[4+2] and [2+2] Cycloadditions in Confined Cavity

Significance

The authors report thermal [4+2] and photochemical [2+2] cycloadditions of unactivated aromatic molecules inside the cavity of a self-assembled tetramer (1a-c), a complex which has been previously reported (J. Am. Chem. Soc. 2004, 126, 6846). It is notable that relatively unreactive arenes such as 2 and 4 undergo efficient cycloadditions with dienophile 3. Furthermore, the reaction products are exclusively endo and syn for [4+2] and [2+2] cycloadditions, respectively. The presence of hydrophobic reaction sites in water is the key to the observed reactivity.