Erqing Li

Phosphine-Catalyzed [4 + 2] Annulation of γ-Substituent Allenoates: Facile Access to Functionalized Spirocyclic Skeletons

The first phosphine-catalyzed [4 + 2] annulation of γ-substituted allenoates with 2-arylidene-1H-indene-1,3(2H)-diones is disclosed. In the reaction, the γ-substituted allenoate serves as a new type of 1,4-dipolar synthon; this broadens the application of γ-substituted allenoates. This method also offers a powerful approach to the construction of highly substituted spiro[4.5]dec-6-ene skeletons in excellent yields, and with complete regioselectivity and high diastereoselectivity.

Highly Enantioselective Intermolecular Cross Rauhut–Currier Reaction Catalyzed by a Multifunctional Lewis Base Catalyst†

The highly enantioselective intermolecular cross Rauhut-Currier reaction of different active olefins catalyzed by a multifunctional chiral Lewis base was reported. The RC products were obtained in excellent yields (up to 98 %), high chemo- and enantioselectivity (up to 96 % ee). The reaction could be performed on a gram scale using 1 mol % of the multifunctional phosphine catalyst.

Domino Reaction for the Chemo- and Stereoselective Synthesis of trans-2,3-Dihydrobenzofurans from N-Thiophosphinyl Imines and Sulfur Ylides

A novel domino annulation between sulfur ylides and salicyl N-thiophosphinyl imines was developed. The method allows the synthesis of a highly substituted trans-2,3-dihydrobenzofuran skeleton with high yield and excellent chemo- and stereoselectivity.

Bifunctional-Phosphine-Catalyzed Sequential Annulations of Allenoates and Ketimines: Construction of Functionalized Poly-heterocycle Rings

A highly stereoselective sequential annulation reaction between γ-substituted allenoates and ketimines was reported. By using bifunctional N-acyl aminophosphine catalysts, poly-heterocycle rings were obtained with high stereocontrol in good to excellent yields. The desired products have four contiguous stereogenic centers (one quaternary and three tertiary carbon centers), and only one isomer was obtained in all reactions.

Phosphine‐Initiated Domino Reaction: A Convenient Method for the Preparation of Spirocyclopentanones

An efficient synthetic approach has been developed for the construction of the spirocyclopentanone skeleton via a phosphine-catalyzed [3+2] annulation reaction. With this novel and economical protocol, various quaternary carbon-centered spirocyclopentanones could be readily obtained.

Tuning catalysts to tune the products: phosphine-catalyzed aza-Michael addition reaction of hydrazones with allenoates.

A new tunable phosphine-catalyzed aza-Michael β-addition reaction between allenoates and various hydrazones has been developed. These reactions are most-efficiently promoted by a catalytic amount of phosphine catalysts. These atom-economical reactions are operationally simple and their corresponding adducts can been achieved in high yields and high selectivity under mild reaction conditions. Further studies revealed that different phosphine catalyst can produce different adducts from the same starting materials.

DABCO-Mediated [4 + 4]-Domino Annulation: Access to Functionalized Eight-Membered Cyclic Ethers

DABCO-mediated [4 + 4] domino annulation reactions of ynones and α-cyano-α,β-unsaturated ketones were discovered. The domino process affords an alternative route to eight-membered cyclic ethers in good yields under mild conditions.

Divergent synthesis of hydropyridine derivatives via nitrogen-containing Lewis base mediated regioselective [4 + 2] cyclizations

A nitrogen-containing Lewis base mediated regioselective [4 + 2] cyclization strategy between allenic esters and α,β-unsaturated ketimines was discovered, affording a series of hydropyridine derivatives in moderate to good yields under mild conditions.