3-Cyano-3,4-dihydropyridin-2-ones

Utilization of acetic acid (90CCC718, 95BML2783) and mixtures of acetic and sulfuric acids (81JHC309), as well as triphenylmethylborofluor-ide (86JPR35), leads to 3-cyano-3,4-dihydropyridin-2-ones, which can be oxidized into the corresponding cyanopyridones by nitrosylsulfuric acid. Authors (81JHC309) have studied the synthesis of 3-cyanopyridones 264 systematically, and have shown that the latter can be obtained by different routes from 2-amino-4H-pyrans 59, as well as from related dihydro- 265 and tetrahydropyridone 266 (Scheme 104). 

Hantzsch esters (e.g. 2,6-dimethyl-l,4-dihydropyridine-3,5-dicarboxyUc acid diethyl ester), analogues of NAD(P)H, transfer hydride from the 1- and 4-positions, the question of which occurs first may be resolved by the use of a probe such as (Z)-ethyl Q -cyano-jS-bromomethylcinnamate, which will only accept one hydride since it rapidly cyclizes after the first addition to give a cyclopropane derivative. The use of 1- and 4-deuterium-labelled Hantzsch esters indicated that it is the 4-proton that is transferred first. ... 

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