Synthesis of Pyrrolidine- and γ-Lactam-Containing Natural Products and Related Compounds from Pyrrole Scaffolds

Nickel-catalysed reductive C-N bond cross-coupling between aryl halides and N-chloroamides

A method for the direct synthesis of N-aryl lactams and amides with aryl halides and N-chloroamides through a Ni-catalyzed reductive C-N coupling reaction has been developed. The reaction features the advantages of mild conditions, good functional group tolerance and broad substrate scope including drug-derived substrates, and also provided direct access to the key synthetic intermediates for some bioactive molecules, suggesting the practicability of this method. Finally, DFT calculations were performed to shed further light on the reaction mechanism and it was found that an amidyl radical might be involved.

Zn(II)-catalyzed asymmetric [3 + 2] cycloaddition of acyclic enones with azomethine ylides

The Zn(II)/UCD-Imphanol-catalyzed highly endo-selective [3 + 2] asymmetric cycloaddition of acyclic enones and azomethine ylides has been developed. Moderate to high yields (up to 94%) with excellent endo/exo selectivities (99 : 1) and enantioselectivities up to 96.5 : 3.5 er were obtained.

Enantioselective, Bro̷nsted Acid-Catalyzed Anti-selective Hydroamination of Alkenes

Chiral pyrrolidines are common structural motives in natural products as well as active pharmaceutical ingredients, explaining the need for methods for their enantioselective synthesis. While several, often metal-catalyzed, methods for their preparation do exist, the enantioselective synthesis of pyrrolidines containing quaternary stereocenters remains challenging. Herein, we report a Bro̷nsted acid-catalyzed intramolecular hydroamination that provides such pyrrolidines from simple starting materials in high yield and enantioselectivity. Key to an efficient reaction was the use of an electron-deficient protective group on nitrogen, the common nosyl-protecting group, to avoid deactivation of the Bro̷nsted acid by deprotonation. The reaction proceeds as a stereospecific anti-addition indicating a concerted reaction. Furthermore, kinetic studies show Michaelis-Menten behavior, suggesting the formation of a precomplex similar to those observed in enzymatic catalysis.

Dual Photoredox/Nickel Catalysis Enables Diastereoselective Synthesis of Multisubstituted γ-Lactams Using Alkyl-GeMe3 as Radical Precursors

Herein, we report a single-step, multicomponent approach to versatile γ-lactams through dual photoredox/nickel-catalyzed dicarbofunctionalization of α,β-unsaturated γ-butyrolactam. This reaction utilized alkyl trimethylgermanium as a radical precursor and acyl chloride as the electrophile, demonstrating remarkable functional group compatibility.

One-Pot, Tandem Reductive Amination/Alkylation-Cycloamidation for Lactam Synthesis from Keto or Amino Acids

Monotrifluoroacetoxyborane-amines, prepared by treating borane-amines with trifluoroacetic acid, have been shown to be efficient reagents for a one-pot, tandem reductive amination/alkylation-cycloamidation of keto or amino acids to achieve the synthesis of 5-aryl or 5-methyl pyrrolidin-2-ones and 6-aryl or 6-methyl piperidin-2-ones.

3-Trifluoromethyl Pyrrole Synthesis Based on β-CF3-1,3-Enynamides

A new metal-free method for the rapid, productive, and scalable preparation of 3-trifluoromethyl pyrroles has been developed. It is based on the electrophilic nature of the double bond of β-CF3-1,3-enynamides due to the electron-withdrawing characteristics of the trifluoromethyl groups and the strong nucleophilic nature of alkyl primary amines. Evidence for the highly regioselective 1,4-hydroamination was observed after the isolation and characterization of the allenamide intermediate.

Recent Advances in [3+2]-Cycloaddition-Enabled Cascade Reactions: Application to Synthesize Complex Organic Frameworks

Many natural products and biologically important complex organic scaffolds have convoluted structures around their core skeleton. Interestingly, with just changing the outskirts, the core reflects new and unique degrees of various physical and chemical properties. A very common but intriguing core is a five-membered ring horning heaps of organic molecules crafts. The power of [3+2] cycloaddition reactions to generate five-membered ring systems allocate chemists to envision synthetic procedures of wonder molecules and if it is facilitating a cascade sequence, then the end product will imbibe significant level of complexity having applications in medicinal and pharmaceutical fields. This Account highlights the broad interest in assembling recent advances in cascade reactions involving [3+2] cycloaddition as the power tool in order to conceive breakthrough organic architectures reported in the last ten years. We foresee that our comprehensive collection of astonishing [3+2] cycloaddition enabled cascades will provide valuable insights to polycyclic molecular construction and perseverant approach towards nonconventional synthetic procedures to the organic community.

1 Introduction

2 Synthesis of Oxindoles Skeleton

3 Synthesis of Oxazoles Skeleton

4 Synthesis of Oxadiazoles Skeleton

5 Synthesis of Nitrogen-Containing Heterocycles

6 Synthesis via Formal [3+2] Cycloaddition

7 Synthesis of Miscellaneous Scaffolds

8 Conclusion

Discovery of Periodinane Oxy-Assisted (POA) Oxidation Mechanism in the IBX-Controlled Oxidative Dearomatization of Pyrroles Mediated by Acetic Acid

The 2-iodoxybenzoic acid (IBX)-controlled oxidative dearomatization of pyrroles occurs very slowly (or not all) in many organic solvents, including DMSO in which IBX is soluble. Interestingly, although IBX is only partially soluble in acetic acid, this solvent mediates the pyrrole oxidative dearomatization. With the aid of density functional theory (DFT) calculations, we have discovered a new mode of reactivity, termed the periodinane oxy-assisted (POA) oxidation mechanism, which explains this observation.