ACIDITY EFFECT IN THE REGIOCHEMICAL CONTROL OF THE ALKYLATION OF PHENOL WITH ALKENES

Treatment of 1:1 mixtures of phenol and linear alkenes in the presence of an acidic promoter in CHCl3 at room temperature results in ortho-r egioselective monoalkylation producing sec-alkylphenols in 48-60% yiel d. In similar reactions, branched alkenes lead exclusively to the corr esp ending para-tert-alkylhenols in 80-85% yield. Addition of increasi ng amounts of potassium phenolate to the reacting system reduces the p rotic acidity and promotes ortho-regioselective tert-alkylation. These results are tentatively explained in terms of competition of 'H-bond- template' and 'charge-controlled' mechanisms.