Optimization of the organocatalytic asymmetric α-selenation of isoxazolidin-5-one 2a^a.

Entry	Cat.	5	Solvent	t [h]	T [°C]	Yieldb [%]	erc
1	A (5%)d	5a	Toluene	20	25	37	62 : 38
2	B (5%)d	5a	Toluene	20	25	48	51 : 49
3	C (5%)d	5a	Toluene	20	25	47	54 : 46
4	D (5%)	5a	Toluene	2	25	81	51 : 49
5	QN (10%)	5a	Toluene	2	25	68	75 : 25
6	QD (10%)	5a	Toluene	2	25	65	32 : 68
7	CD (10%)	5a	Toluene	2	25	65	73 : 27
8	DHQN (10%)	5a	Toluene	2	25	73	76 : 24
9	QN (5%)	5a	Toluene	2	25	43	69 : 31
10	QN (10%)	5a	CH2Cl2	2	25	76	69 : 31
11	QN (10%)	5a	MTBE	2	25	76	61 : 39
12	QN (10%)	5a	Toluene	2	0	82	75 : 25
13	QN (10%)	5a	Toluene	2	−20	76	75 : 25
14	QN (10%)	5a	Toluenee	2	25	78	76 : 24
15	QN (10%)	5b	Toluene	2	25	74	81 : 19
16	DHQN (10%)	5b	Toluenee	2	25	72	83 : 17
17	DHQN (10%)	5b	Toluenee	14	0–25	69(72)f	83 : 17(83 : 17)f

^aUnless otherwise stated, reactions were run using 0.05 mmol 2a and 0.055 mmol 5 in the presence of the given catalyst in the indicated solvent (c = 0.05 M with respect to 2a) under Ar and exclusion of light.

^bIsolated yields.

^cDetermined by HPLC using a chiral stationary phase (given as (+)/(−)-enantiomeric ratio).

^dWith 1.1 equiv. K₂CO₃.

^e c = 0.025 based on 2a.

^f0.8 mmol scale.