Copper-catalyzed [3 + 2]-cycloaddition of α-halonitroalkenes with azomethine ylides: facile synthesis of multisubstituted pyrrolidines and pyrroles

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.

Regioselective Synthesis of Highly Functionalized 2H-Pyrroles via Dearomative Chlorination of 1H-Pyrroles

An efficient protocol was developed for the synthesis of highly functionalized 2H-pyrroles. This synthetic approach involves the in situ generation of highly reactive 2,5-dichloro-substituted 2H-pyrroles through dearomative chlorination of the corresponding 1H-pyrroles. The resulting reaction mixture is then treated with various amines, leading to the formation of 2,5-diaminated 2H-pyrroles. Subsequent nucleophilic substitution of fluorine with different N-, O-, and S-nucleophiles allows us to introduce additional functionality into a 2H-pyrrole core. The overall outcome of this reaction sequence is the triple nucleophilic modification of pyrroles. All steps of the sequence were found to be highly efficient, regioselective in the preparation of desired di- and trisubstituted derivatives in up to 96% overall yield. In addition, the computational study of this reaction sequence was carried out using density functional theory (DFT). The results of calculations are in perfect agreement with experimental observations.

Enal-azomethine ylides: application in the synthesis of functionalized pyrroles

Rhodium-catalyzed [3 + 2] annulation of diazoenals and N-alkyl imines resulted in N-alkyl-pyrrole-3-carbaldehyde derivatives. The reaction involves thermal 6π-electrocyclization and aromatization of a new class of enal-azomethine ylides (EAYs). The EAYs derived from dihydroisoquinoline and 2H-azirine gave fused-pyrrole and pyridine derivatives, respectively. The synthetic importance of pyrrole products has been demonstrated by one-step synthesis of the biologically relevant pyrrolo[3,2-c]quinoline scaffold as well as pyrrolo[2,1-a]isoquinoline which is a core structure of lamellarin alkaloids.

Electron-rich benzofulvenes as effective dipolarophiles in copper(i)-catalyzed asymmetric 1,3-dipolar cycloaddition of azomethine ylides

A series of benzofulvenes without any electron-withdrawing substituents were employed as 2π-type dipolarophiles for the first time to participate in Cu(i)-catalyzed asymmetric 1,3-dipolar cycloaddition (1,3-DC) reactions of azomethine ylides. An intrinsic non-benzenoid aromatic characteristic from benzofulvenes serves as a key driving force for activation of the electron-rich benzofulvenes. Utilizing the current methodology, a wide range of multi-substituted chiral spiro-pyrrolidine derivatives containing two contiguous all-carbon quaternary centers were formed in good yield with exclusive chemo-/regioselectivity and high to excellent stereoselectivity. Computational mechanistic studies elucidate the origin of the stereochemical outcome and the chemoselectivity, in which the thermostability of these cycloaddition products is the major factor.

DBU Promoted Polysubstituted Arene Formation via a Michael Addition/Cyclization/Elimination Cascade Reaction

The straightforward construction of polysubstituted arenes is essential in both synthetic chemistry and medicinal chemistry. Herein, we reported a DBU promoted Michael addition/cyclization/elimination cascade reaction between vinylogous malononitrile derivatives and chlorinated nitrostyrenes for the synthesis of polysubstituted arenes. The method features mild reaction conditions, wide substrate scope and high yield. Interestingly, preliminary study of the enantioselective version of this cascade was conducted to give chiral biaryl atropisomers with up to 40% ee through center-to-axial chirality transfer strategy.

Three-Component [3+2] Cycloaddition for Regio- and Diastereoselective Synthesis of Spirooxindole-Pyrrolidines

1,3-Dipolar cycloaddition of nonstabilized azomethine ylides derived from α-C-H functionalization of tetrahydroisoquinoline for regio- and diastereoselective synthesis of spirooxindole-pyrrolidines is developed. A three-component reaction of readily available cyclic amine, aryl aldehydes, and olefinic oxindoles provides a pot, atom and step economy (PASE) approach for making spiro-heterocyclic compounds with biological interest.

The Synthesis of Five-Membered N-Heterocycles by Cycloaddition of Nitroalkenes with (In)Organic Azides and Other 1,3-Dipoles

Cycloaddition reactions have emerged as rapid and powerful methods for constructing heterocycles and carbocycles. [3+2] Cyclo­additions of nitroalkenes with various 1,3-dipoles have been an interesting research area for many organic chemists. This review outlines the synthesis of N-substituted and NH-1,2,3-triazoles along with other five-membered N-heterocycles through cycloaddition reactions of nitro­alkenes.

1 Introduction

2 Synthesis of 1,2,3-Triazoles

2.1 Synthesis of NH-1,2,3-Triazoles

2.2 Synthesis of N-Substituted 1,2,3-Triazoles

3 Synthesis of Pyrrolidines and Pyrroles

4 Synthesis of Pyrazoles

5 Conclusion

Tandem Michael addition/elimination – novel reactivity of pyridinium ylides in reaction with electron-deficient alkenes

Novel reactivity of pyridinium ylides in reaction with 4-oxothiazolidin-5-ylidenes as electron-deficient alkenes involving a tandem Michael addition/elimination process was developed to give double bond functionalization products in mild conditions.

Oxidative [3+2]-annulation of nitroalkenes and azolium ylides in the presence of Cu(II): efficient synthesis of [5,5]-annulated N-fused heterocycles

A facile synthesis of [5,5]-annulated N-fused heterocycles – pyrrolo[2,1-b]thiazoles and pyrrolo[1,2-b]indazoles via oxidative [3+2]-annulation between nitroalkenes and azolium ylides in the presence of copper (II) was developed. The reaction proceeds...