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The phenylhydrazones 1a‐d condensed with ethyl cyanoacetate to yield pyridazinones 2a‐d that reacted with sulphur in presence of piperidine to yield the aminothienopyridazineones 3a,b that reacted with electron poor olefins and acetylenes to yield phthalazines 10‐12. The condensed aminothiophenes 3a,b reacted with dimethylformamide dimethylacetal to yield amidines 13a,b. Compounds 2a,b condensed with dimethylformamide dimethylacetal to yield the trans enamines 16a,b that cyclized readily into the pyridopyridazinones 17a,b on treatment with ammonium acetate in presence of acetic acid. Compounds 2a‐d reacted also with benzylidenemalononitrile to yield the phthalazinones 21a‐d. The reactions were conducted both by microwave heating and conventional heating. Better yields in much shorter reaction times were achieved by microwave heating.

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Reaction of enaminones 1a–d with 2-aminoprop-1-ene-1,1,3-tricarbonitrile (2) in the presence of AcOH/NH4OAc afforded 7-amino-5-oxo-5,6-dihydro-1,6-naphthyridine-8-carbonitrile derivatives 9a–d. On the other hand, 2-aminopyrano[4,3,2-de][1,6]naphthyridine-3-carbonitriles 20a–c,e were the only obtained products from the reactions of 1a–d with 2 in the presence of AcOH/NaOAc, while 1d afforded [3,5-bis-(4-chloro-benzoyl)-phenyl]-(4-chloro-phenyl)-methanone 21 under the same condition. The reaction of 2 with diethyl acetylenedicarboxylate in the presence of AcOH/NH4OAc afforded (4-cyano-5-dicyanomethylene-2-oxo-2,5-dihydro-1H-pyrrol-3-yl)-acetic acid ethyl ester 15B.

In conjunction to previous recent interest in adopting microwaves as energy source for synthesis of polyfunctional heteroaromatics [1-5], we report here efficient synthesis of title compounds utilizing 1a-d as starting materials and microwaves as energy source. The title compounds are biologically interesting molecules and their chemistry and pharmacology is receiving considerable recent interest [6][7][8]. Moreover utilizing microwaves as environmentally eco-friendly energy sources is being also now explored [9][10][11][12].The starting 1a-d condensed with ethyl cyanoacetate on heating in focused microwave at 170 ºC for 4 minutes in presence of ammonium acetate to yield pyridazinones 2a-d in 52 to 62% yields. The same compounds could also be obtained on heating 1a-d with ethyl cyanoacetate in acetic acid and in presence of ammonium acetate for ten hours, in 50 to 55% yields.The pyridazinones 2a-d readily reacted with sulphur in presence of piperidine on heating in a focused microwave oven for 5 minutes in dioxane as reaction medium to yield aminothienopyridazines 3a,b in 74 and 76% yields. Again thienopyridazines 3a,b were obtained in 69 and 72% yields on refluxing 3a,b with sulphur in DMF solution in presence of piperidine for 4 hours. The synthesis of 2 and 3 is an extension to our previously well-established synthesis 3-carboxylic ester derivatives of 2 and 3 [13][14][15].Compound 3b reacted readily with ethyl acrylate 4, maleimide 5a and N-methylmaleimide 5b in a mixture of acetic acid and dioxane in focused microwave at 210 ºC for 15 minutes and compounds 3a,b reacted with naphthoquinone 6 in ethanol at 100 ºC for 15 minutes in focused microwave to yield products of addition and hydrogen sulphide elimination. These products were also obtained on refluxing 3a,b with 4-6 in the same solvents for 8 hours.The condensation products of 3 with 4-6 were assumed to be formed via intermediary of 4+2 cycloadducts 7-9 which readily loses hydrogen sulphide to yield products 10-12 respectively. In no case C-1 alkylation products of thiepines similar to those claimed earlier to be formed on reacting thienocoumarin with dimethyl acetylenedicarboxylate and ethyl propiolate were formed [16][17][18][19][20] (Scheme 1).