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Efficient Solvent‐Free Friedel‐Crafts Benzoylation and Acylation of m ‐Xylene Catalyzed by N ‐Acetylpyrazine‐2‐carbohydrazide‐Fe(III)‐chloro Complexes
Author(s) -
Barman Tannistha Roy,
Sutradhar Manas,
Alegria Elisabete C. B. A.,
Guedes da Silva M. Fátima C.,
Kuznetsov Maxim L.,
Pombeiro Armando J. L.
Publication year - 2018
Publication title -
chemistryselect
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.437
H-Index - 34
ISSN - 2365-6549
DOI - 10.1002/slct.201801656
Subject(s) - chemistry , catalysis , yield (engineering) , friedel–crafts reaction , medicinal chemistry , acylation , lewis acids and bases , anhydrous , toluene , electrochemistry , inorganic chemistry , organic chemistry , materials science , metallurgy , electrode
Reaction of N ‐acetylpyrazine‐2‐carbohydrazide (H 2 L) with anhydrous Fe(II) or Fe(III) chloride in CH 3 CN or in MeOH leads to the mononuclear [Fe( κ NN'O‐HL)Cl 2 ] ( 1 ) or binuclear [Fe( κ NN'O‐HL)Cl( μ ‐OMe)] 2 ( 2 ) Fe(III) complex, respectively. These complexes are characterized by elemental analysis, ESI‐MS, IR spectroscopy, single‐crystal X‐ray crystallography, electrochemical techniques and DFT calculations. The theoretical calculations indicate that the three single‐electron sequential reductions of 1 are centred at the metal, at the pyrazine group and at both, respectively. The catalytic activity of 1 and 2 was screened towards Friedel‐Crafts benzoylation and acylation of m ‐xylene. The effects of reaction parameters, such as catalyst amount, reaction time and temperature, were studied and, under optimal conditions, 96% yield of 2,4‐dimethylbenzophenone and 20% yield of 2,4‐dimethylacetophenone were obtained, respectively. Complex 1 exhibited the highest activity in both reactions. The structural and electrochemical properties were supported by theoretical calculations and the importance of the Lewis acid character of the catalyst in the promotion of this catalytic reaction is discussed.