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Paper | Regular issue | Vol 31, No. 3, 1990, pp.447-457
Published online, 1st January, 1970
DOI: 10.3987/COM-88-4855
Improving Regioselectivity under Phase Transfer Conditions: Effect of Chemical Parameters and Kinetic Study of Indole N-Alkylation

Mohamed Bourak and Roger Gallo*

*ESIPSOI, U.A. 126 C.N.R.S., Fac Sciences et Tech. St. Jerome, 13013 Marseille Cedex 13, France


The results obtained by changing the nature of catalyst, solvent, HaOH concentration, nature or ratio of reagents and reaction procedure are discussed for the alkylation of indole by benzyl halide under PTC conditions. Besides N-benzylindole other isomers are formed with the intermediate 3-benzylindole being detected at early reaction stage. Formation of benzyl alcohol (and ether) and of tertiary amine occurs in parallel. The relative rate constant with the leaving group chloride compared to bromide is 1/57, but the overall yield and selectivity in 1-alkylation is increased. Rate constants and activation parameters are reported. Butyl and heptyl halides show similar behavior. The results are discussed in light of the general problem of change in nucleophilic ambident reactivity of heterocycles induced under phase transfer conditions.