Thiobenzophenone with 1,4-dihydropyridines

In general only very electron-deficient double bonds will react spontaneously with 1,4-dihydropyr-idines. (This statement applies to nonenzymic chemistry enzymatically, as in LAD, NAD(P)H, with a lesser reduction potential than many of the 1,4-dihydropyridines used in abiotic reactions, reduces unactivated carbonyl groups.) Thiobenzophenone, quinone, maleic acid, and hexachloroacetone react spontaneously with simple dihydropyridines and undergo reduction (the carbon-carbon double bond of maleic anhydride is reduced). Trifluoroacetophenone will also often react spontaneously with 1,4-dihydro-pyridines. 

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