Visible Light‐Induced [3+2] Cyclization Reactions of Hydrazones with Hypervalent Iodine Diazo Reagents for the Synthesis of 1‐Amino‐1,2,3‐Triazoles

Abstract

In this study, visible‐light‐induced [3+2] cyclization reactions of hydrazones with hypervalent iodine diazo reagents as diazomethyl radical precursors are reported. Mild reaction conditions, a broad substrate scope, and excellent functional group compatibility were observed. Furthermore, the synthetic utility was demonstrated by gram‐scale synthesis and elaboration to several value‐added products. This protocol broadens the scope of diazo chemistry, and is applicable to the late‐stage functionalization of natural products.

Visible Light-Induced Coupling Cyclization Reaction of α-Diazosulfonium Triflates with α-Oxocarboxylic Acids or Alkynes

“…These results indicate that DCM or CD 3 CN act as the hydrogen atom source to provide hydrogen radical for the formation of intermediate H from intermediate G (Scheme 3). On the basis of the mechanistic investigations and related literatures, [5][6][7][8][9][10][11]16 a plausible reaction mechanism for the formation of compounds 3 and 5 is proposed in Scheme 3. Initially, diazomethyl radical A and cation radical B are generated from α-diazosulfonium triflates 1 under the irradiation of blue light via homolytic S−C bond cleavage.…”

Synthesis of [1,2,3]Triazolo-[1,5-a]quinoxalin-4(5H)-ones through Photoredox-Catalyzed [3 + 2] Cyclization Reactions with Hypervalent Iodine(III) Reagents

“…Hypervalent iodine­(III) reagent 2a – 2d were prepared according to the previously reported literature procedures. , …”

“…Recently, a visible-light-induced [3 + 2] cyclization reaction of hydrazones with hypervalent iodine diazo reagents has been reported to synthesize 1-amino-1,2,3-triazoles by Li and Wang . Inspired by our catalytic photoredox synthesis of 2,5-disubstituted 1,3,4-oxadiazoles derivatives by a cyclization reaction between α-oxocarboxylic acids/aldehydes and a hypervalent iodine­(III) reagent, we expect to construct a 1,2,3-triazole fused heterocyclic skeleton through [3 + 2] cycloaddition with hypervalent iodine diazo reagents and imine via the [3 + 2] cyclization.…”

Generation of Diazomethyl Radicals by Hydrogen Atom Abstraction and Their Cycloaddition with Alkenes

“…Recently, the Suero group, as well as the Alcarazo group reported the generation of a diazomethyl radical through the photoredox single electron transfer (SET) process (Scheme 1 b). [10] The diazo moiety could be transferred to either aromatic rings or hydrazones utilizing hypervalent I(III) [10a–d] or sulfonium ions [10e] as the leaving group. Since the electronic characteristics of the diazo group could be reversed from nucleophilic to electrophilic through the formation of the diazomethyl radical, [10a, 11] we considered whether electron‐neutral or even electron‐rich alkenes could be incorporated with the diazocarbon radical intermediate utilizing this umpolung strategy, [12] thereby providing a general methodology that would provide an alternative strategy for cycloaddition of alkenes that are unreactive towards dipolar cycloaddition.…”