Table 1.

Epoxidation of 3-Siloxypropanal with the Aluminum Catalysts^a

entry	ligand	R	R1	catalyst (x mol %)	Me2SO (2x mol %)	epoxide	% yield epoxideb	% ee epoxidec
1	(S)-VANOL	TBS	Bn	5	0	11	66	80
2	(S)-VANOL	TBS	Bn	10	0	13	63	83
3	(S)-VANOL	TBS	Bn	10	20	13	64	81
4	(S)-VANOL	TBS	Bn	5	0	11	85	91
5	(S)-VANOL	TBS	Bn	10	0	11	80	95
6	(S)-VANOL	TBS	PMB	5	0	13	76d	92d
7	(R)-VANOL	TBS	PMB	10	0	13	87e	−95e,f
8	(S)-VANOL	TBDPS	PMB	10	0	14	77	94
9	(S)-BINOL	TBS	Bn	5	0	11	(9)	nd

^aUnless otherwise specified, all reactions were carried out in toluene at 0 °C for 12 h with 0.5 mmol diazo compound 1 at 0.1 M with 1.2 equiv of 2.

^bIsolated yields.

^cDetermined by HPLC.

^dAverage of two runs.

^eAverage of four runs.

^fEnantiomer of epoxide 13 is formed.