Table 3.

Scope of α-sulfenylation of trisubstituted piperazine-2,5-diones with reagent 2b and 10 mol % of cinchona alkaloids 4a–4c.

entry	substrate	R1	R2	R3	solvent	temp, °C	catalyst	eq. of 2b	time, h	product	yield,a %
1	1f	Me	Me	Me	PhH/PhMe (3:1)	−10	4c	3.0	18	3f	99
2	1a	Me	Me	Et	PhH/PhMe (3:1)	−10	4c	3.0	30	3k	99
3	1g	Me	Me	t-Bu	PhH/PhMe (3:1)	−10	4c	3.0	48	3g	96
4	1h	Et	Et	Et	Toluene	rt	4c	3.0	60	3h	77
5	1h	Et	Et	Et	Toluene	rt	4cb	8.0	48	3h	94
6	1i	Bn	Bn	Et	Toluene	rt	4c	3.0	60	3i	75
7	1i	Bn	Bn	Et	Toluene	rt	4cb	8.0	48	3i	95
8	1b	H	Me	Et	Toluene	rt	4c	3.0	16	3l	81
9	1j	Bn	Bn	t-Bu	Toluene	rt	4cb	10.0	72	3j	52
10	1j	Bn	Bn	t-Bu	Toluene	rt	4a	2.0	60	3j	5
11	1j	Bn	Bn	t-Bu	Toluene	rt	4b	2.0	60	3j	5

^aYield of purified product after chromatographic separation.

^b20 mol% catalyst used.