Unexpected formation and X-ray structure of tetramethyl 4,5-bis(dimethylamino)-2,3,6,7-tetra-azaocta-1,3,5,7-tetraene-1,1,8,8-tetracarboxylate [C16H24N6O8] from bis(dimethylamino)acetylene and dimethyl diazomalonate

Abstract

Ynediamine (I) reacts with two equivalents of dimethyl diazomalonate thereby forming unexpectedly the ester (III). Its structure was established by X-ray analysis: M= 428.40, orthorhombic, P2₁2₁2₁, a= 20.448(6), b= 12.657(5), c= 8.339(4)ÅZ= 4. D_x= 1.32 g cm^–3, Mo-K_α, λ= 0.710 69 Å, µ= 1.15 cm^–1, F(000)= 904, T 291 K, R= 0.067 for 844 observed reflections. Interestingly, both amide azine moieties of (III) are almost perpendicular and no conjugation takes place between them. Diazodibenzoylmethane behaves in the same manner, whereas ethyl diazoacetate (II) forms the expected bis(dimethylamino)pyrazole (IV).