Aryl carbonyls and carbinols as proelectrophiles for Friedel–Crafts benzylation and alkylation

Abstract

Friedel–Crafts benzylation/alkylation using benzylic alcohols and aryl carbonyls as proelectrophiles is achieved using borane-ammonia and TiCl4.

Titanium tetrafluoride catalysis for the dehydrative conversion of diphenylmethanols to symmetric and unsymmetric ethers

“…We had earlier established that the chlorination and bromination occurs via a carbocation, 25 which was confirmed by carrying out a Friedel–Crafts reaction with pro-electrophiles, such as alcohols in the presence of the latter reagents. 27 It is known that alcohols and amines form a complex with titanium tetrafluoride. 29 Once this occurs, an S N 1 pathway can be envisaged for the formation of the ether involving an intermediate carbocation ( Scheme 2 ).…”

“… 25 We had postulated that the halogenation of DPM and alcohols proceeds via a carbocation intermediate and, indeed, recently reported on the use of benzyl alcohols as pre-electrophiles for Friedel–Crafts reactions in the presence of TiCl 4 . 27 Based on a reported titanium tetrafluoride-mediated fluorination during Prins cyclization, 28 we were interested in examining the potential for a dehydroxyfluorination of alcohols using TiF 4 . Unexpectedly, the reaction of DPM with a molar equiv.…”