Recent Advances in the Synthesis of Polysubstituted Heterocycles

Multicomponent reactions under increased pressure: on the reaction of arylhydrazonals, aromatic aldehydes and malononitrile in Q-Tube

“…Although, in a previous article, Moustafa et al [18] reported the formation of pyridazino [5,4,3-de] [1,6]naphthyridine derivatives via reaction of ethyl 3-oxo-2-arylhydrazono butanoate, malononitrile and aromatic aldehydes under high pressure but they could not conclude exact mechanism of the process leading to the formation of the tricyclic system. In our efforts described above the reactions are also conducted in a Q-tube, as in more than one situation, products resulting from initial condensation with malononitrile as the case of compound 1j and 1k and subsequent reaction with arylidene malononitrile have been observed which decisively excluded the initial dimerization of malononitrile.…”

“…Our contributions have been recently surveyed [1]. We have also recently surveyed utility of multicomponent reactions in our area [2].…”

Multi Component Reactions under Increased Pressure: On the Mechanism of Formation of Pyridazino[5,4,3-de][1,6]naphthyridine Derivatives by the Reaction of Malononitrile, Aldehydes and 2-Oxoglyoxalarylhydrazones in Q-Tubes

“…The considerable biological and medicinal activities of pyridazines has stimulated considerable research on efficient syntheses of these derivatives in past years [ 1 , 2 , 3 , 4 ]. Elnagdi et al reported synthesis of 2-amino-1,4-dihydropyridazine, an isoelectronic derivative of 1,4-dihydropyrimidines of established biological activities [ 5 , 6 , 7 , 8 ], via 3 + 3 atom combination of arylhydrazones 1a and α,β-unsaturated nitriles 2 [ 9 ] or by reacting a mixture of 1 , 4 and 5 in one pot ( Scheme 1 ). Subsequent studies [ 10 , 11 ] on this novel route revealed however that it is of a limited scope as the reaction products proved to be dependent on the nature of the reacting aryl hydrazones.…”

Organobase-catalyzed three-component reactions for the synthesis of 4H-2-aminopyrans, condensed pyrans and polysubstituted benzenes

“…The synthesis of 2-amino-4 H- pyrans by these reactions has recently been surveyed. Since the first report describing the preparation of 2-amino-4 H -pyrans by the addition of active methylenenitriles to α,β-unsaturated ketones [8], 2-amino-4 H -pyrans 1 (Scheme 1) have become the central focus of a number of chemical and biological investigations [9–10]. …”

“…Elnagdi et al reported [ 13 ] that reaction of alkyl azenyl carbonitrile with arylidene malononitrile afforded benzo-fused azenes. Based on these studies several surveys were published during the last decade [ 10 , 14 – 19 ].…”