Orthoamide und Iminiumsalze, LXXVI [1]. Ein weiterer Beitrag zur Chemie der Trialkoxyacetonitrile/ Orthoamides and Iminium Salts LXXVI [1]. A Further Contribution to the Chemistry of Trialkoxyacetonitriles

Abstract

An improved procedure for the preparation of trimethoxyacetonitrile (3a) starting from trichloroacetonitrile and sodium methanolate is described. Carbanions, obtained by the action of sodium hydride on nitriles, ethyl acetate and methylketones, react with trialkoxyacetonitriles 3 to give α- imino-orthocarboxylic acid trialkylesters 12, 14 and 20, which form an equilibrium with the tautomeric enamines 13, 15 and 21. The enamines 21 react with N,N-dimethylformamide dimethylacetal (24) to give amidines 25 which are cyclized to pyridinium salts 28 and 29 on treatment with benzyl bromide and acetyl chloride, respectively. The reaction of the enaminonitrile 13a with the orthoamide derivative of phenylpropiolic acid 30 affords the pyridine-2-orthocarboxylic acid trimethylester 31. The N,O-protected 4-hydroxy-piperidine 35 can be deprotonated by means of sec-butyl lithium. The carbanions thus formed are trapped with D2O, dimethyl sulfate, phenylisocyanate, CO2, and dimethyl carbonate delivering the piperidine derivatives 37 - 41. The heterocyclic orthoester 43 can be prepared analogously from 35 and 3a. The piperidine derivatives 44, 46 and 47 are prepared from the N,O-protected piperidines 39 and 41.