Efficient synthesis of spiro compounds employing N-alkylisatins or ninhydrin

The 1,3-dipolar intermediates generated by addition of isoquinoline, to dialkylacetylenedicaboxylates are trapped by N-alkylisatins to produce dialkyl 1,2-dihydro-2-oxo-1-alkyl-spiro[3H-indol-3,2'- [2H,11bH][1,3]oxazino[2,3-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 1,3-(2H)- dione-spiro[3H-indene-3,2'-[2H,11bH][1,3]oxazino[2,3-a]isoquinoline]-3',4'-dicarboxylate, dimethyl 1,3-(2H)- dione-spiro[3H-indene-[3H,4aH]-[1,3]oxazino[3,2-a]quinoline]-1,2-dicarboxylate or dimethyl 1,3-(2H)-dionespiro[ 3H-indene-[2H,9aH]-pirido[2,1-b][1,3]oxazino-3,4-dicarboxylate.