Reactions of tosyl azide with 2-phenoxy- and 2-phenylsulfanyl-2,3-dihydro-1H-indane-1,3-dione. Unexpected reactivity of intermediate 4-acyl-5-hydroxy-1-tosyltriazolines

Abstract

The reaction of tosyl azide 1 with 2-phenoxy-2,3-dihydro-1H-indane-1,3-dione 2c, carried out in hexamethyl-phosphoramide (HMPA) or in diethyl ether in the presence of triethylamine, fails to afford the expected diazo transfer product, i.e. the diazoacetophenone 3c(3c′), but instead leads to the dimeric indanedione 7 the formation of which is primarily ascribable to preferential fragmentation of the transient hydroxytriazoline 4c to give zwitterion 9c and dinitrogen. Under comparable conditions, tosyl azide 1 and 2-phenylsulfanyl-2,3-dihydro-1H-indane-1,3-dione 2d in HMPA gives the ring-expanded hydroxybenzopyran 15, the formation of which is similarly ascribed to preferential fragmentation of the corresponding 4,5-dihydro-1H-triazole 4d to give zwitterion 9d. However, analogous reaction of the dione 2d in THF, in the presence of triethylamine, affords 2-diazo-2,3-dihydro-1H-indane-1,3-dione along with diphenyl disulfide, toluene-p-sulfonamide and phenyl toluene-4-thiosulfonate. These latter products are believed to arise from ready decomposition of the 4,5-dihydro-1H-triazole 4d precursor, i.e. the triazenyl union 13. X-Ray crystal structure analyses of compound 7 and the acetoxybenzopyran 17 are also reported.