Isoxazole Strategy for the Synthesis of α-Aminopyrrole Derivatives.

The synthesis of methyl 5-aminopyrrole-3-carboxylates from 4-methyleneisoxazol-5-ones via "cyanide Michael addition/methylation/reductive isoxazole-pyrrole transformation" is developed. The last step occurs in a domino mode involving Mo(CO)-mediated reductive isoxazole ring-opening, Mo(CO)-catalyzed --isomerization of the enamine intermediate followed by 1,5-- cyclization. 5-Amino-1-pyrrolo-3-carboxylates react with 1,3-diketones, affording pyrrolo[1,2-]pyrimidine-7-carboxylates, and are easily converted into 2-diazo-2-pyrrole-4-carboxylates. These compounds demonstrate the reactivity of both diazo compounds, giving pyrrole-containing products of intra/intermolecular azo coupling, and carbenes to give pyrrole-containing insertion products into CH and OH bonds under photolysis.