Department of Applied Chemistry, School of Engineering, The University of Tokyo, and CREST, Japan Science and Technology Agency (JST), 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan.
J Am Chem Soc. 2010 Mar 10;132(9):2866-7. doi: 10.1021/ja9107275.
Despite its inertness toward pericyclic reactions under common conditions, naphthalenes readily undergo Diels-Alder reactions when coencapsulated with a suitable dienophile within the cavity of a self-assembled host. Localization of the reactant pair significantly reduces the entropic cost of the reaction, and preorganization within the host cavity controls both the regio- and stereoselectivity of the reaction: electronically disfavored exo adducts were obtained, and with substituted naphthalenes, the reaction takes place on the less electron-rich, unsubstituted ring. Our findings highlight the fact that judicious tuning of substrate size and shape within molecular flasks can unveil new and unusual reactivities for otherwise unreactive molecules.
尽管在常见条件下，萘对周环反应表现出惰性，但当与合适的双烯体共包封在自组装主体的空腔内时，萘很容易发生 Diels-Alder 反应。反应物对的定位显著降低了反应的熵成本，而主体空腔内的预组织控制了反应的区域和立体选择性：获得了电子不利的外向加合物，并且对于取代的萘，反应发生在电子密度较低的未取代环上。我们的发现强调了一个事实，即在分子瓶中明智地调整底物的大小和形状，可以揭示原本无反应性的分子的新的和不寻常的反应性。
