Microwave promoted a green protocol for solvent free synthesis of 1,5-benzothiazepine and [1,3,4]-thiadiazepine derivatives incorporating thiophene moiety

Figures & data

short-legendScheme 1. 

Table 1. Synthesis of 2,3-dihydro-1,5-benzothiazepines 5a-c under conventional (reflux) condition and microwave irradiations.

		Conventional		M.W Irrad.
Compound	Ar	Time (h)	Yield^a (%)	Time (min)	Yield^a (%)	M.P. (^OC)
5a	p-F-Ph	10	65	1	85	208-210
5b	p-CN-Ph	12	59	2	82	202-204
5c	2-thienyl	12	61	1.5	89	193-195
^aYield of crude products.

short-legendScheme 2. 

Table 2. Synthesis of 7,8-dihydro[1,2,4]triazolo[3,4-b][1,3,4]thiadiazepines10a-f under microwave irradiations.

			Conventional		M.W. Irrad.
Compound	Ar	R	Time (h)	Yield^a (%)	Time (min)	Yield^a (%)	M.P.(^OC)
10a	p-F-Ph	phenyl	14	73	6	94	195-196
10b	p-CN-Ph	phenyl	16	71	14	91	188-190
10c	2-thienyl	phenyl	15	70	15	90	164-166
10d	p-F-Ph	2-BT	15	70	25	88	80-82
10e	p-CN-Ph	2-BT	18	65	28	86	112-113
10f	2-thienyl	2-BT	18	67	33	83	107-109
^aYield of crude products.

Table 3. Inorganic solid supports effect on time and yield^a in the synthesis of compounds 5a, 10a, 10d.

	Yield (%)			Time (min)
Support	5a	10a	10d	5a	10a	10d
Silica sulfuric acid	85	73	71	1	9	32
Silica gel	60	58	54	60	60	80
Acidic alumina	70	62	61	60	60	80
Basic alumina	not isolated	94	88	90	6	25
Montmorillonite K10	52	51	50	90	60	80
K2CO3	59	80	77	60	25	25
None	40	46	44	11	50	65
^aYield of crude products.

Table 4. The effect of microwave irradiation power on the formation of 5a ^a .

Irradiation power (Watt)	200	400	600	800
Yield%^b	49	58	77	85
^aIrradiation time is 1 min.
^bIsolated yield. Each reaction was repeated three times and the result was averaged.

Table 5. The effect of microwave irradiation time on the formation of 5a ^a .

Irradiation Time (min.)	1	1.5	2	3
Yield%	85	85	80	80
^aIrradiation power is 800 watt.