Thermal aromatic Claisen rearrangement and Strecker reaction of alkyl(allyl)-aryl ethers under green reaction conditions: Efficient and clean preparation of ortho-allyl phenols (naphthols) and alkyl(allyl)oxyarene-based γ-amino nitriles

Chemical transformations of 13 diverse allyl(alkyl)-aryl ethers, easily prepared using Williamson reaction of different hydroxyarenes and allyl bromide and alkyl (n-butyl, n-octyl) bromides, were studied. Thermal aromatic Claisen rearrangement of allyl-aryl ethers to obtain ortho-allyl phenols (naphthols) employing propylene carbonate as a nontoxic and biodegradable solvent was described for the first time. The use of this green solvent allowed to enhance notably product yields and reduce significantly the reaction time comparing with the use of 1,2-dichlorobenzene, toxic solvent, which is traditionally employed in this type of Claisen rearrangement. Three-component Strecker reaction of selected alkyl(allyl)-aryl ethers with formyl function on aryl fragment, piperidine and potassium cyanide in the presence of sulfuric acid supported on silica gel (SSA, SiO2-O-SO3H) under mild reaction conditions was used in the preparation of new γ-amino nitriles, analogues of alkaloid girgensohnine [2-(4-hydroxyphenyl)-2-(piperidin-1-yl)acetonitrile], a perspective biological model in the search for new insecticidal agrochemicals against Aedes aegypti. The use of SSA, an inexpensive and reusable solid catalyst, allowed to obtain new series of 2-[4-alkyl(allyl)oxyphenyl]-2-(piperidin-1-yl)acetonitriles in short time at room temperature with good yields.