2,3,5,6-tetramethylmorpholine. V. Mechanism study of cyclization of 3,3′-iminobis-2-butanols

The mechanism of cyclization of 3,3′-iminobis-2-butanols to 2,3,5,6-tetramethylmorpholines in sulfuric acid is studied. Contrary to our prior suggestions, the ring closure seems to be exclusively a normal S-type substitution. The partial inversion before the cyclization is discussed.