Table 2.

Retro-[4+2]/[4+2] reactions to afford bicyclo[2.2.2]-octenones^a

entry	dienophile (equiv)	cycloadductb	yieldc (%)
1	9a	10a	85
2	9b	10b	99
3	9c	10cd	98
4	9d	10d	85
5	9e	10ed	76
6	9f	10f	90
7	9g	10gd	80

^aReaction conditions: dimer (−)-2, dienophile, SiC chip, mesitylene, μW, 180 °C, 15 min;

^bSingle diastereomer isolated unless otherwise noted;

^cIsolated yield after column chromatography;

^dApproximately 9% of an inseparable minor product observed by ¹H-NMR (ca. 10:1 isomeric ratio).