Abstract
This work reports the development of two catalytic cyclizations of 2-propenyl-1-ethynylbenzenes with aryldiazo esters. Cationic gold catalyst produces 2-substituted 3-alkenyl-1H-indenes with substrates over a reasonable scope. Our mechanistic study suggests that arydiazo esters attack at the cyclopropyl moieties of gold carbene intermediates, followed by skeletal rearrangement of resulting intermediates. In the presence of Rh 2 (esp) 2 additive, the same gold catalyst alters the chemoselectivity of these reactants to afford tetrahydro-1H-cyclopropa[b]naphthalenes with excellent stereoselectivity. Herein, Rh(II) catalyst catalyzed the reactions of the same 1,6-enynes with diazo species to form cyclopropenes initially, and a cationic Au(I) catalyst allows their subsequent reactions with the tethered alkenes. Preferable E-selectivity and synergistic effects of Au/Rh catalysts are rationalized in a postulated mechanism.