N-Aryl Lactams by Regioselective Ozonation of N-Aryl Cyclic Amines

Table 1

Conversion and isolated yields in 4-(4-nitrophenyl)-morpholin-3-one (4) after ozonation of 4-(4-nitrophenyl)-morpholine (3) at different experimental conditions (DCM: dichloromethane, CAN: acetonitrile, EA: ethyl acetate).

Entry	𝑇 (°C)	𝑡 (h)	Solvent	Ozone^a	Conversion^b (%)	4 (%)^c	Other
1	25	1.5	ACN	excess	100	18	𝟔,𝟕,𝟖
2	0	1	ACN	excess	100	35	𝟔,𝟕,𝟖
3	0	3	ACN	2 : 1	100	54	𝟕,𝟖
4	0	3	ACN	1 : 10	11	8	—
5	0	3	DCM	2 : 1	91	29	𝟕,𝟖
6	0	3	n-Hexane	2 : 1	80	24	𝟔,𝟖
7	0	3	Acetone	2 : 1	100	52	𝟔,𝟕,𝟖
8	0	3	EA	2 : 1	98	34	7
9	5	0.5	Water PH = 7	excess	87	2	—
10	5	3	Water pH = 3	8 : 1	74	1	—
11	5	3	Water pH = 12	8 : 1	81	0	—
12	5	3	n-Butanol	6 : 1	72	2	—
13	0	3	ACN	none	2	0	—
15^d	0	0.5	ACN	1 : 40	74	56	𝟕,𝟖

^a100 mg of 4-(4-nitrophenyl)-morpholine (3) were dissolved in 50 mL of solvent and ozonized at the selected temperature for the selected time. When the reactions were carried out with a limited amount of ozone, 30 mg 4-(4-nitrophenyl)morpholine (3) were dissolved in the required amount of solvent. Ozone concentrations were estimated on the basis of the iodometric method [25].
^bConversions are calculated on the recovered 4-(4-nitrophenyl)morpholine.
^cGC-MS yield.
^dFor the conditions see the experimental section.