5-Amino-4-(cyanoformimidoyl)-1H-imidazole (3) has been prepared in good yield by the base-catalysed cyclisation of (Z)-N-(2-amino-1,2-dicyanovinyl)formamidine. Compound (3) reacts with ketones, R¹COR²[R¹= R²= Et, Me, Bu, –(CH₂)₅–, PhCH₂; R¹= Me, R²= Ph] togive2,2-disubstituted-6-carbamoyl-1,2-dihydropurines as the major products, together with minor amounts of compounds believed to be novel 7-amino-1-carbamoyl-3,3-disubstituted 3H-imidazo[1,5-c]imidazole derivatives, which have been isolated when R¹= R²= Et, Bu, and PhCH₂; when R¹= R²= Ph the only product isolated is tentatively assigned the imidazo[1,5-c]imidazole structure. In the reaction with acetylacetone the 1,2-dihydropurine intermediate is unstable and loses acetone to give 2-methyl-6-carbamoylpurine. The aldehydes RCHO [R = Me, Et, (E)-MeCHCH–, c-C₄H₄O] also react readily with (3) at room temperature to give the corresponding 6-carbamoyl-1,2-dihydropurine derivatives, which can be isolated when R = Me or Et; these oxidise in solution to afford the corresponding 6-carbamoylpurines.

The reaction of ethyl (Z)-N-(2-amino-1,2-dicyanovinyl)formimidate with hydrazine monohydrate leads to (Z)-N³-(2-amino-1,2-dicyanovinyl)formamidrazone in almost quantitative yield. This compound proved to be an important starting material for the synthesis of the corresponding N¹-isopropylidene-and N¹-acetyl-formamidrazones. The amidrazones prepared promptly cyclize in the presence of base to give a 1,5-diamino-4-cyanoimidazole or a 1,5-diamino-4-(cyanoformimidoyl)imidazole, depending on the reaction conditions and mainly on the nature of the base used to induce cyclization. 1,5-Diamino-4-(cyanoformimidoyl)imidazole was treated with carbonyl compounds and the 1,2-dihydropurines thus isolated indicated that the amino group in position 5 is more reactive than that in position 1.

Reactions of the methyl 2-aryl-2H-azirine-3-carboxylates 1a and 1b with nucleophiles are described. Thiols add to the CN bond to give aziridines 4–6. Propargyl alcohol similarly gives the aziridine 7. Primary and secondary aliphatic amines react with the azirines to give methyl 3-aminoacrylates 8–12. 4-Cyclohexen-1-ylmorpholine and 1-cyclopenten-1-ylpyrrolidine react with the azirine 1a to give products formulated as the aziridine 13 and the vinylidenecyclopentanone 14, respectively, in contrast to previously reported reactions of enamines with azirines from which pyrroles were isolated. Acetylacetone gives a pyrrole-3-carboxylate 15 in low yield with the azirine 1a. All these products have been rationalised by invoking initial addition of the nucleophile to the CN bond of the azirine. The tetrahydrofuran-2-yl radical also adds to the CN bond of the azirine 1a, giving the aziridine 16 as a single diastereoisomer. X-Ray crystal structures of methyl (E)-3-amino-3-(2,6-dichlorophenyl)-2-morpholin-4-ylpropenoate 8 and of methyl 3-(2,6-dichlorophenyl)-2-(tetrahydrofuran-2-yl)aziridine-2-carboxylate 16 are reported.

Diels–Alder reactions of the methyl 2-aryl-2H-azirine-3-carboxylates 1a and 1b have been investigated in order to determine the stereoselectivity and regioselectivity of the reaction. The azirines react with a range of electron rich dienes at room temperature to give Diels–Alder adducts. The reaction leads to the formation of endo-cycloadducts with both cyclic and acyclic dienes; furan is exceptional in giving an exo-adduct 7. X-Ray crystallography has established the structure 9 of the Diels–Alder adduct formed from the azirine 1a and 1-acetoxybutadiene. The same regioselectivity, in which the more nucleophilic terminus of the diene combines with the carbon atom of the CN bond, is found in the adducts from several other 1- and 2-substituted dienes. Only isoprene, among the dienes examined, gives a mixture containing the opposite regioisomer 14 as a minor component.