Construction of the Erythrinane Core Skeleton via Asymmetric Catalytic Cascade Reaction of Tertiary Enamides

Spokewise Total Syntheses of Four Erythrina Alkaloids and Telescoped Syntheses of Six Additional Alkaloids

Based on rich sulfur-involving chemical transformations, a novel spokewise synthetic strategy, a subclass of the collective strategies, has been developed to concisely synthesize four erythrina alkaloids through a single-step transformation from a common synthetic precursor. Moreover, six additional erythrina alkaloids have also been synthesized by subsequent 1-2 steps chemical transformations. The current synthetic approaches provide a valuable platform for collective total syntheses of erythrina alkaloids and pseudo-natural erythrina alkaloids.

Catalytic Asymmetric Polycyclization of Tertiary Enamides with Silyl Enol Ethers: Total Synthesis of (-)-Cephalocyclidin A

A catalytic enantioselective polycyclization of tertiary enamides with terminal silyl enol ethers has been developed by virtue of Cu(OTf)2 catalysis with a novel spiropyrroline-derived oxazole (SPDO) ligand. This tandem reaction offers an effective approach to assemble bicyclic and tricyclic N-heterocycles bearing both aza- and oxa-quaternary stereogenic centers, which are primal subunits in a range of natural alkaloids. Strategic application of this methodology and a late-stage radical cyclization as key steps have been showcased in the concise total synthesis of (-)-cephalocyclidin A.

Brønsted-Acid-Catalyzed In Situ Formation of Acyclic Tertiary Enamides and Its Application to the Preparation of Diverse Nitrogen-Containing Heterocyclic Compounds

A Brønsted acid-catalyzed cascade process, involving in situ formation of acyclic tertiary enamides and intramolecular Michael reaction, is developed for the synthesis of functionalized cyclic tertiary enamides. Based on the dual reactivities of the enamide moiety, several reaction sequences were realized by using rationally designed substrates, leading to biologically relevant nitrogen-containing heterocyclic compounds with diverse structural skeletons in a concise and diastereocontrolled manner.

Catalytic asymmetric de novo construction of 4-pyrrolin-2-ones via intermolecular formal [3+2] cycloaddition of azoalkenes with azlactones

The chiral phosphoric acid-catalyzed asymmetric intermolecular formal [3+2] cycloaddition of azoalkenes with azlactones has been established. This convergent protocol leads to a facile and enantioselective de novo construction of a wide range of fully substituted 4-pyrrolin-2-ones bearing a fully substituted carbon atom in good yields and with excellent enantioselectivities (26 examples, 72-95% yields and 87-99% ee).

Domino Reactions of Tertiary Enamides in Organic Synthesis

Studies in recent decade have shown that tertiary enamides, once thought of as unreactive and marginally useful enamine variants, are shelf-stable yet versatile nucleophilic intermediates in organic synthesis. Many compounds, especially N-heterocycles, have been synthesized by monofunctionalization reactions of tertiary enamides. By taking advantage of intramolecular and intermolecular interception of the putative acyliminium intermediates formed by the initial nucleophilic reactions of tertiary enamides, we have established several novel difunctionalization reaction methods for constructing diverse complex fused heterocyclic products. In this Account, we summarize our endeavors to develop difunctionalization reactions of tertiary enamides in a domino fashion.

1 Introduction

2 Strategic Considerations

3 Domino Reactions of Tertiary Enamides

3.1 Type I Domino Reactions

3.2 Type II Domino Reactions

3.3 Type III Domino Reactions

4 Conclusion and Perspectives

Catalytic enantioselective synthesis of indolizino[8,7-b]indole alkaloid derivatives based on the tandem reaction of tertiary enamides

An exquisite Pybox/Cu(OTf)₂-catalyzed asymmetric tandem reaction of tertiary enamides was developed, which enabled the expeditious synthesis of indolizino[8,7-b]indole derivatives in high yield, excellent enantioselectivity and diastereoselectivity.