Table 1.

Optimization of the Reaction Conditions^a

entry	acid / base	oxidant	atmosphere	solvent	yieldb
1	KHCO3	DMBQ	air	HFIP	(59)
2	KHCO3	benzoquinone	air	HFIP	(34)
3	KHCO3	dimethoxybenzoquinone	air	HFIP	(7)
4	AcOH	DMBQ	air	HFIP	n.d.
5c	KHCO3	DMBQ	air	HFIP	(40)
6	K2HPO4	DMBQ	air	HFIP	(42)
7	iPr2NEt	DMBQ	air	HFIP	(30)
8	KHCO3	DMBQ	air	tAmylOH	(10)
9	KHCO3	DMBQ	air	DMF	(5)
10	KHCO3	DMBQ	air	dioxane	(10)
11d	KHCO3	DMBQ	air	HFIP	(12)
12e	KHCO3	DMBQ	air	HFIP	(14)
13f	KHCO3	DMBQ	air	HFIP	(23)
14	KHCO3	DMBQ	N2	HFIP	n.d.
15	KHCO3	DMBQ	O2	HFIP	65
16	KHCO3	DMBQ (0.5 equiv)	O2	HFIP	50
17	KHCO3	DMBQ (2.0 equiv)	O2	HFIP	80
18	KHCO3	DMBQ (3.0 equiv)	O2	HFIP	73

^aReaction conditions: 1a (0.1 mmol), 2a (1.5 equiv), Pd(OAc)₂ (10 mol %), oxidant (1.5 equiv), base (1 equiv), solvent (0.2 mL), 100 °C, 12–16 h.

^bIsolated yield. Values in parentheses represent yields determined by ¹H NMR analysis of the crude reaction mixture using 1,3,5-triisopropylbenzene as internal standard.

^cKHCO₃ (0.5 equiv).

^d120 °C.

^e80 °C.

^f4Å molecular sieves as additive.