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

Table 3

Preparation of 3-substituted-2H-1,4-benzothiazines^a.

Entry	R^1	R^2	Time/h	Product	Yield/%^b
1	H	C6H5	3	3a	96
2	H	4-Me-C6H4	2	3b	97
3	H	4-MeO-C6H4	2	3c	95
4	H	4-F-C6H4	4	3d	93
5	H	4-Cl-C6H4	4	3e	94
6	H	4-Br-C6H4	4	3f	90
7	H	4-NO2-C6H4	6	3g	89
8	H	2-MeO-C6H4	3	3h	90
9	H	3-NO2-C6H4	6	3i	88
10	H	3,4,5-(MeO)3-C6H2	6	3j	86
11	H	2-Benzofuryl	5	3k	91
12	Cl	CH3	10	3l	78
13	Cl	C6H5	3	3m	93
14	Cl	4-Me-C6H4	3	3n	95
15	Cl	4-MeO-C6H4	3	3o	93
16	Cl	4-Cl-C6H4	4	3p	90
17	Cl	4-Br-C6H4	4	3q	87
18	Cl	2-Benzofuryl	4	3r	88
19	CF3	C6H5	4	3s	86
20	CF3	4-MeO-C6H4	4	3t	89

aReaction conditions: o-aminothiophenol (1 mmol), ω-bromoketones (1 mmol); sulfonic acid functionalized nano-γ-Al₂O₃ (50 mg); EtOH (10 mL); reflux.
bIsolated yield.