Novel α,α-Difluorohomophthalimides via Copper-Catalyzed Tandom Cross-Coupling−Cyclization of 2-Halobenzamides with α,α-Difluoro Reformatskii Reagent

Difluoroalkylative carbonylation of alkenes to access carbonyl difluoro-containing heterocycles: convenient synthesis of gemigliptin

Fluorinated heterocycles play a vital role in pharmaceutical and agrochemical industries. Hence, rapid and efficient construction of fluorinated heterocycles remains highly demanded. Herein, a difluoroalkylative carbonylative cyclization of unactivated alkenes and ethylene gas enabled by palladium catalysis has been developed for the first time toward the synthesis of α-carbonyl difluoro-modified glutarimides. This procedure can also be applied to the synthesis of GeMigliptin which is a medicine approved for the treatment of type 2 diabetes mellitus.

Recent developments in the synthesis of the isoquinoline-1,3(2H,4H)-dione by radical cascade reaction

In recent years, isoquinoline-1,3(2H,4H)-dione compounds have attracted extensive attention from synthetic chemists, with the aim of finding simple, mild, green and efficient synthetic methods. In this review, we summarize the diverse range of synthetic methods employing acryloyl benzamides as key substrates to furnish isoquinoline-1,3-diones using different radical precursors, such as those containing carbon, sulphur, phosphorus, nitrogen, silicon and bromine. This will stimulate the interest of readers to engage in research in this field.

Modular Difunctionalization of Unactivated Alkenes through Bio-Inspired Radical Ligand Transfer Catalysis

Development of visible light-mediated atom transfer radical addition of haloalkanes onto unsaturated hydrocarbons has seen rapid growth in recent years. However, due to its radical chain propagation mechanism, diverse functionality other than the pre-existing (pseudo-)halide on the alkyl halide source cannot be incorporated into target molecules in a one-step, economic fashion. Inspired by the prominent reactivities shown by cytochrome P450 hydroxylase and non-heme iron-dependent oxygenases, we herein report the first modular, dual catalytic difunctionalization of unactivated alkenes via manganese-catalyzed radical ligand transfer (RLT). This RLT elementary step involves a coordinated nucleophile rebounding to a carbon-centered radical to form a new C-X bond in analogy to the radical rebound step in metalloenzymes. The protocol leverages the synergetic cooperation of both a photocatalyst and earth-abundant manganese complex to deliver two radical species in succession to minimally functionalized alkenes, enabling modular diversification of the radical intermediate by a high-valent manganese species capable of delivering various external nucleophiles. A broad scope (97 examples, including drugs/natural product motifs), mild conditions, and excellent chemoselectivity were shown for a variety of substrates and fluoroalkyl fragments. Mechanistic and kinetics studies provide insights into the radical nature of the dual catalytic transformation and support radical ligand transfer (RLT) as a new strategy to deliver diverse functionality selectively to carbon-centered radicals.

Base-Promoted Annulative Difluoromethylenation of Enaminones with BrCF2CO2Et toward 2,2-Difluorinated 2,3-Dihydrofurans

A practical method for the synthesis of 2,2-difluorinated 2,3-dihydrofurans has been established via the [4 + 1] annulation of enaminones and BrCF₂CO₂Et with Na₂CO₃ promotion. This new protocol does not employ any transition metal reagent and enables the annulative difluoromethylation by the partial cleavage of the C═C double bond. In addition, the further treatment with hydrochloric acid in one pot leads to β-keto enoic acids (4-oxo-2-butenoic acids) via a formal enaminone C-N carboxylation.

Visible-light-promoted acyl radical cascade reaction for accessing acylated isoquinoline-1,3(2H,4H)-dione derivatives

A visible-light-promoted radical acylation/cyclization cascade reaction of N-methacryloylbenzamides with α-keto acids was developed to construct acylated isoquinoline-dione derivatives.

Photoredox-Catalyzed Cross-Coupling of Enamides for the Assembly of β-Difluoroimine Synthons

A photoredox-catalyzed formal C_sp3-C_sp3 cross-coupling reaction of enamides with bromodifluoro compounds is established. The resulting gem-difluoromethylenated γ-imines indicated high stability, excellent E/Z control, and broad functional group tolerance. These synthetic intermediates can efficiently transfer to difluoromethylenated γ-amino acids or δ-amino alcohols. Mechanistic analysis indicates that a radical/SET mechanism proceeding via a difluoroalkyl radical may be involved in the catalytic cycle.

