Phosphine-Catalyzed Diastereoselective [3 + 3] Annulation of Morita-Baylis-Hillman Carbonates with C ,N -Cyclic Azomethine Imines

Phosphine-Catalyzed Cascade Annulation of MBH Carbonates and Diazenes: Synthesis of Hexahydrocyclopenta[c]pyrazole Derivatives

A phosphine-catalyzed cascade annulation of Morita-Baylis-Hillman (MBH) carbonates and diazenes was achieved, giving tetrahydropyrazole-fused heterocycles bearing two five-membered rings in moderate to excellent yields. The reaction underwent an unprecedented reaction mode of MBH carbonates, in which two molecules of MBH carbonates were fully merged into the ring system.

An overview of the reactions involving azomethine imines over half a decade

Azomethine imines constitute a versatile class of 1,3-dipoles which was used extensively for biologically relevant N-heterocycle synthesis – a five-year recap.

Phosphine-Promoted [4 + 3] Annulation of Allenoate with Aziridines for Synthesis of Tetrahydroazepines: Phosphine-Dependent [3 + 3] and [4 + 3] Pathways

In this manuscript, phosphine-dependent [3 + 3] and [4 + 3] annulation reactions of allenoate with aziridines were disclosed. The alkyldiphenylphosphine-promoted [4 + 3] annulation of allenoate with aziridines has been achieved under mild conditions, providing biologically interesting functionalized tetrahydroazepines in moderate to excellent yield with moderate to excellent regioselectivity and diastereoselectivity.

Phosphine-dependent [3 + 3] and [4 + 3] annulation reactions of allenoate with aziridines were disclosed. The alkyldiphenylphosphine-promoted [4 + 3] annulation produced tetrahydroazepines.

Phosphine Organocatalysis

The hallmark of nucleophilic phosphine catalysis is the initial nucleophilic addition of a phosphine to an electrophilic starting material, producing a reactive zwitterionic intermediate, generally under mild conditions. In this Review, we classify nucleophilic phosphine catalysis reactions in terms of their electrophilic components. In the majority of cases, these electrophiles possess carbon-carbon multiple bonds: alkenes (section 2), allenes (section 3), alkynes (section 4), and Morita-Baylis-Hillman (MBH) alcohol derivatives (MBHADs; section 5). Within each of these sections, the reactions are compiled based on the nature of the second starting material-nucleophiles, dinucleophiles, electrophiles, and electrophile-nucleophiles. Nucleophilic phosphine catalysis reactions that occur via the initial addition to starting materials that do not possess carbon-carbon multiple bonds are collated in section 6. Although not catalytic in the phosphine, the formation of ylides through the nucleophilic addition of phosphines to carbon-carbon multiple bond-containing compounds is intimately related to the catalysis and is discussed in section 7. Finally, section 8 compiles miscellaneous topics, including annulations of the Hüisgen zwitterion, phosphine-mediated reductions, iminophosphorane organocatalysis, and catalytic variants of classical phosphine oxide-generating reactions.