Construction of Oxo-Bridged Diazocines via Rhodium-Catalyzed (4+3) Cycloaddition of Carbonyl Ylides with Azoalkenes

Sc(OTf)3-Catalyzed Precise Construction of Medium-Sized [4.2.1]-Oxabridged Scaffolds

In this study, the readily available and inexpensive Sc(OTf)3 was utilized to activate ortho-benzoyl diazo compounds to in situ generate highly reactive cyclic 1,3-dipoles, which underwent a regioselective [4 + 3] cycloaddition with dioxopyrrolidines, yielding the [4.2.1]-oxabridged scaffolds bearing multiple contiguous quaternary carbon centers with high diastereoselectivities. The method not only exhibited significant economic and operational advantages but also demonstrated practical value through gram-scale synthesis and derivatization experiments.

Expedient (3+3)-annulation of carbonyl ylides with azaoxyallyl cations: formal access to oxa-benzo[c]azepin-3-ones

The cascade carbon-carbon and carbon-nitrogen bond formation between in situ generated carbonyl ylides and azaoxyallyl cations, facilitated by Rh-catalysis and a base, has been achieved to furnish oxa-benzo[c]azepin-3-ones. Substrate scope, functional group diversity, scale-up and post-synthetic utilities are the important practical features.

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.

Construction of 3,4-Dihydroquinolone Derivatives through Pd-Catalyzed [4+2] Cycloaddition of Vinyl Benzoxazinanones with α-Alkylidene Succinimides

The construction of 3,4-dihydroquinolone derivatives has attracted a considerable amount of attention due to their extensive applications in medicinal chemistry. In this study, we present the Pd-catalyzed [4+2] cycloaddition of vinyl benzoxazinanones with α-alkylidene succinimides for the efficient synthesis of 3,4-dihydroquinolones. This approach presents numerous advantages, including the ready availability of starting materials, mild reaction conditions without the use of additional bases, and a wide range of substrates. In particular, all of the desired products can be easily afforded in high yields (≤99%) and excellent diastereoselectivities (>20:1). The practicality and reliability of this strategy were demonstrated by the successful scale-up synthesis and subsequent straightforward synthetic transformations.