10.1021/jo900752z
The research focuses on developing an efficient and environmentally friendly method for the N-arylation and benzylation of benzazoles, such as 1H-benzimidazole, 1H-indole, and 1H-benzotriazole, using aryl and benzyl halides. The purpose is to overcome limitations associated with traditional arylation reagents that typically require ligands, bases, and solvents, which can be costly and less efficient. By employing tetrabutylammonium fluoride (TBAF) alongside copper(II) bromide (CuBr2) as a catalyst under solvent-free conditions, the researchers achieved moderate to good yields of N-arylazoles without the need for additional ligands or bases. TBAF appears to play dual roles as both a ligand and a base in this process.
10.1016/j.tet.2015.05.001
The study investigates the enantioselective synthesis of NeC axially chiral indoles using a chiral palladium-catalyzed 5-endo-hydroaminocyclization process. The key chemicals involved include various 2-(tert-butyl)N-(2-ethynylphenyl)anilines as substrates, which undergo the cyclization reaction to form the desired NeC axially chiral N(2-tert-butylphenyl)indole derivatives. The (R)-SEGPHOS-PdCl2 complex serves as the crucial chiral catalyst, enabling the enantioselective transformation. The enantioselectivity of the reaction is significantly influenced by the bulkiness of ortho-substituents on the phenyl group and the electron density on the arylethynyl group of the substrates. The study explores the optimization of reaction conditions, the effects of different substituents on the enantioselectivity and reaction rate, and proposes a mechanism involving the formation of a Pd-aniline complex, followed by conversion to an alkyne-Pd complex and subsequent 5-endo-cyclization to form the indole intermediate. The findings provide valuable insights into the catalytic enantioselective synthesis of non-amide type NeC axially chiral compounds.
10.1016/S0040-4039(01)90354-5
The study presents an efficient methodology for the synthesis of indole derivatives in a single operation using organodilithium reagents and vicinal dication equivalents. Key chemicals involved include 2-bromoaniline derivatives, which are used to prepare organodimetallic reagents through bromine-lithium exchange, a process that facilitates efficient, site-specific lithiation. For instance, 2'-bromo-2,2-dimethylpropionanilide reacts with methyllithium and t-butyllithium to form the organodilithium derivative. This derivative is then reacted with biselectrophiles such as 2-chlorocyclohexanone to produce indole precursors. The study also explores the effects of variations in nitrogen protecting groups and reaction temperatures. The methodology allows for the formation of either N-protected or unprotected indoles, with dehydration induced by trifluoroacetic acid yielding N-protected products like 3,4-tetrahydrocarbazole. The study further demonstrates the versatility of the method by using different biselectrophiles, such as the enolate of cyclohexenone epoxide and enediones, to produce various indole derivatives. The results highlight the regiocontrol and synthetic efficiency of this approach, with high yields and the ability to directly convert commercially available 2-bromoaniline to tetrahydrocarbazole in one operation.
10.3762/BJOC.16.144
The research presents a convergent strategy for synthesizing nitrogen-containing heterocycles, specifically indole, indolone, and cinnoline derivatives, from common 1,4-diketone and primary amine substrates. The authors demonstrate that by varying the substrates, substituents, or heating mode, they can selectively produce these derivatives in moderate to excellent yields. The study involves the preparation of variously substituted 1,4-diketones through Nef and Wittig reactions. The synthesis of indole and indolone derivatives is explored under different conditions, with the reaction mechanism involving imine formation and subsequent 1,2- or 1,4-addition processes. The synthesis of cinnoline derivatives is optimized using hydrazine monohydrate and acetic acid in ethanol under reflux conditions. The developed protocols are mild, metal-free, and functional-group tolerant, making them suitable for medicinal chemistry applications.
10.1002/anie.201306511
The research focuses on the development of a traceless directing group strategy for C-H borylation reactions of nitrogen heterocycles and anilines. The main content revolves around the use of the (pinacolato)boron (Bpin) group as a traceless directing group, which can be readily installed and removed without additional steps, offering an alternative to traditional methods that require installation and removal of directing groups. The experiments involved the borylation of various substrates, including pyrroles, indoles, azaindoles, pyrazoles, and anilines, using the Bpin group. Reactants such as HBpin and iridium catalysts were used, along with tertiary amines to facilitate N-borylation. The analyses included monitoring the reactions by 1H and 11B NMR spectroscopy, and evaluating the yields and selectivity of the borylated products. The study demonstrated that the Bpin-directed approach is operationally simpler and generally higher yielding than the Boc-directed counterparts, and it expands the scope of C-H borylation by enabling functionalization at different positions on the substrates.
10.1021/ja4132505
The study presents a novel high-performance asymmetric catalyst based on metal coordination, specifically utilizing metal centrochirality as the sole element of chirality. The catalyst is an octahedral iridium(III) complex with substitutionally labile yet configurationally stable chirality, which effectively catalyzes the enantioselective Friedel-Crafts addition of indoles to α,β-unsaturated 2-acyl imidazoles. The catalyst, which bears only achiral ligands, demonstrates high yields (75%?99%) and high enantioselectivities (90?98% ee) at low catalyst loadings (0.25?2 mol %). The key chemicals used in the study include iridium(III) complexes (Λ-1 and Δ-1), α,β-unsaturated 2-acyl imidazoles (as substrates), and indoles (as reactants). The purpose of these chemicals is to demonstrate the effectiveness of the chiral-at-metal catalyst in achieving high enantioselectivity and yield in the Friedel-Crafts alkylation reaction, which is a significant advancement in asymmetric catalysis.
10.1021/ol301366p
The research focuses on the development of a metal-free, sp3 C-H bond dual-(het)arylation protocol for the synthesis of 2,2-bisindolyl-1-arylethanones. The purpose of this study was to create a more efficient and environmentally friendly method for synthesizing these compounds, which are of interest in organic chemistry due to their potential applications in pharmaceuticals and materials science. The researchers successfully assembled three distinct reactions—iodination, Kornblum oxidation, and Friedel-Crafts alkylation—into a single reactor process, avoiding the need for metal catalysts, bases, or ligands. The chemicals used in this process include aryl methyl ketones, indoles, molecular iodine (I2), and various other reagents such as CuO, Br?nsted acids, and Lewis acids. The conclusions of the study highlight the successful synthesis of the target compounds with good yields, demonstrating the utility of this novel, metal-free approach in organic chemistry.
10.1021/acs.joc.1c00376
The research focuses on the development of an efficient method for the mono- and dimethylation of ketones, indoles, and arylacetonitriles using a rhenium(I) complex as a catalyst. The purpose of this study is to optimize the reaction conditions for methylation processes, which are significant in organic synthesis for producing various methylated products that serve as intermediates or final compounds in pharmaceuticals, agrochemicals, and materials science.
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