Pyridine-3,5-dicarboxylic ester, 1,4-dihydro

Esters of pyridine-dicarboxylic acids are reduced to dihydro-compounds by aluminium and wet ether o s ... 

Dimethyl-4-phenyl-l,4-dihydro-pyridine-3,5-dicarboxylic acid diethyl ester... 

A brief discussion of some aspects of alcohol dehydrogenase will be used to illustrate the potential for catalysis. This system is chosen for illustration because it has been studied so extensively. Lessons drawn can be applied in a broader context. The 1,4-dihydropyridine (2a) is the reductant and this affords a nico-tinium ion (1) on transfer of hydride, as illustrated in equation (1). This process is mimicked in many abiotic systems by derivatives of (2 R = alkyl or benzyl), by Hantzsch esters (7), which are synthetically readily accessible, and 1,4-dihydro derivatives (8) of pyridine-3,5-dicarboxylic acid. A typical abiotic reaction is the reduction of the activated carbonyl group of an alkyl phenylglyoxylate (9), activated by a stoichiometric amount of the powerful electrophile Mg(CI04)2, by, for example, (2b equation 8). After acrimonious debate the consensus seems to be that such reactions involve a one-step mechanism (i.e. equation 5), unless the reaction partner strongly demands a radical intermediate, as in the reduction of iron(II) to iron(III). 

Bennasar extended his research on 2- and 3-indolylacyl radicals to intramolecular cyclizations to yield 2,3-fused indoles [112], Under nomeductive conditions (n-Bu6Sn2, hv), radical 201 underwent a cascade addition-oxidative cyclization sequence with a number of alkene acceptors including dimethyl fumarate (45%), methyl 1-cyclohexenecarboxylate (53%), methyl crotonate (71%), vinyl sulfone (22%), and the a,p-unsaturated lactam ester, 2-oxo-5,6-dihydro-2H-pyridine-l,3-dicarboxylic acid dibenzyl ester (41%) to form cyclopenta[h]indol-3-ones 202. Reaction of 201 with acrylonitrile and methyl acrylate, however, generated cyclo-hepta[h]indoles, the products of bis-addition-cyclization sequences. 

Pyridonecarboxylic acid esters. F2 (diluted with N2) bubbled into a soln. of dimethyl pyridine-2,3-dicarboxylate in 2 1 acetonitrile/water for 20 min at 0 , flushed with N2 for 30 min at room temp., and refluxed for 2 h-+ dimethyl 1,6-dihydro-6-oxopyridine-2,3-dicarboxylate. Y 56%. F.e. inch oxidation of 2-, 3- and 4-carboxypyridines, and of methyl quinoline-4-carboxylate, s. M. Van Der Puy et al.. Tetrahedron Letters 29, 4389-92 (1988). 

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