Abstract:Simple Brønsted acids such as p-toluenesulfonic acid monohydrate (PTS) or polymer-bound p-toluenesulfonic acid efficiently catalyze the direct nucleophilic substitution of the hydroxy group of allylic and benzylic alcohols with a large variety of carbon-and heteroatom-centered nucleophiles. Reaction conditions are mild, the process is conducted under an atmosphere of air without the need for dried solvents, and water is the only side product of the reaction.Keywords: alcohols; C À C coupling; nucleophilic substitution; supported catalysts; synthetic methodsThe construction of C À C bonds is a fundamental reaction in organic synthesis and coupling reactions between reactive nucleophiles (NuH) and halides (RX) or related species are one of the most used strategies. In this context, direct substitution of the hydroxy group in alcohols by nucleophiles could be considered as an ideal process because of the wide availability of the starting materials and the generation of H 2 O as the only side product. However, the main limitation of this strategy is that an excess of sulfuric acid, polyphosphoric acid, [1] or a stoichiometric amount of a Lewis acid [2] is required, and so the range of possible nucleophiles is limited. Therefore, the development of catalytic versions of this reaction remains as a major objective of the modern organic chemistry (Scheme 1). Recent advances in this field are based on the use of transition metal complexes as catalysts. Remarkable are the Ru-, [3] Re-, [4] and Au-catalyzed [5] propargylation of nucleophiles with propargylic alcohols, the Tsuji-Trost reaction of allylic alcohols with active methylene compounds, [6] the reaction of secondary benzylic alcohols with different nucleophiles catalyzed by La, Sc, or Hf salts, [7] and the Fe-, or Au-catalyzed arylation of benzylic alcohols.[8] In addition, InCl 3 has emerged as a powerful catalyst to perform direct nucleophilic substitution of allylic and benzylic alcohols. [9] Although the catalytic activation of alcohols is thought to be difficult due to the poor leaving ability of the OH group, we have recently found that simple Brønsted acids like p-toluenesulfonic acid monohydrate (PTS) catalyze the direct nucleophilic substitution of propargylic alcohols.[10] Herein we report a strategy involving simple Brønsted acid-catalyzed activation of allylic and benzylic alcohols as a method for the direct formation of new C À C and C À heteroatom bonds from carbon (active methylene compounds, aromatic and heteroaromatic compounds), nitrogen, sulfur, and oxygen nucleophiles and alcohols. Surprisingly, the Brønsted acid-catalyzed direct substitution of allylic alcohols has not been reported in the literature and so no systematic study has so far been performed. Moreover, in some recent papers this reaction has been reported not to proceed at all. [9b] Despite all these negative forewarnings, we decided to investigate the reaction of allylic alcohol 1a as a model substrate with selected nucleophiles 2-8 under PTS-catalyzed conditions (Sche...

Two protein bands with laccase activity were found after PAGE of culture liquid or mycelium extract of Pleurotus eryngii, grown on glucose-ammonium tartrate-yeast extract medium with and without inducers. A major and a minor laccase band were observed in the basal medium. The intensity of the major band (laccase I) did not change after the addition of inducers. However, the minor band (laccase II), characterized by higher electrophoretic mobility, was strongly induced by wheat-straw alkalilignin and vanillic and veratric acids. Laccase activity in the basal medium had an optimum pH of 4.5 and was stable from pH 3 to 10 during 24 h at room temperature. This enzyme had wide substrate specificity on hydroquinones, methoxy-substituted monophenols, and aromatic amines. In general, laccase activity was found only with compounds having a redox potential lower than 0.5 mV. The highest activity was obtained with methoxy- and methyl-substituted p-hydroquinones and aromatic diamines. Some activity also occurred with the aliphatic compound 3,5-cyclohexadiene-1,2-diol.

Simple Brønsted acids such as p-toluenesulfonic acid monohydrate (PTS) efficiently catalyze a direct substitution of the hydroxyl group in propargylic alcohols with 1,3-dicarbonyl compounds. Selective propargylation or allenylation is obtained depending on the nature of the alkynol. Reactions can be performed in air in undried solvents with water being the only side product of the process. By applying this reaction as the key step, a range of interesting polysubstituted furans can easily be synthesized in a one-pot procedure. [reaction: see text].