The effect of molar ratio of β-keto ester 1a, oxime 2a and t-BuOOH on yields of the reaction products 3a and 4a^a.

Entry	Molar ratio of 1a, 2a and t-BuOOH	Yield of 3ab (%)	Yield of 4ab (%)
1	1 : 1 : 2	61	Trace
2	1 : 1 : 3	70 (64)	Trace
3	1 : 1.5 : 2	81 (77)	n.d.
4	1 : 2 : 2	76	Trace
5	1 : 3 : 2	60	n.d.
6	1 : 3 : 3	57	Trace
7	1.5 : 1 : 2	74	18
8	1.5 : 1 : 3	76	20
9	2 : 1 : 3	51	34

^aGeneral reaction conditions: β-keto ester 1a (1–2 mmol), oxime 2a (1–3 mmol), Cu(BF₄)₂·6H₂O (0.1 mmol, 10 mol%), t-BuOOH (70% aq.) (2–3 mmol), MeCN (5 mL) at 80 °C for 1 h.

^bYields of 3a and 4a were determined based on ¹H NMR using p-methoxyacetophenone as an internal standard; in the entries 2 and 3 isolated yields of 3a based on β-dicarbonyl compound are given in parenthesis. n.d. – not detected.