4-dichlorophenyl)-17/-l,2,4-triazolecarboxylate 153 and the uncyclised ethyl 2-(4-chlorobenz-amido)-2-(2-(2,4-dichlorophenyl)hydrazinyl)acetate 154 in 36% and 6% yield, respectively. The undesired compound 154 was subsequently converted to 1,2,4-triazole 153 in 93% yield by further treatment with pyridine (Equation 47) <2006EJM114>. 

Table 22.9 Reductive coupling of 1,3-enynes with ethyl (N-tert-butanesulfinyl)iminoacetate.

Kong, J.-R., Cho, C.-W., Krische, M. J. (2005). Hydrogen-mediated reductive coupling of conjugated alkynes with ethyl (Ai-sulfinyl)iminoacetates Synthesis of unnatural a-amino acids via rhodium-catalyzed C-C bond forming hydrogenation. Journal of the American Chemical Society, 127, 11269-11276. 

Scheme 6 Reductive coupling of 1,3-enyne to ethyl (iV-sulfmyl)iminoacetates...

---