Carboxylic acid amides ketene addition

Without additional reagents Synthesis of carboxylic acid amides from ketene aminals via amidinium salts... 

Carboxylic acid anhydrides. A soln. of triflic anhydride in ethylene dichloride added dropwise to a soln. of Ph3PO in the same solvent at 0° under N2 after 15 min a soln. of / -toluic acid in ethylene dichloride added followed by EtjN, and stirred for 15 min - p-toluic anhydride. Y 93%. Redox side reactions are avoided, and ketones, esters and ethers unaffected. F.e. inch ketenes, carboxylic acid esters (incl. aryl esters) and amides, amidines from carboxylic acid amides, benzimidazoles, and intramolecular ar. acylation, also using N-diphenylphosphinyl-N -methylpiperazine (without the need for an additional base), s. J.B. Hendrickson, M.S. Hussoin, J. Org. Chem. 54, 1144-9 (1989) alternative prepn. of reagents cf. D. Crich, H. Dyker, Tetrahedron Letters 30, 475-6 (1989). 

Another conjugate addition strategy used the sodium enolate of 4.62 in a reaction with ketene 4.63 to give 4.64. In this particular example, both the amino and the carboxyl moieties of the final amino acid were present in the starting material (4.62). Aqueous acid hydrolysis of the ester groups and the amide was accompanied by decarboxylation to give 2-amino-3-methylenebutanedioic acid, 4.55.33... 

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