The tetramer of HCN. Useful precursor of various heterocycles, e.g. imidazoles: Synthesis, 767 (1988); J. Org. Chem., 39, 2341 (1974), pyrazines: J. Org. Chem., 39, 2341 (1974); 44, 827, 4871 (1979); J. Heterocycl. Chem., 11, 79 (1974); Heterocycles, 16, 1449 (1981), pteridines: J. Heterocycl. Chem., 23, 1299 (1986). For extension to synthesis of nucleosides, see: J. Org. Chem., 50, 747 (1985). For a review, with particular reference to its utility in heterocyclic synthesis, see: Tetrahedron, 59, 2749 (2003).
