Ring Transformations of Heterocyclic Compounds. XIX Spiro[dihydropyridine-indolines] - Novel Heterocycles with Two Spiro-Condensed N-Containing Subunits Easy Accessible by 1,3-Oxazinium Ring Transformation

The synthesis of hitherto unknown 1-benzoyl-1´,3´,3´-trimethyl-4,6-diphenylspiro[1,2-dihydropyridine-2,2´-indolines] 5 from 2,4,6-triphenyl-1,3-oxazinium tetrafluoroborate (1b) and 1,3,3-trimethyl-2-methylene-indolines 2 (used as such or generated in situ from the corresponding 3H-indolium salts 4) in the presence of triethylamine in anhydrous acetonitrile by a 3,6-[C3N+C2] 1,3-oxazinium ring transformation is reported. Structure elucidation is performed by an X-ray structure determination of the spiro[dihydropyridine-indoline] 5a. Spectroscopic data of the transformation products and their mode of formation are discussed.