The cyanocarbonyl group: synthesis and crystal structure of an imidazole carbonyl cyanide, C12N5OH17

1-t-Butyl-5-N-(dimethylaminomethylene)aminoimidazole-4-carbonyl cyanide (BUNDAMIC) is the first acyl cyanide to be synthesized from an imidazole-4-carboxylic acid, diethylphosphorocyanidate, and triethylamine and its structure determined by x-ray crystallography. It crystallizes with four molecules in the monoclinic space group C2/m with a = 17.824(2), b = 6.784(2), c = 11.039(2) Å, and = 96.17(1)°; R = 0.036 over 1086 unique x-ray reflections. The cyanocarbonyl group is nearly linear, C-C N angle 174.4(3)°, with dimensions C N, 1.137(3); C-C 1.493(3); and C=O N 1.224(3) Å. The imidazole ring, in the mirror plane, has a lengthened C4 = C5 bond of 1.421(3) A, and there is a short ring-closing approach, H O6 =2.07 Å, between the methyleneamino hydrogen and the carbonyl oxygen.