The ambiphilic phosphino-borane i-Pr2P(o-C6H4)BMes2 affords stable versions of key zwitterionic intermediates by reactions with diethyl azodicarboxylate or PhNCO.
The Piancatelli reaction, also called the Piancatelli rearrangement, consists in the direct conversion of furfuryl alcohols to cyclopentenone derivatives through a furan ring opening-electrocyclization process. Discovered in the late 70's, this reaction has been scarcely used for more than 40 years but recently has been the focus of particular interest from the scientific community and an increasing number of publications on the topic have emerged in the last few years. The first part of this review provides an overview of the recent achievements in classical Piancatelli reactions, discussing reaction conditions and catalytic systems, whereas the second part focuses on the variants recently developed, including the use of new nucleophiles in the process. Finally, the third part of this review deals with the recent application of this transformation to the production of commodity chemicals from renewable carbon feedstocks based on sugar-derived furanic platforms.
ISSN: 1759-9954International audienceTwo novel sugar-based fatty ester polyols were synthesized by selective transesterification of epoxidized methyl or ethyl oleate with unprotected methyl alpha-D-glucopyranoside and sucrose respectively, followed by hydrolysis of the epoxide moiety. The so-formed polyols were then used as polyurethane (PU) precursors in the polyaddition with isophorone diisocyanate (IPDI) in the presence of dibutyl tin dilaurate (DBTDL) as a catalyst. Interestingly, the reactivity of the hydroxyl functions attached to the sugar and to the fatty ester chain moieties respectively could be discriminated with respect to the solvent used, enabling the synthesis of either linear or cross-linked PUs. The linear PUs were studied by means of FTIR, H-1 NMR spectroscopy and size exclusion chromatography, SEC. The thermo-mechanical properties of these original PUs bearing pendant or intramolecular sugar units were also analyzed by differential scanning calorimetry, DSC
A novel
direct and diastereoselective amination of biosourced monobenzylated
isohexides has been developed through borrowing hydrogen methodology
using a cooperative catalysis between an iridium complex and a phosphoric
acid. We also report herein the first regio- and diastereoselective
direct amination of isosorbide.
The HF adduct of the ambiphilic phosphine-borane [o-iPr(2)P(C(6)H(4))BMes(2)] has been spectroscopically characterized and the nature of the interaction between the ensuing hydrogenophosphonium and fluoroborate moieties has been analyzed computationally.
The regio and diastereoselective direct mono or diamination of bio-based isohexides (isosorbide and isomannide) has been developed through borrowing hydrogen (BH) methodology using a cooperative catalysis between an iridium com-[a] Univ Lyon,
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