Table 2.

Optimisation studies^a.

Entry	Catalyst	Ligand	Base	Yield 20b(%)
1	Pd(PPh3)4	–	K2CO3	58
2	Pd(PPh3)4	–	Na2CO3	90
3	Pd(PPh3)4	–	KOt-Bu	35c
4	Pd(PPh3)4	P(o-furyl)3	Na2CO3	75
5	Pd(PPh3)4	dppe	Na2CO3	79
6	Pd2dba3.CHCl3	–	Na2CO3	83
7	Pd2dba3.CHCl3	P(o-furyl)3	Na2CO3	80
8	Pd2dba3.CHCl3	dppe	Na2CO3	76
9	Pd(PPh3)4	–	Na2CO3	58d
10	Pd(PPh3)4	–	Na2CO3	82e
11	Pd(PPh3)4	–	Na2CO3	38f
12	–	–	Na2CO3	69

^aReaction conditions: 19a (1.0 equiv), 2a (1.1 equiv), catalyst (5 mol %), ligand (10 mol %), base (2.0 equiv), dioxane (2 mL), 50 °C, 10 h. ^bIsolated yield. ^cDimerization product 4 was formed in 23% yield. ^dCH₃CN instead of dioxane. ^eTHF instead of dioxane. ^frt, 24 h.