Rh(II) acetate catalyzed cyclopropanation of styrenes with enaldiazo esters: diastereoselective synthesis of enal-cyclopropanes

An efficient Rh(II) acetate catalyzed highly diastereoselective cyclopropanation of styrenes with enaldiazo esters has been developed (up to >95:5 dr and 62–82% yield). The reaction is proposed to involve diacceptor electrophilic rhodium enalcarbenoids and constitutes the first direct synthesis of enal-cyclopropanes with an all carbon γ-quaternary stereocenter.