Separation of organic bases by Craig distribution. II. Constellation of diastereomeric N,N'-dibutyl-alpha ,alpha '-diphenylethylenediamines

Abstract

cf. CA 54, 21642d. Dimerizing redn. of N-benzylidenebutylamine with Al amalgam gave a mixt. of meso-(I)and dl-N,N'-dibutyl-alpha ,alpha '-diphen- ylethylenediamine (II) which were isolated by Craig distribution (Schoenenberger, CA 52, 18274h). The constellations of I and II were detd. by reaction with CH2O to form imidazolines and measurement of the rate of hydrolysis, by reaction with CS2 at room temp., and by infrared spectroscopy. The mixt. of the diastereomeric I and II was prepd. according to Thies and S. (CA 51, 14580g). The mixt. of I and II (5 g.) and 0.65 paraformaldehyde were dissolved in 20 ml. C6H6, the mixt. refluxed 1 hr., C6H6 together with the H2O formed distd., and the residue (a) recrystd. from Bu2O to obtain 86% dl-threo-1,3-dibutyl-4,5-diphenylimidazoline (III), m. 74 Deg, or (b) distd. in vacuo to obtain erythro-I, b0.6 118-20 Deg. The formed imidazolines (3.3 g.) were each hydrolyzed with 20 ml. H2SO4 in 150 ml. H2O in a steam-distn. app. The steam evolution and the vol. of liquid were kept const. by regulation of the heating. CH2O formed was collected in a well-cooled receiver, first in fractions of 20, later 40-60 ml. The distillate was neutralized with 0.5N HCl (thymolphthalein) and the CH2O contents detd. after addn. of Na2SO3 by titration with 0.5N HCl. The results are given in a graph. I (3.2 g.) in 10 ml. CS2 was kept at room temp. 2 days and the crystals formed filtered off, washed with Et2O, and dried (desiccator) to obtain 63% N-dithiocarboxy deriv. of I, m. 119 Deg, v N-H 3328 cm.-1, S-H 2585 cm.-1, which lost CS2 stored at room temp. to form the dithiocarbamate of I. II (3.2 g.) in 10 ml. CS2 was kept 24 hrs. at room temp., CS2 evapd., and the product distd. in vacuo to obtain 50% 1,3-dibutyl-4,5-diphenylimidazoline-2-thione, yellow oil, b0.5 206 Deg. Infrared spectra of I and II are given.