Catalytic asymmetric de novo construction of 4-pyrrolin-2-ones via intermolecular formal [3+2] cycloaddition of azoalkenes with azlactones.

The chiral phosphoric acid-catalyzed asymmetric intermolecular formal [3+2] cycloaddition of azoalkenes with azlactones has been established. This convergent protocol leads to a facile and enantioselective de novo construction of a wide range of fully substituted 4-pyrrolin-2-ones bearing a fully substituted carbon atom in good yields and with excellent enantioselectivities (26 examples, 72-95% yields and 87-99% ee).

Catalytic asymmetric inverse-electron-demand aza-Diels-Alder reaction of 1,3-diazadienes with 3-vinylindoles.

A facile chiral phosphoric-acid catalyzed asymmetric inverse-electron-demand aza-Diels-Alder reaction of 1,3-diazadienes with 3-vinylindoles was established. By using this mild and practical protocol, a broad range of benzothiazolopyrimidines with three contiguous stereogenic centers were prepared in good yields and excellent diastereo- and enantio-selectivities (43 examples, up to 83% yield, >99% ee and all >20 : 1 dr). A plausible concerted reaction pathway enabled by the dual hydrogen-bonding effect was proposed to account for the observed excellent enantioselectivity and specific trans-trans diastereoselectivity.