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Copper(II) Triflate as a Source of Triflic Acid: Effective, Green Catalysis of Hydroalkoxylation Reactions
Author(s) -
Tschan Mathieu J.L.,
Thomas Christophe M.,
Strub Henri,
Carpentier JeanFrançois
Publication year - 2009
Publication title -
advanced synthesis and catalysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.541
H-Index - 155
eISSN - 1615-4169
pISSN - 1615-4150
DOI - 10.1002/adsc.200800750
Subject(s) - chemistry , trifluoromethanesulfonate , catalysis , triflic acid , lewis acids and bases , polymerization , reagent , organic chemistry , brønsted–lowry acid–base theory , norbornene , polymer chemistry , polymer
The hydroalkoxylation of dicyclopentadiene (DCPD) and norbornene (NB) with 2‐hydroxyethyl methacrylate (HEMA) for the synthesis of industrially relevant monomers has been investigated with various metal‐based Lewis acids and strong Brønsted acids. In the absence of other additives, copper(II) triflate is the most efficient catalyst system. Kinetics, electron spin resonance (ESR), catalyst poisoning and cross experiments indicate that triflic acid (TfOH) is the true active catalyst in these reactions. This in situ generation of TfOH occurs via reduction of Cu(OTf) 2 by the olefin reagent (DCPD, NB). The copper ions present in the reaction mixture act as radical polymerization retardants, preventing polymerization of HEMA (which is observed with most other metal salts and strong Brønsted acids investigated), thus improving the selectivity and yield (up to 95%) for the desired products. These observations have led to the development of a highly effective green process, using bulk reagents (no solvent) and a cheap, metal‐free catalyst system, based on TfOH and a phenolic radical inhibitor (2,5‐di‐ tert ‐butylhydroxytoluene, BHT).