Screening of reaction conditions^a.

Entry	Mediator	Solvent	T (°C)	Yieldc (%)
1	MnCl2	CHCl3 : EtOH	30	56(37), NDe
2	MnCl2	CHCl3 : EtOH	60	51(40)
3	MnCl2	CHCl3 : EtOH	80	52(40)
4	MnBr2	CHCl3 : EtOH	30	54(42)
5	MnI2	CHCl3 : EtOH	30	Trace
6	MnCO3	CHCl3 : EtOH	80	NDd
7	Mn(OTf)2	CHCl3 : EtOH	80	NDd
8	Mn(acac)3	CHCl3 : EtOH	80	NDd
9	Mn(OAc)3	CHCl3 : EtOH	80	NDd
10	FeCl3	CHCl3 : EtOH	80	NDd
11	CoCl2	CHCl3 : EtOH	80	NDd
12	NiCl2	CHCl3 : EtOH	80	NDd
13	CuCl2	CHCl3 : EtOH	80	NDd
14	MnCl2	Toluene	80	Trace
15	MnCl2	Chloroform	80	38(35)
16	MnCl2	Ethanol	80	<5(11)
17	MnCl2	THF	80	42(47)
18	MnCl2	Acetonitrile	80	29(34)
19	MnCl2b	CHCl3 : EtOH	30	Trace

^aReaction conditions: BINAP (0.16 mmol), metal-mediator (3.0 eq.). ^aMixed-solvent (V_chloroform : V_EtOH = 2 : 1, 10 mL), under an O₂ atmosphere (1 bar) at corresponding temperature for 5–10 minutes.

^b10 mol%.

^cIsolated yields for helicenes and BINAPOs (in parentheses).

^dND represents not detected.

^eAr instead of O₂.