Table 1.

Optimization of (NHC)Pd(II) catalyzed transfer-dehydroaromatization (TDHA)

Entrya	NHC	PdX2	R	Conv. 1 (%)	Yield 2 (%)	2:3	4 (%)
1	L1	PdCl2	R1	64	49	96:4	15
2b			R1	17	5	n.d.	11
3c			R1	16	3	n.d.	13
4			R2	35	<5	n.d.	25
5			R3	< 5	<5	n.d.	<5
6			R4	< 5	<5	n.d.	n.d.
7			-	100	30	34:66	10
8d			R5	53	1	3:97	8
9			R6	6	1	n.d.	4
10			R7	0	0	0	0
11			R8	33	22	71:29	2
12			R9	72	37	92:8	12
13	L2	PdCl2	R1	60	38	88:12	22
14	L3			88	71	91:9	10
15	L4			92	74	96:4	15
16	L5			71	46	92:8	14
17	L6			57	35	98:2	21
18	L7			27	7	98:2	16
19	-			<5	<5	n.d.	<5
20	L4	PdCl2	-	100	25	32:68	29
21e	L1	Pd(TFA)2	R1	90	64	93:7	21
22 f	L1			36	13	91:9	21
23e	L4			65	39	92:8	25

^aStandard condition: substrate 1a (0.25 mmol) and regulator R (0.5 mmol) were added to NHC L/PdCl₂ (0.025 mmol) with HSi(OEt)₃ (0.0375 mmol) in 2 mL THF at r.t. and stirred for 24 hrs. The conversion of 1a and selectivity and yield of product 2a were determined by ¹H NMR.

^bUnder O₂ instead of N₂.

^cNo HSi(OEt)₃.

^d~50% benzene based on R5.

^eHBpin was used instead of silane.

^fNo HBpin or silane was used.

n.d. not determined.