Reaction of N ‐benzyl‐1,1′‐iminobis‐2‐butanols with 70% w/w sulfuric acid

Treatment of ( S:R )‐ N ‐benzyl‐1,1′‐iminobis‐2‐butanol with 70% w/w sulfuric acid gives cis ‐ and trans‐N ‐benzyl‐2,6‐diethylmorpholines (15 and 74%, respectively) and N ‐alkenyl‐4‐ethyl‐1,2,3,4‐tetrahydroisoquinolines (5%). Hydrogenation of the reaction mixture gives cis ‐ and trans ‐2,6‐diethylmorpholines and N ‐butyl‐4‐ethyl‐1,2,3,4‐tetrahydroisoquinoline. Neither N ‐benzyl‐ N ‐crotyl‐(2‐hydroxy‐1‐butyl)amine ( 4 ) nor N ‐benzyldicrotylamine ( 5 ) are intermediates in the reaction. ( S:S )‐ N ‐Benzyl‐1,1′‐iminobis‐2‐butanol gives 95% of cis‐N ‐benzyl‐2,6‐diethylmorpholine and 1% of the trans isomer.