Heterocyclic ring-analogs of dihydropyridine calcium antagonists

An improved synthesis of the 1,4-dihydropyrazine derivative, 3, is described that involves the versatile 1,4-diketointermediate, 9. This intermediate was converted to several heterocyclic ring-analogs of 1,4-dihydropyridine in addition to 3 including derivatives of pyrrole and furan.