Optimization of the reaction conditions^a.

Entry	NaBH4c (equiv.)	Time (h)	R1	Yieldb (%)
1	0.6	12	Etd	n.d.
2	1.2	12	Etd	n.d.
3	2.0	12	Etd	48
4	3.0	12	Etd	85
5	3.0	6	Etd	89
6	3.0	4	Et d	87
7	3.0	3	Etd	73
8	3.0	4	Ete	11
9	3.0	4	Etf	83
10	3.0	4	Hg	n.d.
11	3.0	4	Hh	73
12	3.0	4	Mei	75
13	3.0	4	Etj	n.d.

^aStandard reaction conditions: 2-oxazolidinone 1a (1.0 mmol), diphenyl diselenide (1.2 equiv., 0.60 mmol), NaBH₄, THF (7.0 mL) and R¹OH (0.6 mL) under reflux and nitrogen atmosphere.

^bIsolated yields.

^cRegarding the limiting agent, 1a.

^d95% ethanol.

^eAbsolute ethanol was used instead of 95% ethanol.

^f0.55 mL of absolute ethanol + 0.05 mL of distilled water.

^g0.6 mL of distilled water was used.

^h0.1 mL of distilled water was used.

ⁱ95% methanol.

^jTHF was omitted and 7.6 mL of 95% EtOH was employed. n.d. = not determined.