Arene-alkene cycloadditions

While the orbital symmetry analysis of the arene-alkene cycloadditions addresses their allowedness , it does not specify a sequence for bond formation. It was recognized, however, that these cycloadditions could proceed stepwise and that in the specific case of the meta cycloaddition, three temporally distinct pathways are possible (Scheme 2) (a) a fully concerted path (A) where all bonds are formed simulta-... 

Finally, steric effects have been observed to play a significant role in controlling the dia-stereoselectivity of the arene-alkene cycloadditions. Elaboration of this aspect of the reaction again rests on an exciplex model and will be provided in the context of synthetic plications where it has been most frequently encountered. 

With the above synthetic considerations as a backdrop, the use of the arene-alkene cycloaddition in complex molecule total synthesis can now be examined. The emphasis here will be on the meta cycloaddition process since it has received the most study. It will become apparent, however, that even this reaction has received relatively little attention in synthesis in spite of its enormous potential. This situation is likely to change riqiidly as recent theoretical and synthetic advances are assimilated. 

Wender, P. A., Ternansky, R., Delong, M., Singh, S., Olivero, A., Rice, K., Arene Alkene Cycloadditions and Organic Synthesis, Pure Appl. Chem. 1990, 62, 1597 1602. 

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