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Solvent and Base in One: Tetra‐ n ‐butylammonium Acetate as a Multi‐Purpose Ionic Liquid Medium for Ru‐Catalyzed Directed Mono‐ and Di‐ o ‐C–H Arylation Reactions
Author(s) -
Zou YaLing,
Wang ZhenYu,
Feng YinMao,
Li YouGui,
Kantchev Eric Assen B.
Publication year - 2017
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.201701022
Subject(s) - chemistry , ionic liquid , catalysis , acetophenone , bromide , medicinal chemistry , aryl , organic chemistry , base (topology) , solvent , imine , alkyl , mathematical analysis , mathematics
Ru‐catalyzed directed o ‐C–H arylation reactions of 2‐phenylpyridine, N ‐phenylpyrazole, acetophenone N ‐( p ‐methoxyphenyl)imine, and 2‐phenyloxazoline proceed in good to excellent yields with a number of functionalized aryl and heteroaryl bromides in neat Bu 4 NOAc at 120 °C. The acetate ion acts as the base and the relatively low melting point Bu 4 N salts (a mixture of acetate and bromide) behave as an ionic liquid. Arylation reactions of 2‐phenyloxazoline proceed with concomitant oxazolidine cleavage to give 2‐( N ‐acetylamino)ethyl benzoates promoted by side product CH 3 COOH. The dual‐purpose ionic liquid medium is compatible with both ligandless Ru for di‐arylation (optimal pre‐catalyst: RuCl 3 · x H 2 O) and Ru‐phosphane (optimal pre‐catalyst: [RuCl 2 ( p ‐cymene)] 2 /P( p ‐Tol) 3 1:4) catalysts (1–5 mol‐%) for selective mono‐arylation.