Optimization studies for the annulation of allylidenemalononitril 1a and VEC 2a^a.

Entry	Catalyst	Solvent	Temp. (°C)	Yieldb (%)	3a : 4ac
1d	Pd(PPh3)4	Toluene	20	72	3.5 : 1
2 e	Pd(PPh 3 ) 4	MeCN	20	96(90)	>20 : 1
3d	Pd(PPh3)4	DCM	20	68	3.6 : 1
4d	Pd(PPh3)4	CHCl3	20	85	2.6 : 1
5	Pd(PPh3)4	THF	20	85	1.4 : 1
6e	Pd(PPh3)4	DMF	20	16	>20 : 1
7f	Pd/L1–L7	THF	20	<5	—
8	Pd(PPh3)4	THF	40	98	1 : 4.6
9	Pd(PPh 3 ) 4	THF	60	91(84)	<1 : 20
10	Pd(PPh3)4	THF	80	89	<1 : 20
11	Pd(PPh3)4	1,4-Dioxane	60	83	16.0 : 1
12	Pd(PPh3)4	Toluene	60	88	1 : 1.3
13	Pd(PPh3)4	MeCN	60	87	8.6 : 1
14	Pd(PPh3)4	DMF	60	81	14.8 : 1
15	Pd(PPh3)4	DCM	60	76	1 : 1.4
16	Pd(PPh3)4	CHCl3	60	80	5.3 : 1

^aUnless noted otherwise, the reactions were carried out with 1a (0.10 mmol), 2a (0.15 mmol) and the Pd catalyst (5 mol%) in solvent (1 mL) for 12 h.

^bYield was determined by ¹H-NMR analysis with CH₂Br₂ as the internal standard; the data in parentheses refer to isolated yields.

^cThe ratio of 3a : 4a was determined by ¹H-NMR analysis of the crude reaction mixture.

^dFor 48 h.

^eFor 24 h.

^fThe Pd/ligand complex was pre-prepared with Pd₂(dba)₃·CHCl₃ and a ligand in THF at rt for 1 h.