A self-assembled cage as a non-covalent protective group: regioselectivity control in the nucleophilic substitution of aryl-substituted allylic chlorides

Abstract

Aryl-substituted allylic chlorides are accommodated by a self-assembled cage in such a restricted orientation that the internal reaction sites are shielded while the external ones are exposed. This non-covalent protection enhances terminal regioselectivity in the allylic substitution.

Self-assembled metal–organic polyhedra: An overview of various applications

“…The nucleophilic attack on allylic halides either takes place at the α-or γ-carbon to form two regio isomeric products and their ratio entirely depends on the steric, electronic, and polarity of solvents. Encapsulation of substituted allyl chloride inside cage 2 in the presence of AgNO 3 in D 2 O solution affords deuterated allyl alcohol via S N 1 mechanism [134]. The shielded internal reaction sites and enhanced terminal selectivity in the nucleophilic substitution is due to the non-covalent protection of the γ-carbon of allylic chloride.…”

“…Table 3 Terminal-selective nucleophilic substitution of allylic chloride within cage 2. Reproduced with permission from [134]. M a n u s c r i p t a Reaction conditions: allylic chloride, cage 1 (0.5 eq.…”

Clam‐like Cyclotricatechylene‐based Capsules: Identifying the Roles of Protonation State and Guests as well as the Drivers for Stability and (Anti‐)Cooperativity

“…Molecular capsules are supramolecules that are often used in host-guest chemistry for various potential applications, such as sensing of molecules and ions, [1] stabilising short-lived molecular species, [2,3] and using the capsules as nano reaction vessels. [4][5][6][7][8] The interactions between guest and host can be covalent [9] or ionic in nature, [10] explained through hydrogenbonding effects, [7,8,[11][12][13] metal-ligand coordination, [14][15][16][17][18] or hydrophobic interactions, [19] or a combination of all the aforementioned effects. [20,21] One of the many examples for a host molecule that noncovalently captures its guest is the macrocyclic compound cyclotriveratrylene (CTV), which assumes a bowl-shaped crown conformation.…”

“…In the same study, attempts to form a capsule that enclosed K + were unsuccessful. Instead, the ion associated with aromatic π surfaces of a single ctcH 5 À unit. , the clams partially open up in order to accommodate a large cation.…”

“…The aforementioned studies were limited to a few selective protonation states; i. e. [Rb(ctcH 5 )(ctcH 4 )] 2À , [Cs(ctcH 5 )(ctcH 4 )] 2À , [Rb(ctcH 5 ) 2 ] À and [Cs (ctcH 5 ) 2 ] À . These clam-like units were identified in crystal structures with different counterions, e. g. [Rb(ctcH 5 )(ctcH 4 )] 2À units were identified in [C(NH 2 ) 3 ] 2 [Rb(ctcH 5 )(ctcH 4 )] · 15H 2 O and Rb 2 [Rb(ctcH 5 )(ctcH 4 )] · 3.5H 2 O, [Cs(ctcH 5 )(ctcH 4 )] 2À in [C(NH 2 ) 3 ] 2 [Cs (ctcH 5 )(ctcH 4 )] · 2(CH 3 ) 2 CO · 5H 2 O, while a single K(ctcH 5 ) unit was identified in K(ctcH 5 ) · C 2 H 5 OH. However, to better understand the formation of such capsules, it is important to treat all systems on an equal footing.…”