Reaction Steps
2,4,6-Trimethylphenyl isocyanate (Lancaster Co., 20.5 g, 0.127 mol) and 2,4,6-trimethylaniline (17.2 g, 0.127 mol) were reacted in a procedure analogous to that described in Example 1, giving a brown solution. A thick, white flaky precipitate was observed to form about 2 hours after aniline addition. This material was collected by filtration, rinsed with hexanes, and dried in vacuo (crop 1). The CHCl3 reaction filtrate (also containing rinse hexanes) was set aside and was observed to produce additional white precipitate overnight. It was concentrated somewhat using a rotary evaporator and insolubles were similarly collected by filtration, rinsed with hexanes until a pinkish impurity was removed, and dried (crop 2). Three additional crops of material were collected in this fashion. Crop 3 was collected by removal of volatiles from the filtrate of crop 2, crushing the resultant solid, slurrying it in hexanes overnight, and collecting insolubles by filtration and rinsing them with hexanes. Crop 4 was collected by removal of volatiles from the filtrate of crop 3, slurrying with petroleum ether, and collecting insolubles by filtration and rinsing them with petroleum ether. Crop 5 was collected identically by treatment of the filtrate from Crop 4, using smaller slurry and rinse volumes of petroleum ether. The weights of crops 1 to 5 were 11.1 g, 8.32 g, 5.96 g, 2.30 g, and 4.19 g, respectively (total 31.9 g, 84.6%). 1H NMR (solid state CRAMPS, 500 MHz): δ 7.5 (br, aryl), 6.1 and 5.1 (NH), 1.4, 0.9 (sh), and 0.5 (sh) (overlapping, CH3). 13C{1H} NMR (solid state CPMAS, 50 MHz): δ 157.9 and 154.9 (br, C=0, 1 C), 135.0, 129.6, 128.7, and 127.6 (aryl, 12 C), 22.8, 20.0, 19.4, and 17.9 (CH3, 6 C). IR (KBr pellet): 3286 (vs), 3003 (w), 2972 (m), 2918 (s), 2855 (w), 1640 (vs), 1609 (s), 1553 (vs), 1485 (m), 1470 (sh), 1446 (sh), 1377 (w), 1308 (w), 1285 (w), 1252 (sh), 1223 (s), 1065 (w), 1032 (w), 1013 (w), 882 (w), 849 (m), 760 (w), 748 (w), 721 (sh), 696 (m), 580 (w) cm−1. FD-MS m/z (%): 296.7 (MH+, 100). Exact mass calculated for C19H24N2O: 296.19. Melting point (DSC): onset (extrapolated) 236° C., max. 240° C.
