Reaction optimization studies with phenylboronic acid.^a,b.

Entry	Solvent	Additive	Temp (°C)	Time (h)	Yieldb (%)
1	CH3CN	—	30	12	n.r.
2	CH3CN	—	80	12	—c
3	ClCH2CH2Cl	—	80	6	—c
4	ClCH2CH2C–H2O	—	80	6	40
5	ClCH2CH2Cl–H2O	K2CO3 (0.25 mmol)	80	6	57
6	ClCH2CH2Cl–H2O	K2CO3 (0.50 mmol)	80	6	66
7	ClCH2CH2C–H2O	K2CO3 (0.75 mmol)	80	6	67
8	H2O	K2CO3 (0.50 mmol)	80	2	80
9d	H2O	K2CO3 (0.50 mmol)	80	6	n.r.

^aReaction conditions: a mixture of 1a (0.5 mmol), 4a (0.75 mmol) and K₂S₂O₈ (1.0 mmol) in solvent was stirred as mentioned in the table above.

^bIsolated yield. n.r.: no reaction.

^cProduct 3aa could not be isolated.

^dReaction was performed without K₂S₂O₈.