Phenonium ions from the addition of phenyl cations to alkenes. Photochemical synthesis of (rearranged) aminoalkylanilines from haloanilines in the presence of alkenes and amines.
beta-Aminoalkylanilines are smoothly obtained by irradiation of 4-chloro- and 4-fluoroanilines (as well as the N,N-dimethyl derivatives) in the presence of alkenes (1-hexene, cyclohexene) and amines (butylamine, piperidine) in polar, protic solvents such as trifluoroethanol (yield 40-75%). The reaction involves photoheterolysis of the haloaniline, addition of the resulting phenyl cation to the alkene and trapping of the phenonium cation by amine. A fraction (up to ca. 20%) of aminoalkylanilines resulting from Wagner-Meerwein rearrangement of the phenonium cation is obtained in some cases. Reduction and direct trapping of the phenyl cation by the amine compete with the above three-component synthesis in a less stabilizing solvent such as acetonitrile, but not in CF(3)CH(2)OH.
Guizzardi
Benedetta
B
Department Organic Chemistry, University of Pavia, Via Taramelli 10, 27100 Pavia, Italy.
Mella
Mariella
M
Fagnoni
Maurizio
M
Albini
Angelo
A