Catalytic asymmetric [3+2] cycloaddition of isomünchnones with methyleneindolinones

Metal-Free Regioselective Oxa-Michael Approach to Access Spirooxindole-Fused Tetrahydrofuran/Tetrahydropyran through [3 + 2]/ [4 + 2] Spirocyclization of Methyleneindolinones with Haloalcohols

An efficient one-pot metal-free, base-catalyzed method has been developed for the regioselective [3 + 2]/[4 + 2] annulation reactions of electrophilic methyleneindolinones with haloalcohols to furnish spirooxindole derivatives under mild reaction conditions. This reaction afforded the corresponding products with two contiguous stereocenters including a quaternary center in good to excellent yield (up to 95%) with moderate to good diastereoselectivities (up to 12.5:1 dr) with complete regioselectivity.

Cooperative Rh/Achiral Phosphoric Acid-Enabled [3+3] Cycloannulation of Carbonyl Ylides with Quinone Monoimines: Synthesis of Benzofused Dioxabicyclo[3.2.1]octane Scaffolds

A cooperative Rh/achiral phosphoric acid-enabled [3+3] cycloaddition of in situ-generated carbonyl ylides with quinone monoimines has been developed. With the ability to build up the molecular complexity rapidly and efficiently, this method furnishes highly functionalized oxa-bridged benzofused dioxabicyclo[3.2.1]octane scaffolds bearing two quaternary centers in good to excellent yields under mild conditions. Moreover, the utility of the current method was demonstrated by gram-scale synthesis and elaboration of the products into various functionalized oxa-bridged heterocycles.

Diastereoselective Cascade Cyclization of Diazoimides with Alkylidene Pyrazolones for Preparation of Pyrazole-Fused Oxa-Bridged Oxazocines

Under the catalysis of Rh2(OAc)4 (10 mol%) and binapbisphosphine ligand (±)-L3 (20 mol%) in DCE at 80 °C, the cascade cyclization of diazoimides with alkylidenepyrazolones underwent stereoselectively (dr > 20:1), affording pyrazole-fused oxa-bridged oxazocines in reasonable chemical yields. The chemical structure and relative configuration of title products were firmly identified by X-ray diffraction analysis.