The Gatterman – Koch reaction is a method for the formation of arenes (including polycyclic arenas) by the action of carbon monoxide and hydrogen chloride on them in the presence of Lewis acids :
It was proposed by Ludwig Gatterman and Julius Arnold Koch in 1897 [1] .
Content
Reaction mechanism
The Gatterman-Koch reaction during catalysis with Lewis acids is a variant of Friedel-Crafts acylation , however, the initially expected formation of unstable formyl chloride from carbon monoxide and hydrogen chloride has not been confirmed. It is assumed that, as in the case of Friedel-Crafts acylation, the activation of carbon monoxide is due to the donor-acceptor binding of an electron oxygen pair to Lyuis acid, leading to the formation of a carbocation intermediate and further electrophilic substitution reaction in the aromatic core:
When carrying out the reaction in superacid conditions, i.e. when used as a catalyst, antimony pentafluoride in hydrogen fluoride as an electrophilic acylating particle is the HCO + cation formed during the protonation of carbon monoxide [2] .
Applicability and modifications
The Gatterman – Koch reaction, as well as Friedel-Crafts acylation, occurs during catalysis with Lewis acids ( aluminum chloride, zinc chloride , etc.), and aluminum chloride is most often used.
Benzene, alkyl benzenes, and also condensed aromatic compounds enter into the reaction, the formylation is in peri- position to the existing substituent, only one formyl group enters into the aromatic core.
When carrying out the reaction at atmospheric pressure, copper (I) chloride is used as a promoter [3] ; under laboratory conditions, an equimolar mixture of carbon monoxide is obtained by the action of chlorosulfonic acid on formic acid :
At a pressure of 50–200 atm, the reaction proceeds in good yields and in the absence of copper chloride, the yields thus reach 90%, however, side processes of isomerization and disproportionation of alkyl benzenes are possible.
Phenols, their esters and aromatic amines do not react.
In 1949, a modification of the method was proposed in which hydrogen fluoride was used instead of hydrogen chloride, and boron trifluoride was used as a catalyst and the reaction was carried out under high pressure [4] , but in modern laboratory practice a modification of this method is used, in which instead of a mixture of carbon monoxide and hydrogen fluoride is used relatively stable formyl fluoride at atmospheric pressure, formyl fluoride is synthesized by the interaction of formic and acetic acid mixed anhydride with anhydrous hydrogen fluoride:
Notes
- ↑ Gattermann, L .; Koch, JA Eine Synthese aromatischer Aldehyde (German) // Ber. : magazin. - 1897. - Bd. 30 - S. 1622} . - DOI : 10.1002 / cber.18970300288 .
- ↑ Tanaka, Mutsuo; Masahiro Fujiwara, Qiang Xu, Yoshie Souma, Hisanori Ando, Kenneth K. Laali. Evidence for the Intracomplex Reaction in Gattermann-Koch Formylation in Superacids: Kinetic and Regioselectivity Studies (Eng.) // Journal of the American Chemical Society : journal. - 1997. - Vol. 119 , no. 22 - P. 5100-5105 . - ISSN 0002-7863 . - DOI : 10.1021 / ja9641012 .
- ↑ LI Jie Jack. Name Reactions: A Collection of Detailed Reaction Mechanisms . - 2nd. - Springer , 2003. - P. 157. - ISBN 3540402039 .
- ↑ US Patent 2,485,237 to EI du Pont de Nemours,
See also
- Gutterman reaction
- Friedel-Crafts Reaction