Binding orientation and reactivity of alkyl α,ω-dibromides in water-soluble cavitands

Abstract

Host–guest complexation of α,ω-dibromides showed rabid tumbling conformation on NMR timescales and afforded mono hydroxyl bromides after hydrolysis in D2O.

Molecules in Confined Spaces: Reactivities and Possibilities in Cavitands

“…Further examples include hydrolysis of dihalides. 44 What Might Be Done Cavitand Applications in C-H Activation Truly remote C-H activation is an unmet need. More than 40 years ago, Breslow 45 recognized the limitations of the conventional, nearby functionalization offered by Hofmann-Loeffler-Freitag (HLF) reactions, Barton oxidation, or related reactions.…”

Highly Selective Radical Monoreduction of Dihalides Confined to a Dynamic Supramolecular Host

“…The vase is stabilized by guests that fill the inner space, and the guests’ nuclei experience upfield shifts in their NMR spectra, due to the anisotropic effect of the many aromatic panels of the host. Recently, we successfully reported these cavitands as reaction vessels in non‐radical processes involving cyclizations [18–20] and mono‐functionalizations [21–23] . Free radicals are highly reactive species with fast kinetics (often k >10 3 m −1 s −1 ) and low discrimination.…”

“…Recently,w es uccessfully reported these cavitands as reactionv essels in non-radical processes involving cyclizations [18][19][20] and mono-functionalizations. [21][22][23] Free radicals are highly reactive species with fast kinetics (often k > 10 3 m À1 s À1 ) and low discrimination.S electivity in product distribution is often achallenge for such species and only afew selectiverad-ical processes have been reported in supramolecular hosts. Ramamurthya nd co-workers [24,25] have investigated radicals generated in capsular hosts, where they determined the effects of confinement on product selectivity.…”

“…Solvolysis is ap ossible side reactionw hen alkyl halidesa re involved in aqueous medium, due to their relativelyh igh reactivity towards nucleophiles (i.e.,w ater). However,a ctivators such as DMSO are required to promote this reaction, [21,29] so use of this co-solvent was avoided in these studies.…”

Rigid, biconical hydrogen-bonded dimers that strongly encapsulate cationic guests in solution and the solid state

“…Conned spaces within self-assembled capsules are distinct from the bulk solvent, sequestering complementary guests 1 or catalysing chemical reactions. [2][3][4] The volume and morphology of the cavity depends upon the size and shape of the monomers: Rebek's highlycurved arcs homo-dimerize into the spherical tennis balls 5 and soballs 6 (Fig. 1a), whereas the shallow and exible bowls resorcin [4]arenes and pyrogallol [4]arenes form hexamers [7][8][9][10][11][12][13][14] or dimers [15][16][17][18][19][20][21][22] (Fig.…”