A Ring ExpansionStereoselective Cycloaddition of Carbohydrate-Derived Donor–Acceptor Cyclopropanes: Synthesis of Bridged Oxepanone–Indole Hybrids

An efficient method for the construction of sugar-derived chiral oxepanone–indole molecular hybrids is investigated. The reaction condition is optimized by monitoring the progress at various temperatures, with various solvents, and with different Lewis acid catalysts. Under optimized conditions, high stereoselectivity and efficiency are achieved in most of the formed cycloadducts. The accessibility of the strategy is evaluated by utilizing an array of carbohydrate-derived donor–acceptor cyclopropanes and variably substituted indole substrates. Additionally, quick access to the bridged indole–oxepanone framework is described by utilizing a diastereoselective (3+2) cycloaddition of aryl-substituted donor–acceptor cyclopropanes incorporated in a pyran ring.