Angewandte Chemie International Edition

New structural motives for organosuperbases, that are easy to prepare and highly basic are urgently required in many areas of chemistry. The synthesis of N, N’-bis(imidazolyl)guanidine bases (BIG bases) is reported. Their pKa values are determined as 26.1–29.3 in THF. They are thus probably the strongest phosphorous-free organic bases both in solution and in the gas phase. Calculations help to determining the structural and electronic factors giving rise to the high basicity.