Phenols are not acetylated by acetic anhydride alone in carbon tetrachloride, but addition of pyridine leads to acetylation. Alcohols, in contrast, are acetylated in the absence of pyridine, but the extent of catalysis by pyridine is less than for phenols. The fact that a maximum rate of acetylation of p-chlorophenol is reached as the pyridine concentration is increased is most readily interpreted in terms of a reaction proceeding only through a hydrogenbonded form of the phenol.p-Chloro[hydroxy-2H]phenol (4 g.) was prepared by dissolving p-chlorophenol in deuterium oxide (0-5 g. ; 99.95

borane, crystallized from water, and dehydrated a t 110 "C to give the anhydride, (PhBO),,l2 Dihydroxy-(n-butyZ)bora.lze. This was prepared according to the method of Snyder et aE.13Boronates. The cyclic derivatives were prepared by the azeotropic removal of water and toluene from a 3 : 1 molar mixture of the appropriate diol to anhydride. When the theoretical quantity of water was removed, the excess of toluene was removed under reduced pressure and the boronate was purified by vacuum distillation. The acyclic boronates, (EtO),BR (R = Ph and Bun) were prepared from the dihydroxyborane and alcohol according to Gerrard's procedure.14 3-Phenyl-2,4-dioxa-3-borabicyclo[3,2, 21nonane was purified by vacuum sublimation a t 70 "C and 0-05 mm. Hg. The yield of this last compound was only ca. 40% as commercial samples of cyclohexane-l,4-diol (quinitol) are an approximately equimolar mixture of the cis-and transforms. cis-Quinitol yields a cyclic product [equation (l)]

Acyl Trifluoroacetates. Part 1V.l Trifluoroacetylation of Hydroxycompounds w i t h Trifluoroacetic Anhydride By T. G. Bonner," P. M. McNamara, and (in part) B. Smethurst, Royal Holloway College, University of Alcohols and phenols are trifluoroacetylated in carbon tetrachloride much more rapidly by trifluoroacetic anhydride than by acetyl trifluoroacetate. Pyridine bases are effective catalysts for the trifluoroacetylation of phenols but not of alcohols or thiophenoi, and this effect is attributed to phenolic compounds showing greater nucleophilicity through hydrogen-bonding with the base.London, Englefield Green, Egham, Surrey THE fact that hydroxy-compounds are more rapidly trifluoroacetylated by trifluoroacetic anhydride than by acetyl trifluoroacetate in carbon tetrachloride must arise, at least partly, because the trifluoroacetate anion is a better leaving-group 2*3 than the acetate ion. The importance of this effect is evident from the very similar rates in carbon tetrachloride at 0" of acetylation of 9-chlorophenol by acetyl trifluoroacetate (1.1 x 10-4 sec.-l) and of trifluoroacetylation of the same substrate by trifluoroacetic anhydride (0.9-1*0 x sec.-l). The rate in both cases appears to depend markedly on the bond-breaking step in the anhydride.The change from predominant acetylation of phenols by acetyl trifluoroacetate to a faster trifluoroacetylation reaction on addition of pyridine bases has been attributed t o an increase in the nucleophilicity of the hydroxy-Part 111, T.

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