FORMATION OF SPIRO-LACTOLS UPON REACTION OF NINHYDRIN WITH METHYLDIAZINES

Reaction of ninhydrin (4) with 4-methylpyridazine or 4-methylquinoline leads to 2-hydroxy-2-heteroarylmethyl-1,3-indandiones (5), which resi st dehydration to the corresponding 2-heteroarylmethylene-1,3-indandio nes (2). In contrast, employing methyl(di)azines with a methyl group i n alpha-position to a ring nitrogen atom (3-methylpyridazine, 4-methyl pyrimidine, 2-methylpyrazine, 2-methylquinoline, 2-methylquinoxaline) results in the exclusive formation of novel l-3a',8b'-dihydrospiro[ind ane-2,2'(3'H)-4'H-indeno [1,2-b]furan]-1,3,4'-triones (7) which might result from cyclisation of initially formed -2,2'-(heteroarylmethylene )bis-1,3-indandiones(6).