Gassman reaction
The Gassman reaction is a name reaction in organic chemistry . It was first published in 1972 by Paul G. Gassman (1935–1993). This reaction can be used to prepare ortho- alkylated anilines :
With a slight modification, it is also possible to synthesize anilines with a vinyl , alkyl or benzaldehyde group in the ortho position. The Gassman reaction is related to the Gassman indole synthesis and to the Gassman oxindole synthesis .
mechanism
The mechanism described here was proposed by Zerong Wang:
Tert-butyl hypochlorite ( 1 ) is split homolytically into a chlorine radical and a tert- butyloxy radical. The latter reacts with aniline to form tert- butanol and forms a radical aniline intermediate 2 . This recombines with the previously created chlorine radical to form N -chloroaniline ( 3 ). If this is mixed with an organic sulfide , the sulfonium cation 4 is obtained . This is worked up with triethylamine , whereby the zwitterion 5 is formed with elimination of triethylamine hydrochloride . An intramolecular nucleophilic attack now takes place, producing the imine 6 . Then an elimination reaction takes place, which leads to the rearomatization of the ring and the formation of the aniline 7 . The ortho- substituted aniline 8 is obtained by adding Raney nickel with desulphurization .
There is a modification in which, instead of tert-butyl hypochlorite, sulfuryl chloride is used to carry out the necessary N -chlorination of aniline. Other variants make it possible to produce para- substituted anilines with the help of the Gassman reaction .
Examples
The following example is intended to illustrate the possible applications and practical benefits of the Gassman reaction .
The reaction of p -toluidine 9 to form 2-benzyl-4-methylaniline 11 is shown here as an example, the aniline derivative 10 being formed as an intermediate stage ; Ar denotes a phenyl radical . The methyl radical used here as an example can also be replaced by hydrogen, chlorine, a nitro group or an acetate radical.
Individual evidence
- ↑ a b c d e after: Z. Wang (Ed.): Comprehensive Organic Name Reactions and Reagents, 1 Volume Set , John Wiley & Sons, Hoboken, New Jersey 2009, pp. 1198-1201, ISBN 978-0-471 -70450-8 .
- ^ Paul G. Gassman. Retrieved June 18, 2013 .
- ^ A b c Paul G. Gassman, H. Roger Drewes: The ortho functionalization of aromatic amines. Benzylation, formylation, and vinylation of anilines . In: Journal of the American Chemical Society . tape 100 , no. 24 , 1978, p. 7600–7610 , doi : 10.1021 / ja00492a028 .