Reaction of N-Heterocycles with Acetylenedicarboxylates in the Presence of N-Alkylisatins or Ninhydrin. Efficient Synthesis of Spiro Compounds

Summary. The 1,3-dipolar intermediates generated by addition of isoquinoline, to dialkyl acetylenedicaboxylates are trapped by N-alkylisatins to produce dialkyl 1,2-dihydro-2-oxo-1-alkylspiro3H-indol-3,2′-2H,11bH]1,3]oxazino2,3-a]isoquinoline]-3′,4′-dicarboxylates in excellent yields. The reaction of isoquinoline, quinoline, or pyridine with dimethyl acetylenedicarboxylate in the presence of ninhydrin led to dimethyl 1,2-dihydro-1,3-dioxospiro3H-indene-3,2′-2H,11bH]1,3]oxazino2,3-a]isoquinoline]-3′,4′-dicarboxylate, dimethyl 1,2-dihydro-1,3-dioxospiro3H-indene-3,3′3H,4aH]1,3]oxazino3,2-a]quinoline]-1,2-dicarboxylate, or dimethyl 1,2-dihydro-1,3-dioxospiro3H-indene-3,2′-2H,9aH]pyrido2,1-b]1,3]oxazino]-3,4-dicarboxylate.