Synthesis of novel functionally substituted pyridazines and oxazines

Abstract

Although β-aminoenones and β-nitroenamines are already established as synthetic intermediates, particularly, in heterocyclic chemistry [1][2][3][4][5], the utility of phenylhydrazones and oximes, which have closely related structures to them, is little studied [6][7][8]. In this paper we describe the reaction of cyanoolefins 1 with diphenylhydrazone 2 and dioxime 3 as a route to functionally substituted pyridazines and oxazines, respectively.The reaction of electrophiles such as compound 1 with nucleophiles such as compound 2 is of interest because it may occur either at the nitrogen atom of the NH group or at the carbon atom of the cyano group. Thus, condensation of diphenylhydrazone 2 [9] with activated cyanoolefins 1a-c in a molar ratio of 1:2 in refluxing ethanolic piperidine afforded 3,3'-carbonylbis(6-amino-4-aryl-5-cyano-1-phenylpyridazine) 4a-e (Scheme 1).The structure of compound 4 was established for the reaction product, and the structure 5 was excluded, based on analytical and spectral data (cf. Experimental). The 1 H NMR spectrum of compound 4c exhibited a four proton singlet at δ 5.55 (s, 2NH 2 ), a two-proton singlet at δ 4.42 due to H-4 of pyridazine, and eighteen proton multiplets at δ 7. . N N N N O C 6 H 5 C 6 H 5 NH 2 N H 2 CN NC Ph Ph m/z 273 m/z 301 4a The mass spectrum of compound 4a showed a molecular ion at m/z 573 [M + -H], m/z 273 [pyridazine], m/z 301 [pyridazine-CO], m/z 196 [pyridazine-C 6 H 5 ], and m/z 77 base peak [C 6 H 5 ].

KAl(SO4)2.12H2O (Alum) Reusable An Efficacious Heterogeneous Catalyst for the One-Pot Synthesis of Some New spiro[imidazo[1,2-a]pyridine-7,3'-indole]-2',5(1'H,6H)-dione Derivatives

“…Recently, many other methods indicate the use of Lewis acids [30,31], protic acid (TFA) [32], or base (NaHCO 3 ) [33], piperidine (three-component reaction, 4h) [34], and piperidine (four-component reaction, 12-14h) [35] for synthesis of imidazo [1, 2-a] pyridine, but the preparation of corresponding spiro[imidazo[1,2-a]pyridine-7,3'-indole]-2',5(1'H,6H)-dione analogs has not yet been evolved.…”