Aromatic cation activation of alcohols: conversion to alkyl chlorides using dichlorodiphenylcyclopropene.

A novel paradigm for the activation of alcohols toward nucleophilic displacement via formation of cyclopropenium ethers is described. The conversion of a range of alcohol substrates to the corresponding alkyl chlorides occurs rapidly upon treatment with 3,3-dichloro-1,2-diphenylcyclopropene. (1)H NMR data support the intermediacy of a cyclopropenium intermediate, and the reaction is demonstrated to proceed primarily via the S(N)2 mechanism for 1-phenylethanol. A total of 12 examples of substrate scope are provided.