Synthesis of novel pyrazole-based heterocycles via a copper(II)-catalysed domino annulation.

Pyrazole-based β-aminonitriles and β-amino-carbaldehydes as bifunctional building blocks are introduced in a facile copper(II)-catalysed one-pot domino generation of multiple N-containing heterobi- and tricycles. This streamlined synthetic approach permits easy access to novel pyrazole-fused imidazo- and pyrimido[1,2-c]pyrimidinones and to pyrazolo[3,4-d]pyrimidinone species with isolated yields up to 90%. The present study also reveals a unique amine-isocyanate coupling promotion via copper(II)-based catalytic activation.