Table 3.

O -Nucleophile Substrate Scope^a

Entry	Nucleophile	3% Remainingb	4% Yieldb,c	6% Yieldb,c	erd
1		10	4a, 71 (68)	6a, 15 (15)	96:4
2e		16	4b, 66 (23)	6b, 7 (5)	94:6
3		16	4c, 61 (41)	6c, 13 (5)	93:7
4		90	4d, 0	6d, 0	n/a
5		18	4e, 53 (45)	6e, 20 (3)	92:8
6f		2	4f, 63 (63)	6f, 32 (23)	94:6
7		5	4g, 67 (66)	6g, 21 (17)	97:3
8a		9	4h, 59 (49)	6h, 7 (6)	96:4
8b		14	4i, 64 (56)	6i, 13 (7)	95:5
9		1	4j, 13 (8)	6j, 0	>99:1

^aReported results are the average of two trials. Reaction conditions: 3 (0.2 mmol), nucleophile (1.3 equiv), Cu(MeCN)₄BF₄ (10 mol %), peptide (20 mol %), K₃PO₄ (4.0 equiv), and MeCN (0.8 mL), 45 °C (except for entry 8, which was performed at 60 °C).

^bYield was determined using ¹H NMR by comparing to an internal NMR standard (1,4-bis(trimethylsilyl)benzene).

^cThe numbers in parentheses are isolated yields.

^dEnantiomeric ratios were determined using chiral HPLC analysis.

^eProducts could not be isolated by the typical procedure. The crude mixture was debrominated following procedure 9 to give S12 (see SI). NMR yields were determined before debromination.

^fEntry was run at 60 °C