Table 1. Boron Enolate Mannich Reactions^a.

entry	boron	catalyst	solvent	yield of 4 [%]b	yield of 5 [%]b
1	1a	-	CH2Cl2	8	-
2	1b	-	CH2Cl2	10	-
3	1c	-	CH2Cl2	<5	-
4	1d	-	CH2Cl2	-	-
5	1e	-	CH2Cl2	5	-
6	1f	-	CH2Cl2	22	<5
7	1f	Cu(NCCH3)4PF6	CH2Cl2	12	37
8	1f	CuOTf	CH2Cl2	13	55
9	1f	Cu(OTf)2	CH2Cl2	<5	76
10	1f	Cu(OTf)2	PhCH3	13	44
11	1f	Cu(OTf)2	THF	6	20

^aReactions were run with 1.0 mmol boronate 1, 1.0 mmol diazo ester 2, 1.0 mmol acyl imine 3a, in CH₂Cl₂ (0.2 M) for 12 h under Ar, followed by flash chromatography on silica gel.

^bIsolated yield.