Compounds with bridgehead nitrogen. Part 49. The synthesis and stereochemistry of perhydropyrido[3,2,1-j,k][3,l]benzoxazepines and of r-3a,t-11a,c-14a, t-14b, t-22a,t-22b-perhydrodiquino[1,8a,8-c,d:1′,8a′,8′-j,k][1,8,3,10]dioxadiazacyclotetradecine
Abstract
Ring closure of the diastereoisomeric 2-decahydroquinolin-8-ylethanols with formaldehyde gave r-4a,c-7a,t-11a-, r-4a,t-7a,t-11a, and r-4a, c-7a, c-11a-perhydropyrido[3,2,1-j,k][3,1]benzoxazepines, but instead of the fourth isomer a dimer, r-3a,t-11a,c-14a,t-14b,t-22a,t-22b-perhydrodiquino[1,8a,8-c,d:1′,8a′,8′-j,k][1,8,3,10]dioxadiazacyclotetradecine, was obtained. Comparison of 13C n.m.r. shifts of the conformationally locked isomers with those of perhydropyrido[1,2-c][1,3]oxazepine showed different average perhydro-1,3-oxazepine ring conformations in the various structures so that an estimate of the position of conformational equilibrium (CDCl3, solution) of the bicyclic compound from this data could not be made. The 13C n.m.r. spectrum of perhydropyrido[1,2-c][1,3]oxazepine in CDCl3—CFCl3, however, showed a ratio of ca. 5:1 trans-fused: O-inside-cis-fused conformers at –80 °C.