Reactions of Fischer's base with cyclic and acyclic conjugated nitroolefins and nitrovinylethers

The reactions of 2,3-dihydro-2-methylene-1,3,3-trimethyl-1 H-indole (Fischer’s base) with nitro-olefins and alkoxy- nitro-olefins have been examined. Formation of the corresponding Michael-type adducts has been observed in all cases with the exception of 2-nitropropene for which the spiro- 1,2-oxazine N-oxide derivative could be isolated. The Michael-ty pe adducts derived from alkoxy- nitro-olefins underwent a rapid elimination reaction resulting in the eventual formal nitro-olefination of the Fischer’s base. The geometry of the products has been determined by means of DIFNOE experiments and their UV properties have been examined.