Table 2.

Tandem retro-DA/DA reactions using bicyclooctenone (−)-3^a

entry	Dienophile(eqiv)	cycloadduct	Time(h)	Yieldb (%)
1	(5 equiv) 9	12c	3	92
2	(20 equiv) 10	13	12	84
3	(10 equiv) 11	14	3	99
4d	(10 equiv) 15	16	4	42
		17	4	39
5	(5 equiv) 18	19	4	98
6	(2.5 equiv) 20	21	5	57

^aReaction conditions: dimer (−)-3, dienophile, mesitylene, 150 °C;

^bIsolated yield after column chromatography;

^cApproximately 6% of an inseparable minor product was observed by ¹H-NMR;

^dAcetylation required for product separation.