Synthesis of Phenylthio Substituted 4H-Pyrans and 2-Pyridinones by Conjugate Addition-Cyclization of CH-Acids to α,β-Unsaturated Ketones

Abstract

The conjugate addition of malononitrile to ,-unsaturated ketones catalyzed by piperidine yielded 2-amino-4-aryl-6-methyl-5-(phenylthio)-4H-pyran-3-carbonitriles. The reaction of ,-unsaturated ketones with cyanoacetamide led to 2-pyridone derivatives. The reaction of malononitrile and ethyl cyanoacetate with an enaminone occurred under elimination of dimethylamine to yield 2-pyridone.

Synthesis and characterization of some new 4,4′-(1,4-phenylene)dipyrimidine and 6,6′-(1,4-phenylene)-di(pyridin-2(1H)-one) derivatives

“…From this evidence, the mechanistic picture for the pyridone-forming process emerged as shown in Scheme 3. Seemingly, addition of 11 to 2 gives rise to the Michael adduct 12 which subsequently eliminates dimethylamine and undergoes cyclization to the imino-pyran 14 as an intermediate [35]. The presence of piperidine and dimethylamine in the reaction mixture promotes ring transformation of 14 to the corresponding pyridin-2(1H)-one 15.…”

Synthesis of fused uracils: pyrano[2,3-d]pyrimidines and 1,4-bis(pyrano[2,3-d]pyrimidinyl)benzenes by domino Knoevenagel/Diels-Alder reactions

“…The same α,β-unsaturated carbonyl compounds, obtained by Knoevenagel condensation of the appropriate CH acids and aromatic aldehydes, can be used as substrates in pyran synthesis by conjugate addition-cyclization with malononitrile or cyanoacetate [27–29]. Pyrano[2,3- d ]pyrimidine derivatives can be prepared by conjugate addition-cyclization of malononitrile to 5-arylidenebarbituric acids, or general procedures include the reaction of arylidenemalononitriles with barbituric acids under traditional hot reaction conditions [30, 31] or under microwave irradiation [32].…”