A retro-Diels-Alder approach to oxazoles and imidazoles
摘要:
Heating N-acyl derivatives 4 of 3-endo-aminobicyclo[2.2.1]hept-5-en-2-endo-ol (3) at 185-195-degrees-C for 4-5 h provides oxazoles 1a-e in 49-88 % yields. The reaction proceeds via initial dehydration to an oxazoline which undergoes retro-Diels-Alder reaction to provide the oxazole. Similarly, imidazoles 7a-f may be obtained in 40-79 % yields by heating imidazolines 6a-f to effect the cycloreversion.