(+)-CSA Catalyzed Multicomponent Synthesis of 1-[(1,3-Thiazol-2-ylamino)methyl]-2-naphthols and Their Ring-Closure Reaction under Ultrasonic Irradiation

Table 1

Screening of catalysts for the three-component reaction of 2-aminothiazole, benzaldehyde, and 2-naphthol.

Catalyst (mol%)	Solvent	Temperature; (°C)	Time; (min)	Yield; (%)
—	—	25	120	65
—	—	50	120	74
VB1 (10)	—	50	60	66
Sc(OTf)3 (10)	—	50	60	70
Bi(OTf)3 (10)	—	50	60	67
Yb(OTf)3 (10)	—	50	60	73
(+)-CSA (10)	—	50	60	87
—	IL1	50	60	32
—	IL2	50	60	34
—	IL3	50	60	40

Isolated yield.
IL1: 1-benzyl-3-methylimidazoliumchloride.
IL2: 1-ethyl-2,3-dimethylimidazoliumtetrafluoroborate.
IL3: 8-ethyl-1,8-diazabicyclo5,4,0-7-undecenium trifluoromethanesulfonate.