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Herein, we have developed a method for the construction of spirobenzofuran-2,2'-bicyclo[2.1.1hexanes] via BF3·Et2O-catalyzed formal 2π + 2σ cycloaddition of bicyclo1.1.0butanes with benzofuran-derived oxa(aza)dienes. This transformation allowed for facile access to a variety of functionalized spiro-bicyclo2.1.1hexanes in good yields (up to 99% yield) with excellent regioselectivities and a broad substrate scope (34 examples) under mild reaction conditions. Moreover, the synthetic utility of the cycloadducts were further emphasized through a scale-up experiment and subsequent synthetic transformations.
Su et al. (Thu,) studied this question.