Site-selective reactions mediated by molecular containers

Abstract

In this review, we summarize various site-selective reactions mediated by molecular containers. The emphasis is on those reactions that give different product distributions on the potential reactive sites inside the containers than they do outside, free in solution. Specific cases include site-selective cycloaddition and addition of arenes, reduction of epoxides, α,β-unsaturated aldehydes, azides, halides and alkenes, oxidation of remote C–H bonds and alkenes, and substitution reactions involving ring-opening cyclization of epoxides, nucleophilic substitution of allylic chlorides, and hydrolysis reactions. The product selectivity is interpreted as the consequence of the space shape and environment inside the container. The containers include supramolecular structures self-assembled through metal/ligand interactions or hydrogen bonding and open-ended covalent structures such as cyclodextrins and cavitands. Challenges and prospects for the future are also provided.

Substrate Selectivity Imparted by Self‐Assembled Molecular Containers and Catalysts

“…This class of site-specific reactions driven by binding within unimolecular open ended molecular containers or self-assembled capsules has been recently clearly reviewed. [10] An important achievement in the field is for instance the site-selective reduction of a polyenol by a Rh(I) catalyst when operating within the metalligand tetrahedral coordination capsule developed by Bergman, Raymond and Toste, while in the absence of the host the fully hydrogenated product was observed. [11] Another outstanding example disclosed by Fujita is the functionalization of linear diterpenoids through U-shaped folding in a confined metalligand octahedral coordination cage.…”

“…Examples of specific site selectivity are interpreted as the consequence of the space and the environment inside the nanometric container. This class of site‐specific reactions driven by binding within unimolecular open ended molecular containers or self‐assembled capsules has been recently clearly reviewed [10] . An important achievement in the field is for instance the site‐selective reduction of a polyenol by a Rh(I) catalyst when operating within the metal‐ligand tetrahedral coordination capsule developed by Bergman, Raymond and Toste, while in the absence of the host the fully hydrogenated product was observed [11] .…”

Supramolecular protection with a recyclable molecular container: an efficient strategy for the one-pot selective functionalization of polyfunctional substrates

“…9 In this context, the use of macrocyclic molecular containers as supramolecular protecting units emerges as a promising strategy. 10 The general concept relies on the protection of a functional group of a polyfunctional substrate through its binding in the cavity of a molecular receptor and the subsequent selective transformation of an accessible functional group (Fig. 1b).…”

The Road Less Traveled: Unconventional Site Selectivity in Palladium-Catalyzed Cross-Couplings of Dihalogenated N-Heteroarenes

“…Alternatively, unconventional site selectivity can be achieved through the use of catalyst-controlled approaches. Although the topic of catalyst-controlled site selectivity is at the forefront of other research areas, such as C–H functionalization, relatively little is known about the relationship between catalyst structure and cross-coupling site selectivity . This Perspective surveys the handful of known examples in which unconventional or divergent site selectivity is achieved by changing the catalyst structure (e.g., through changing the ligand).…”