Zhengjie He

Phosphine-Catalyzed [4+1] Annulation between α,β-Unsaturated Imines and Allylic Carbonates: Synthesis of 2-Pyrrolines

In this report, a phosphine-catalyzed [4 + 1] annulation between α,β-unsaturated imines and allylic carbonates is described. This reaction represents the first realization of catalytic [4 + 1] cyclization of 1,3-azadienes with in situ formed phosphorus ylides, which provides highly efficient and diastereoselective synthesis of 2-pyrrolines.

Phosphine-catalyzed cascade [3 + 2] cyclization-allylic alkylation, [2 + 2 + 1] annulation, and [3 + 2] cyclization reactions between allylic carbonates and enones.

The phosphine-catalyzed annulations between Morita-Baylis-Hillman adduct carbonates and enones are reported. Under the catalysis of PBu(3) (20 mol %), cascade [3 + 2] cyclization-allylic alkylation, [2 + 2 + 1] annulation, and [3 + 2] cyclization reactions chemoselectively occur depending on the substituent variation of both the carbonate and enone. These reactions provide efficient syntheses of highly functionalized cyclopentenes and cyclopentanes.

Wittig olefination between phosphine, aldehyde, and allylic carbonate: a general method for stereoselective synthesis of trisubstituted 1,3-dienes with highly variable substituents.

A clean and salt-free Wittig olefination between phosphines, aldehydes, and allylic carbonates is described. It represents a general method for convenient and efficient synthesis of 1,2,4-trisubstituted 1,3-dienes from readily available starting materials. This method exhibits high synthetic efficiency, high stereoselectivity, and high variability of substituent.

Phosphine-Mediated Stereoselective Reductive Cyclopropanation of α-Substituted Allenoates with Aromatic Aldehydes

A novel phosphine-mediated reductive cyclopropanation between alpha-substituted allenoates 2 and aldehydes 1 is described. It represents a new member of the allene-based annulations, which provides facile and efficient access to highly functionalized cyclopropanes 3 from simple and readily available starting materials. It also unveils an unprecedented reactivity pattern of allenoates with aldehydes.

Recent advances in stoichiometric phosphine-mediated organic synthetic reactions

Organic synthetic reactions mediated by tertiary phosphines have attracted much attention in the organic chemistry community in the past two decades. These reactions can be divided into two categories: phosphine-catalyzed and stoichiometric phosphine-mediated transformations. While the phosphine-catalyzed reactions mechanistically rely on the unique properties of tertiary phosphines such as excellent nucleophilicity and good leaving group ability, the stoichiometric transformations are usually driven by nucleophilicity and strong oxyphilicity of tertiary phosphines. Since tertiary phosphines represent an important class of versatile chemical reagents in organic synthesis, stoichiometric phosphine-mediated reactions have recently demonstrated their uniqueness and high efficiency in organic synthesis, particularly with respect to the construction of carbon–carbon and carbon–heteroatom bonds, and therefore have stimulated much research interest. In this review, recent advances in stoichiometric phosphine-mediated reactions primarily including olefinations and annulations are summarized.

Phosphine-mediated olefination between aldehydes and allenes: an efficient synthesis of trisubstituted 1,3-dienes with high E-selectivity.

The phosphine-mediated olefination of aldehydes with electron-deficient allenes to afford trisubstituted conjugated dienes in fair to excellent yields with high E-selectivity is described. The reaction represents a new reactivity pattern of allenes with aldehydes and also provides a highly stereoselective synthetic method for preparing conjugated dienes. In the reaction, the phosphine acts as a nucleophilic promoter to generate in situ an active phosphorus ylide which mediates the intermolecular olefination.

Stereoselective Synthesis of 1,2,3,4-Tetrasubstituted Dienes from Allenoates and Aldehydes: An Observation of Phosphine-Induced Chemoselectivity

Phosphine-mediated olefination between alpha-substituted allenoates and aldehydes to form 1,2,3,4-tetrasubstituted 1,3-dienes is presented. High levels of chemo- and diastereoselectivity and yield are obtained for a wide scope of substrates with the choice of appropriate phosphines. This reaction evidences the capacity of phosphines in the control of reaction pathways and provides a highly efficient synthetic method for tetrasubstituted conjugated dienes.

Diastereoselective synthesis of functionalized spirocyclopropyl oxindoles via P(NMe2)3-mediated reductive cyclopropanation.

A P(NMe2)3-mediated reductive cyclopropanation reaction of α-keto esters or amides with isatin-derived alkenes has been developed, providing efficient and diastereoselective synthesis of highly functionalized spirocyclopropyl oxindoles bearing two all-carbon quaternary centers. This reaction also represents a complementary and nonmetal-involving protocol for the challenging cyclopropanation of electron-deficient alkenes.

Phosphine-triggered tandem annulation between Morita-Baylis-Hillman carbonates and dinucleophiles: facile syntheses of oxazepanes, thiazepanes, and diazepanes.

A new phosphine-triggered tandem [3 + 4] annulation reaction between Morita-Baylis-Hillman carbonates and 1,4-diheteroatom dinucleophiles has been developed, which provides a facile synthetic method for saturated seven-membered 1,4-heterocycles such as 1,4-oxazepanes, 1,4-thiazepanes, and 1,4-diazepanes. Mechanistic investigation implies that this reaction takes place through a phosphine-catalyzed allylic alkylation followed by a general base-catalyzed intramolecular Michael cyclization.

Highly Chemoselective Rauhut–Currier Reaction between Maleimides and Enones and Dual Phosphine-Mediated One-Pot Synthesis of Bicyclic and Polycyclic Skeletons

A highly chemoselective phosphine-catalyzed Rauhut-Currier reaction between maleimides and enones has been realized under very mild conditions, affording the corresponding cross-coupling products in moderate to excellent yields. On the basis of this reaction, an efficient dual phosphine-mediated one-pot synthesis of bicyclic and polycyclic compounds containing a cyclopenta[c]pyrrole skeleton has been accordingly developed, which features a tandem sequence of intermolecular Rauhut-Currier reaction and intramolecular Wittig reaction.