Substitution in Fischers Bases

Sulfonation of Fischer s base in 30% oleum gives a 97% yield of the 5- and not the 6-substituted derivative, according to NMR spectral evidence. The compound was used to prepare cyanine and styryl dyes, but no spiropyrans were reported.44 

Fischer s aldehydes having a 2-hydroxyethyl or 2-chloroethyl substituent on the N atom and a 5-nitro substituent were prepared by formylation of the corresponding 

3- trimethylindolinc 1,2 -A oxazines. According to the NMR and IR spectral evidence, the aldehydes, both in solution and the solid state, existed entirely in the open chain form rather than as 2-formylmethyl-2,3,-dimethylindolino[l,2-6]ox- 

Alkylation of Fischer s base generally occurs on the methylene group. Reaction witha-iodoacetamide gave a 26% yield of the spiro product, 5 -oxo-l,3,3-trimethyl- 

3- dihydrospiro-[2ff-indole-2,2 -pyrrolidine] (39). Treatment with perchloric acid opened the pyrrolidone ring and gave in 80% yield the Fischer s base salt having a 2-(2-carbamoylethyl) substituent (40). No information is given as to whether the spiro compound is photochromic, or whether the Fischer s base salt can be further condensed with salicylaldehydes.48 

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