Synthesis of imidazo[4,5-e]thiazolo[2,3-c]-1,2,4-triazine-2,8-diones via a rearrangement of imidazo[4,5-e]thiazolo[3,2-b]-1,2,4-triazine-2,7-diones in the reaction with isatins

An aldol condensation/skeletal rearrangement protocol for the synthesis of 1,3-dialkyl-7-(2-oxo-1,2-dihydro-3 H -indol-3-ylidene)-1,3 a ,4,9 a -tetrahydroimidazo[4,5- e ]thiazolo[2,3- c ]-1,2,4-triazine-2,8(3 H ,7 H )-diones in good to high yields via a one-pot reaction of 1,3-dialkyl-3,3 a ,9,9 a -tetrahydroimidazo[4,5- e ]thiazolo[3,2- b ]-1,2,4-triazine-2,7(1 H ,6 H )-diones and 1 H -indole-2,3-diones (isatins) or through the generation and rearrangement of 1,3-dialkyl-6-(2-oxo-1,2-dihydro-3 H -indol-3-ylidene)-3,3 a ,9,9 a -tetrahydroimidazo[4,5- e ]thiazolo[3,2- b ]-1,2,4-triazine-2,7(1 H ,6 H )-diones has been developed.