Catalysis of the bromination of phenols and phenoxide ions in aqueous solution by .alpha.-cyclodextrin

Biomimetic Reactions Catalyzed by Cyclodextrins and Their Derivatives

“…The bromination of anisole and some phenols shows at most a slight acceleration by R-CD and is often retarded because tribromide ion binds into the cyclodextrin cavity. 145,146 However, R-CD catalyzes the debromi- 6) 112 or as a dimer (7). 113 Figure 5.…”

“…Also, there are many examples in which the point of reaction of an external reagent is influenced when a substrate binds into a cyclodextrin cavity − ,− but so far with no evidence that the cyclodextrin catalyzes the process as it does in the HOCl chlorinations. The bromination of anisole and some phenols shows at most a slight acceleration by α-CD and is often retarded because tribromide ion binds into the cyclodextrin cavity. , However, α-CD catalyzes the debromination of some bromocyclohexadienones (the proposed mechanism is shown in Figure ), the reverse of one of the steps in the bromination of aromatic rings. , α-CD also modestly catalyzes the reaction of formic acid with bromine 7 Cyclodextrin binding promotes the alkylation of substrate 8 140 and the debromination of a bromocyclohexadienone …”

Selectivity enhancement of aromatic halogenation reactions at the micellar interface: effect of highly ionic media

“…However, most of these methods have some limitations such as the use of strong and/or specialized halogenating agents, toxic and expensive reagents, low yields, and long reaction times. The pioneering kinetic studies were done on chlorination and bromination reactions [26,27].…”

Proteïnes com a microreactors en fotoquímica supramolecular

“…Les ciclodextrines són oligosacàrids cíclics formats usualment per 6, 7 o 8 unitats de D-(+)-glucopiranosa i en general es produeixen per hidròlisi enzimàtica [30] . Són unes macromolècules molt atractives ja que, d"una banda, tenen una cavitat hidrofòbica on poden unir-se certs hostes i, de l"altra, posseeixen grups hidroxil que poden bé permetre A la bibliografia es troben nombrosos exemples de com diverses ciclodextrines i ciclodextrines modificades són capaces de catalitzar reaccions simples del tipus DielsAlder [31,32] , alquilacions [33] , halogenacions [34] , deshalogenacions [35] , fosforilacions [36] , etc. I també reaccions més complexes mimetitzant enzims tals com estearases [37] , glioxalases [38] , transaminases [39] o epoxidases [40] .…”

“…A banda d"això, també s"han trobat força patents referents a l"encapsulació de l"avobenzona en aquestes ciclodextrines [24][25][26][27] però també en liposomes [28,29] , microcàpsules de sol-gel [30,31] , resines [32][33][34] , etc. Això mostra que l"encapsulació de l"avobenzona a l"interior de diversos tipus d"estructures supramoleculars és factible d"utilitzar-se en la formulació real de filtres solars ja que, en general, milloren l"estabilitat i les propietats dels filtres.…”