“…The fusion of mesityl oxide and aniline using an iodine catalyst (91) and subsequent addition of acid yields 65% of 2,2,4-trimethyldihydroquinoline (CIII) by a Type 3a condensation. The acid-catalyzed reaction of mesityl oxide and o-phenylenediamine (44) was originally thought to give a 1,4-dihydroquinoxaline. This material has now been proved (122) to be 2isobutenyl-2-methylbenzimidazoline (CIV), formed in a Type 1 reaction.…”