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[bmim][Br] as an Inexpensive and Efficient Medium for the Barbier‐Type Allylation Reaction Using a Catalytic Amount of Indium: Mechanistic Studies
Author(s) -
Dey Papiya,
Koli Mrunesh,
Goswami Dibakar,
Sharma Anubha,
Chattopadhyay Subrata
Publication year - 2018
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/ejoc.201800043
Subject(s) - chemistry , catalysis , ionic liquid , bromide , metal , allyl bromide , carbene , medicinal chemistry , indium , solvent , organic chemistry
Barbier‐type allylation reactions of aldehydes and ketones have been carried out with both unsubstituted and γ‐substituted allyl bromides using only a catalytic amount (0.1 equiv.) of In metal in [bmim][Br], but not in H 2 O, organic solvents, or other room‐temperature ionic liquids. The reactions did not require any metal activator and proceeded chemo‐ and regioselectively. The results of time‐dependent 1 H NMR studies suggested that besides acting as a solvent, [bmim][Br] also activates the In metal surface by electron polarization to generate both CH 2 =CHCH 2 –In ( I ) and CH 2 =CHCH 2 –InBr 2 ( II ) from allyl bromide and In. Of the active allylating intermediates, species II was regenerated by the in situ reduction of InBr 3 with an imidazolium‐based N‐heterocyclic carbene, both produced during the process, accounting for the catalytic action of the In metal.