DA reaction between cyclopentadiene 5 and various dienophiles.

Entrya	5	t (h)	Conv.b (%)	10 yieldc (%)	endo : exod
1	5a	1	100	90	86 : 14
2e	5a	1	—	—	—
3	5b	1	100	Quant	86 : 14
4e	5b	1	9	—	—
5e	5b	3	33	27	77 : 23
6	5c	1	100	Quant	2 : 98
7	5d	4	94	90	69 : 25
		16	100	96	77 : 23
8	5e	4	78	72	84 : 16
		16	95	91	84 : 16
9	5f	4	54	50	91 : 9
		16	72	68	89 : 11
10	5g	4	37	34	84 : 16
		16	61	60	80 : 20
11	5h	2	Quant	93	>99 : 1

^aReaction conditions: 9 (0.45 M), 5 (0.15 M), C₆ and TrCl (0.039 M.) in 1.1 mL of water-saturated CDCl₃, at rt.

^bDetermined by ¹H NMR analysis of the crude reaction mixture.

^cIsolated yield.

^dDetermined by ¹H NMR analysis of the crude reaction mixture according to literature data.^21b,21d,27

^eThe reaction was performed in the absence of C₆ and TrCl.