Sulfonic Acid Functionalized Nano-γ-Al₂O₃: A New, Efficient, and Reusable Catalyst for Synthesis of 3-Substituted-2H-1,4-Benzothiazines

Table 2

Solvent optimization for the synthesis of 3-phenyl-2H-1,4-benzothiazine^a.

Entry	Solvent	Temperature/°C	Time/h	Yield/%^b
1	H2O	Reflux	24	12
2	CH3CN	Reflux	3	97
3	CH2Cl2	Reflux	8	85
4	THF	Reflux	6	88
5	EtOH	25	10	69
6	EtOH	40	8	75
7	EtOH	60	5	89
8	EtOH	Reflux	3	96

aReaction conditions: o-aminothiophenol (1 mmol), 2-bromo-1-phenyl-ethanone (1 mmol); sulfonic acid functionalized nano-γ-Al₂O₃ (50 mg); reflux.
bIsolated yield.