Taming of the DIBAL Promoted Debenzylation of α-Cyclodextrin. Kinetics, Substituent Effects and Efficient Synthesis of Lings Tetrol**

Publikation: Bidrag til tidsskriftTidsskriftartikelForskningfagfællebedømt

Dokumenter

  • Fulltext

    Forlagets udgivne version, 2,42 MB, PDF-dokument

The kinetics of the reaction of perbenzyl α-cyclodextrin was studied varying the concentration of DIBAL and substrate, and the temperature. The initial debenzylation was found to be 1st order in substrate and follow the relationship 0.0675+0.179[DIBAL]2 with respect to the concentration of DIBAL. The second and the third debenzylation which led to the 3A,6A,6D-triol (Lings triol) were both found to be 1st order in substrate concentration and zero order in DIBAL concentration. Longer reaction times with DIBAL in high concentration gave further debenzylation to comparatively complex mixtures containing the 2B,3A,6A,6D-tetrol and the 3A,6A,6C,6D-tetrol. In contrast reaction at 0.1 M DIBAL gave the symmetrical 3A,6A,3D,6D-tetrol (Lings tetrol) in 60 % yield. The effect of chlorine or methyl substitution of the phenyl groups of perbenzyl α-cyclodextrin was also investigated. Per 4-chlorobenzyl slowed down the reaction with DIBAL, while 4-methylbenzyl increased the reaction rate, but still gave the corresponding 6 A-monool or 6A,6D-diol products. A Hammett reaction constant of −4.9 was found for the first debenzylation showing a high degree of positive charge in the transition state. The per(2,4-dichlorobenzyl)-α-cyclodextrin-derivative was completely resistant to DIBAL, however upon addition of trimethyl aluminium this derivative also reacted to give the 6A,6D-diol product.

OriginalsprogEngelsk
Artikelnummere202200564
TidsskriftChemistry - A European Journal
Vol/bind28
Udgave nummer29
Antal sider13
ISSN0947-6539
DOI
StatusUdgivet - 2022

Bibliografisk note

Publisher Copyright:
© 2022 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.

Antal downloads er baseret på statistik fra Google Scholar og www.ku.dk


Ingen data tilgængelig

ID: 303457103