Brönsted acid catalyzed addition of N 1 - p -methyl toluenesulfonyl triazole to olefins for the preparation of N 2 -alkyl 1,2,3-triazoles with high N 2 -selectivity

Regioselectively Electrochemical Synthesis of N2-Selective C-H Amination of Ethers with N-Tosyl 1,2,3-Triazole via Triazole Radical Cation

A regioselective electrochemical C-H amination method to synthesize N²-substituted 1,2,3-triazole using easily accessible ethers has been developed. Various substituents, including heterocycles, have a good tolerance, and 24 examples were obtained in moderate to good yields. Control experiments and DFT calculation investigations demonstrate that the electrochemical synthesis undergoes a N-tosyl 1,2,3-triazole radical cation process promoted by the single-electron transfer of the lone pair electrons of the aromatic N-heterocycle, and the desulfonation is responsible for the high N²-regioselectivity.

N2-Selective β-Thioalkylation of Benzotriazoles with Alkenes

Herein, N²-selective β-thioalkylation of benzotriazoles with unactivated alkenes and styrenes is reported. The N²-selective β-thioalkylation of benzotriazoles is highly stereospecific and works under simple and mild conditions, exhibiting excellent functional group tolerance. The high N²-selectivity is a consequence of the combination of hydrogen bonding and Lewis acid/base activation, which reverses the N²-position to be favored for alkylation.

Recent Developments in N2-Selective Functionalizations of 1,2,3-Triazoles

The widespread use of 1,2,3-triazole compounds in drugs has resulted in a great interest in the efficient synthesis of N2-substituted 1,2,3-triazoles via post triazole functionalization methods. At present, there are many methods for the synthesis of N1-substituted 1,2,3-triazole compounds, but the development of convenient methods for the N2-selective functionalization of 1,2,3-triazoles remains challenging. In general, the greater stability of the N1 tautomer makes the N2 position a non-preferable reactive site, which has limited the application of 1,2,3-triazoles. In this review, we summarized advances in the direct N2-selective functionalization of 1,2,3-triazoles since 2008.

1 Introduction

2 N2-Alkylation

3 N2-Allylation

4 N2-Propargylation

5 N2-Alkenylation

6 N2-Alkynylation

7 N2-Arylation

8 Conclusions and Outlook

Base-Induced Highly Regioselective Synthesis of N2-Substituted 1,2,3-Triazoles under Mild Conditions in Air

We developed a highly regioselective base-induced synthesis of N²-substituted 1,2,3-triazoles from N-sulfonyl-1,2,3-triazoles and alkyl bromides/alkyl iodides at room temperature. We propose an S_N2-like mechanistic pathway to explain the high N²-regioselectivity. The protocol features a broad substrate scope and generates products in good to excellent yields (72-90%).

Diamine-mediated N2-selective β-selenoalkylation of triazoles with alkenes

A N2-selective β-selenoalkylation of 1,2,3-triazoles with alkenes mediated by diamines has been developed. The reaction proceeds presumably via the interaction of diamines with both the triazole moiety and selenium/alkene complex to construct a U-shaped reaction intermediate. This activation mode will block the N1 position on triazoles and thus favor the N2-selective selenoamination. This stereospecific anti-addition method enables an efficient N2-selective β-selenoalkylation of 1,2,3-triazoles under mild and open-air conditions and might find applications in the synthesis of biologically active molecules.

Regioselective N1- and N2-heterocycloalkylation of N1-sulfonyl-1,2,3-triazoles

A tuneable and visible-light-driven three-component reaction between N¹-sulfonyl-1,2,3-triazoles, saturated heterocycles, and N-bromosuccinimide for regioselective synthesis of N¹- or N²-heterocycloalkylated 1,2,3-triazoles.

Highly N2-selective allylation of NH-1,2,3-triazoles with allenamides mediated by N-iodosuccinimide

We report a new protocol to synthesize N²-allyl-substituted 1,2,3-triazoles via NIS mediated allylation of allenamides with NH-1,2,3-triazoles.

N-2-Selective gold-catalyzed alkylation of 1-sulfonyl-1,2,3-trizoles

An efficient new method was developed to synthesis N-2-alkyl-1,2,3-trizoles via gold catalyzed alkylation of 1-sulfonyl-1,2,3-trizoles with vinyl ethers.

Post-synthetic modification of tryptophan containing peptides via NIS mediation

A new method to provide modified tryptophan peptides through NIS mediated N²-selective coupling of a Trp unit with 1,2,3-triazoles, of which, the preliminary spectral properties were studied.