Table 1. Optimization of the reaction conditions^a.

Entry	Solvent	Yieldb (%)
1 c	CH 3 CN	95
2	CH3OH	87
3	EtOAc	62
4	Acetone	75
5	THF	18
6	Cyclohexane	22
7	DMSO	Trace
8	DMF	21
9	Toluene	24
10	CH2Cl2	n.d.
11	CH3CN/H2O (4/1)	72
12	CH3CN/H2O (1/4)	16

^aReaction conditions: 1a (0.3 mmol) in solvent (15 mL) with γ-ray radiation (dose rate: 110 Gy min⁻¹, measured using a Fricke dosimeter) at room temperature and under an air atmosphere for 15 h.

^bDetermined by gas chromatography-mass spectrometry (GC-MS) using 1,3,5-trimethoxybenzene as the internal standard.

^cThe optimized reaction condition. n.d. = no detected.