Visible-light induced di- and trifluoromethylation of N-benzamides with fluorinated sulfones for the synthesis of CF2H/CF3-containing isoquinolinediones

A photocatalytic radical di- or trifluoromethylation/cyclization of methacryloyl benzamides with fluorinated sulfones provided an efficient route to CF₂H/CF₃-containing isoquinoline-1,3(2H,4H)-diones.

Oxidative decarbonylative coupling of aliphatic aldehydes with methacryloyl benzamides to generate isoquinoline-1,3(2H,4H)-diones

Alkyl-substituted isoquinoline-1,3(2H,4H)-diones were prepared by coupling of N-alkyl-N-methacryloylbenzamides and aliphatic aldehydes through subsequent decarbonylation, radical addition and cyclization processes.

Visible-Light Photoredox-Catalyzed C-H Difluoroalkylation of Hydrazones through an Aminyl Radical/Polar Mechanism

An unprecedented visible-light-induced direct C-H bond difluoroalkylation of aldehyde-derived hydrazones was developed. This reaction represents a new way to synthesize substituted hydrazones. The salient features of this reaction include difluorinated hydrazone synthesis rather than classical amine synthesis, extremely mild reaction conditions, high efficiency, wide substrate scope, ease in further transformations of the products, and one-pot syntheses. Mechanistic analyses and theoretical calculations indicate that this reaction is enabled by a novel aminyl radical/polar crossover mechanism, with the aminyl radical being oxidized into the corresponding aminyl cation through a single electron transfer (SET) process.

Microwave assisted novel and regioselective functionalization of imidazopyridines with chromene acetals and β-nitrostyrenes

A facile synthesis of novel functionalized imidazopyridines has been accomplished through the condensation of imidazopyridines with chromene hemiacetals or β-nitro styrenes with high regioselectivity and excellent yields in the presence of a catalytic amount of PTSA or InCl₃.

Synthesis of isoquinoline-1,3(2H,4H)-dione derivatives via cascade reactions of N-alkyl-N-methacryloyl benzamide with aryl aldehydes

A cascade reaction between N-alkyl-N-methacryloylbenzamide and aryl aldehydes was developed to generate isoquinoline-1,3(2H,4H)-dione derivatives.

O2-sulfonylethyl protected isopropylamine diazen-1-ium-1,2-diolates as nitroxyl (HNO) donors: synthesis, β-elimination fragmentation, HNO release, positive inotropic properties, and blood pressure lowering studies

New types of nonexplosive O(2)-sulfonylethyl protected (-CH(2)CH(2)SO(2)R; R = OMe, NHOMe, NHOBn, Me) derivatives of isopropylamine diazen-1-ium-1,2-diolate (IPA/NO) (2-5) were developed that are designed to act as novel HNO donors. These compounds, with suitable half-lives (6.6-17.1 h) at pH 7.4, undergo a base-induced β-elimination reaction that releases a methyl vinyl sulfone product and the parent IPA/NO anion which subsequently preferentially releases HNO (46-61% range). Importantly, the O(2)-methylsulfonylethyl compound 5 exhibited a significant in vitro inotropic effect up to 283% of the baseline value and increased the rates of contraction and relaxation but did not induce a chronotropic effect. Furthermore, compound 5 (22.5 mg/kg po dose) provided a significant reduction in blood pressure up to 6 h after drug administration. All these data suggest that O(2)-sulfonylethyl protected derivatives of IPA/NO, which are efficient HNO donors, could have potential applications to treat cardiovascular disease(s) such as congestive heart failure.

Synthesis of fluorinated δ-lactams via cycloisomerization of gem-difluoropropargyl amides

gem-Difluoro-1,7-enyne amides are suitable building blocks for the synthesis of difluorodihydropyridinones via a ring-closing metathesis reaction, and of 4,4-difluoro-3-oxoisoquinolines through a ring-closing metathesis–enyne metathesis tandem reaction. These products, in turn, undergo a Diels–Alder reaction to yield heterotricyclic systems in moderate to good yields.

Copper-catalyzed tandem process: an efficient approach to 2-substituted-1,4-benzodioxanes

An efficient method for the preparation of various 2-substituted-1,4-benzodioxanes by CuBr-catalyzed tandem reactions of 2-((o-iodophenoxy)methyl)oxiranes with phenols has been developed. The reaction involves the ring-opening process of 2-((2-iodophenoxy)methyl)oxirane followed by an intramolecular C-O cross coupling cyclization.