Facile syntheses of oxazolines and thiazolines with N-acylbenzotriazoles under microwave irradiation

Microwave reactions of 2-amino-2-methyl-1-propanol (2) or 2-aminoethanethiol hydrochloride (4) with readily available N-acylbenzotriazoles 1a-j in the presence of SOCl(2) produced 2-substituted 2-oxazolines 3a-j in 84-98% yields and 2-substituted thiazolines 5a-i in 85-97% yields, respectively. With use of this method chiral oxazoline 6, bisoxazoline 7, bisthiazoline 8, and 5,6-dihydro-4H-1,3-oxazines 9 or 10 have also been prepared in 82-96% yields. These results demonstrate a new application of N-acylbenzotriazoles in the preparation of oxazolines and thiazolines under mild conditions and short reaction times with microwave irradiation.