Sulfuryl Fluoride Mediated Synthesis of Amides and Amidines from Ketoximes via Beckmann Rearrangement

Recent approaches for the synthesis of heterocycles from amidines via a metal catalyzed C-H functionalization reaction

Transition metal catalyzed C-H bond activation has become one of the most important tools for constructing new chemical bonds. Introducing directing groups to the substrates is the key to a successful reaction, these directing groups can also be further transformed in the reaction. Amidines with their unique structure and reactivity are ideal substrates for transition metal-catalyzed C-H transformations. This review describes the major advances and mechanistic investigations of the C-H activation/annulation tandem reactions of amidines until early 2024, focusing on metal-catalyzed C-H activation of amidines with unsaturated compounds, such as alkynes, ketone, vinylene carbonate, cyclopropanols and their derivatives. Meanwhile this manuscript also explores the reaction of amidines with different carbene precursors, for example diazo compounds, azide, triazoles, pyriodotriazoles, and sulfoxonium ylides as well as their own C-H bond activation/cyclization reactions. A bright outlook is provided at the end of the manuscript.

A modified Beckmann rearrangement for the facile synthesis of amidines and imidates via imidoyl fluoride intermediates

Herein, we report a modified Beckmann rearrangement using sulfone iminium fluoride (SIF) reagents to rapidly synthesize imidoyl fluoride intermediates. Subsequently, amidine and imidate products can be formed following the introduction of amine and alcohol nucleophiles, respectively. Overall, approximately 50 amidine and imidate products have been isolated in high yields utilizing mild conditions.

The stable "F-SO2 +" donor provides a mild and efficient approach to nitriles and amides

In this update, we developed a mild, efficient and practical method using fluorosulfuryl imidazolium salt A as an environment friendly promoter for conversion of oximes to nitriles or amides via β-elimination or Beckmann rearrangement in almost quantitative yield in 10 minutes. The target products were generated in gram-scale and could be collected through crystallization without silica gel column purification in excellent yield.

Synthesis of α-Ketoimidoyl Fluorides via Geminal Fluorine-Promoted Azide Rearrangement

Despite the promising synthetic potential, the utilization of imidoyl fluorides has been hampered by the lack of broadly applicable preparative methods. Herein, bench-stable α-ketoimidoyl fluorides were synthesized from geminal chlorofluorides through tandem azidation/rearrangement under mild conditions. The efficiency was consistently high, regardless of the steric and electronic environments. The synthetic utility of the α-ketoimidoyl fluoride was also demonstrated. Furthermore, the remarkable accelerating effect of the geminal fluorine substituent was identified and rationalized by density functional theory calculation.

The serendipitous effect of KF in Ritter reaction: Photo-induced amino-alkylation of alkenes

Ritter reaction has been recognized as an elegant strategy to construct the C−N bond. Its key feature is forming the carbocation for nucleophilic attack by nitriles. Herein, we report a complementary visible-light-induced three-component Ritter reaction of alkenes, nitriles, and α-bromo nitriles/esters, thereby providing mild and rapid access to various γ-amino nitriles/acids. Mechanistic studies indicated that traceless fluoride relay, transforming KF into imidoyl fluoride intermediate, is critical for the efficient reaction switch from atom transfer radical addition (ATRA) to the Ritter reaction. This approach to amino-alkylation of alkenes is chemoselective and operationally simple.

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Using light irradiation to promote amino-alkylation of alkenes

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Using KF to facilitate three-component Ritter reaction

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Access functionalized amides under mild conditions

Utility of 1-(4-Substituted Aminophenyl)Ethanones in Heterocyclic Synthesis Part(II)

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The improvement of new synthetic routes towards thiophene, oxazole, triazole, pyrimidine, pyridine, quinolone, coumarin, imidazopyrimidine, pyridoimidazole and triazolo[1,5-a] pyridine for their biological and medicinal exploration is an appealing vicinity for researchers. This review focuses on the utility of 1-(4-substituted-aminophenyl) ethanones and their derivatives as critical intermediates for the synthesis of these systems developed within the closing decade.