10.1039/c4ra04689g
The research explores a novel method for synthesizing dihydrobenzofurans, which are key structural components in many biologically active compounds. The study investigates the tandem Claisen rearrangement and intramolecular hydroaryloxylation of allyl phenyl ethers in subcritical water (SBW) using various zeolite catalysts (SBA-15, TS-1, and HZSM-5). The experiments were conducted at temperatures ranging from 200 to 320 °C, with HZSM-5 demonstrating the highest catalytic activity. The study found that temperature and catalyst type significantly influenced product yields, with 2-methyl-2,3-dihydrobenzofuran being the primary product. The optimal reaction conditions were identified as 260 °C with an APE–water molar ratio of 1:40, yielding 65% of the desired product. The HZSM-5 catalyst showed high selectivity and recyclability, maintaining its activity over multiple uses. The study also tested various allyl phenyl ether derivatives, achieving high yields (83–95%) of corresponding dihydrobenzofurans.
10.1002/chem.200800210
The study explores the use of gold catalysis to synthesize various heterocycles, including chromans, dihydrobenzofurans, dihydroindoles, and tetrahydroquinolines. The researchers prepared furans containing ynamide or alkynyl ether moieties in the side chain and used gold-catalyzed transformations to achieve these syntheses at room temperature through fast reactions. The heteroatom directly attached to the intermediate arene oxides stabilized the intermediates, leading to highly selective reactions, even with mono-substituted furans. The study involved various chemicals, including lithiated furans for the introduction of side chains, oxiranes and enones for synthesis of alcohols, and dichlorovinyl ethers and toluenesulfonamides as starting points for ynamide syntheses. The gold-catalyzed reactions resulted in the formation of the desired heterocycles with good yields and selectivity, highlighting the efficiency and versatility of gold catalysis in organic synthesis.
