Crystal structure of 2-isopropyl-3,3,7-trimethyl-4-(m-toluidino)-1,2,3,4-tetrahydroquinoline.

reactions of peroxidized chemiluminescent compounds, 5arylamino-1,2,4-trioxanes 4 (Fig. 1).1 The 1,2,4-trioxanes were synthesized by autoxidation of the imines, 3, in the presence of isobutylaldehyde. The crystal structure of this curious compound had already been determined by X-ray diffraction. We continued to investigate the reaction and found that the reaction patterns in the absence of oxygen differed from those in the presence of oxygen. Similar reactions of unhindered anilines in the absence of oxygen proceeded the usual Doebner reaction (DM reaction) to give tetrahydroquinoline derivatives.2 Imines formed from m-toluidine coupled together to give dimers, 5, which cyclized to give the title compounds 6 (55%).3 Since the expected structure holds two asymmetric carbons between a quaternary carbon, we can not assign the precise relative stereochemistry using the usual spectroscopy. In order to confirm the structure of the products and to understand the detailed stereochemistry unequivocally, the crystal structure of the compound was determined. Single crystals of 6 were obtained from hexane. The final results of the refinement and the atomic coordinates are given in Tables 1 and 2, respectively. An ORTEP drawing of 6 is shown in Fig. 2. The essential bond distances and angles of the quinoline ring part are listed in 359 ANALYTICAL SCIENCES FEBRUARY 2001, VOL. 17 2001 © The Japan Society for Analytical Chemistry