AbstractAllyl aryl ethers which have no strongly electron attracting substituents undergo a charge‐induced [3 s, 3 s] sigmatropic rearrangement in the prescence of 0.7 mole boron trichloride in chlorobenzene at low temperature, to give after hydrolysis the correspondingo‐allyl phenols (Tables 1 and 2). The charge induction causes an increase in the reaction rate relative to the thermalClaisenrearrangement of ∼1010. With the exception of allyl 3‐methoxyphenyl ether(5),m‐substituted allyl aryl ethers show similar behaviour (with respect to the composition of the product mixture) to that observed in the thermal rearrangement (Table 3). The rearrangement of allyl aryl ethers with an alkyl group in theo‐position, in the prescence of boron trichloride, yields a mixture ofo‐ andp‐allyl phenols, where morep‐product is present than in the corresponding product mixture from the thermal rearrangement (Table 4). This ‘para‐effect’ is especially noticeable foro‐alkylated α‐methylallyl aryl ethers (Table 5 ).With boron trichloride, 2,6‐dialkylated allyl aryl ethers give reaction products which arise, in each case, from a sequence of anortho‐Claisenrearrangement followed by a [1,2]‐, [3,3]‐ or [3,4]‐shift of the allyl moiety (Tables 6 and 7). Ally1 mesityl ether (80), with boron trichloride, gives pure 3‐ally1 mesitol (95). From phenol, penta‐ally1 phenol (101) can be obtained by a total of five O‐allylations followed by three thermal and two boron trichloride‐induced rearrangements.The sigmatropic rearrangements of the ethers studied, using D‐ and14C‐labelled compounds, are collected in scheme 2; only the reaction steps indicated by heavy arrows are of importance.With protic acids, there is a [3,3]‐shift of the allyl group in 6‐allyl‐2,6‐disubstituted cyclohexa‐2,4‐dien‐l‐ones, while with boron trichloride the [3,3]‐reaction is also observed along with the much less important [1,2]‐ and [3,4]‐transformations (Table 8). 4‐Allyl‐4‐alkyl‐cyclohexa‐2,5‐dien‐1‐ones give only [3,3]‐rearrangements with boron trichloride (Table 9). As expected, the naphthalenone112, which is formed by allowing boron trichloridc to react for a short time with allyl (1‐methyl‐2‐naphthyl) ether (111), undergoes only a [3,4] rearrangement (Scheme 3).Representations of how, in our opinion, the complex behaviour of allyl aryl ethers and allyl cyclohexadienones under the influence of boron trichloride, can be rationalized are collected together in Schemes 4 and 5.In the last part of the discussion secti