Dual Lewis Acid/Lewis Base Catalyzed Acylcyanation of Aldehydes: A Mechanistic Study
2016 (English)In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 22, no 11, 3821-3829 p.Article in journal (Refereed) PublishedText
A mechanistic investigation, which included a Hammett correlation analysis, evaluation of the effect of variation of catalyst composition, and low-temperature NMR spectroscopy studies, of the Lewis acid-Lewis base catalyzed addition of acetyl cyanide to prochiral aldehydes provides support for a reaction route that involves Lewis base activation of the acyl cyanide with formation of a potent acylating agent and cyanide ion. The cyanide ion adds to the carbonyl group of the Lewis acid activated aldehyde. O-Acylation by the acylated Lewis base to form the final cyanohydrin ester occurs prior to decomplexation from titanium. For less reactive aldehydes, the addition of cyanide is the rate-determining step, whereas, for more reactive, electron-deficient aldehydes, cyanide addition is rapid and reversible and is followed by rate-limiting acylation. The resting state of the catalyst lies outside the catalytic cycle and is believed to be a monomeric titanium complex with two alcoholate ligands, which only slowly converts into the product.
Place, publisher, year, edition, pages
Wiley-VCH Verlagsgesellschaft, 2016. Vol. 22, no 11, 3821-3829 p.
asymmetric catalysis, Lewis acids, Lewis bases, reaction mechanisms, titanium
IdentifiersURN: urn:nbn:se:kth:diva-184528DOI: 10.1002/chem.201503782ISI: 000371741400037ScopusID: 2-s2.0-84959536218OAI: oai:DiVA.org:kth-184528DiVA: diva2:917432
QC 201604062016-04-062016-04-012016-04-06Bibliographically approved