Table 2.

Epoxidation of Aromatic Aldehydes with VANOL and VAPOL Aluminum Catalysts^a

aldehyde	epoxide	Ligand	catalyst (mol%)	R1	% yield epoxideb	%ee epoxidec
		(S)-VAPOL	5	Bn	97	−99d
		(S)-VAPOL	5	n-Bu	86	−97d
		(S)-VAPOL	10	Bn	84	−99d
		(S)-VANOL	10	Bn	89	−81d
		(S)-VANOL	10	n-Bu	19e,f	nd
		(S)-VANOL	5	n-Bu	86g	93
		(S)-VAPOL	5	Bn	93	−99d
		(S)-VAPOL	5	Bn	76	−99d
		(S)-VAPOL	5	n-Bu	66	−93d
		(S)-VAPOL	10	Bn	11e,h	nd
		(S)-VAPOL	5	Bn	90	99d
		(S)-VAPOL	5	n-Bu	77	−85d
		(S)-VAPOL	5	Bn	55	−62d
		(S)-VAPOL	5	n- Bu	36	−71d
		(R)-VAPOL	10	Bn	70	93

^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 aldehyde. The catalyst was prepared as indicated in Table 1.

^bIsolated yields.

^cDetermined by HPLC. nd = not determined.

^dThe enantiomer of the epoxide was formed.

^eNMR yield.

^fThis reaction as carried out at −40 °C for 12 h.

^gThis reaction was with the boron catalyst prepared as in Scheme 2 without DMSO and was performed at −40 °C for 2 h. See ref 1.

^hReaction went to 50% conversion and also gave a 10% yield of a β-keto amide.