The dehydrogenation adjacent to an electron-withdrawing group provides an efficient access to α,β-unsaturated compounds that serving as versatile synthons in organic chemistry. However, the α,β-desaturation of aliphatic imines has hitherto proven to be challenging due to easy hydrolysis and preferential dimerization. Herein, by employing a pre-fluorination and palladium-catalyzed dehydrogenation reaction sequence, the abundant simple aliphatic amides are amendable to the rapid construction of complex molecular architectures to produce α,β-unsaturated imines.
View Article and Find Full Text PDFVisible-light-induced three-component 1,2-alkylpyridylation of alkenes with unactivated alkyl iodides and aryl cyanides is reported via a photocatalytic halogen-atom transfer (XAT) strategy. This metal-free protocol utilizes readily available tertiary alkylamine as the terminal reductant to smoothly convert alkyl iodides into the corresponding carbon radical species. The reaction features a broad substrate scope, excellent functional group tolerance, high efficiency, and mild reaction conditions.
View Article and Find Full Text PDFWe present herein a copper-catalyzed three-component aminofluorination of unactivated alkenes with N-bromodialkylamines and readily available nucleophilic fluoride under the assistance of a bidentate auxiliary. This protocol exhibits excellent functional group tolerance toward a wide range of unactivated alkenes and N-bromodialkylamines to furnish the corresponding β-fluoroalkylamines in a highly regio- and diastereoselective manner. The appropriate choice of nucleophilic fluoro source is essential to make this reaction a reality.
View Article and Find Full Text PDFThe control of regioselectivity in Heck-type reaction of unactivated alkenes represents a longstanding challenge due to several detachable hydrogens in β-H elimination step, which generally afford either one specific regioisomer or a mixture. Herein, a copper-catalyzed intermolecular Heck-type reaction of unactivated alkenes and N-fluoro-sulfonamides with divergent regioselectivities is reported. The complete switch of regioselectivity mainly depends on the choice of different additives.
View Article and Find Full Text PDFOrganic carbamates represent a kind of privileged structures in both organic chemistry and industry. Despite the fact that the synthesis of alcohol-based carbamates has been well studied, an efficient access to hydroxamic acid-based carbamates is less explored due to the nucleophilicity of both O and N atoms in hydroxamic acids. Herein, we report a copper-catalyzed oxidative coupling of quinazoline-3-oxides and formamides for the synthesis of -quinazolinic carbamates.
View Article and Find Full Text PDFRetigeranic acid A is a uniquely structured pentacyclic sesterterpene bearing eight stereogenic centers. We report a concise route to the core structure of (-)-retigeranic acid A. The stereochemistry of its six chiral centers and three quaternary carbon centers was well-controlled.
View Article and Find Full Text PDFThe catalytic intermolecular diamination of unactivated alkenes with electron-rich amino sources is a challenge. Herein, by employing a directing-group strategy, a copper-catalyzed diamination of unactivated alkenes was realized. Symmetrical diamines were efficiently produced in a highly diastereoselective manner with readily available dialkylamines as amino sources, while a one-pot and two-step operation was necessary to produce the unsymmetrical diamines.
View Article and Find Full Text PDFA new type of coupling between unactivated olefins and nonstabilized alkyl radicals was achieved, which enabled the first intermolecular Heck-type reaction of cycloketone oxime esters and unactivated alkenes. This directing-group-based strategy was compatible with various unactivated alkenes and cyclobutanone-, cyclopentanone-, and cyclohexanone-derived oxime esters. Density functional theory calculations showed that both excellent regioselectivities and good diastereoselectivities could be ascribed to the 2-butanol-assisted concerted H-OBz elimination of the conformationally strained metallacyclic transition state.
View Article and Find Full Text PDFA diverse collection of copper-catalyzed intermolecular aminative difunctionalizations of unactivated alkenes with -halodialkylamines as the terminal dialkylamino source is reported. A bidentate auxiliary tethered on the alkene substrates is crucial, which can promote the migratory insertion of nonactivated alkenes into the aminyl radical-metal complex and stabilize the resultant high-valent copper intermediate to allow for further transformations. By employing this strategy, the intermolecular aminohalogenation reactions and a three-component aminoazidation reaction of unactivated alkenes with dialkylamino source were successively achieved in a remarkable regio- and stereoselective manner.
View Article and Find Full Text PDFA novel reductive cross-coupling of aryl vinyl halides and unactivated tertiary alkyl bromides has been realized via photoredox/nickel dual catalysis to produce vinyl arene derivatives bearing all-carbon quaternary centers with excellent E-selectivity. A stoichiometric metal reductant could be avoided by employing commercially available N,N,N',N'-tetramethylethylenediamine (TMEDA) as the terminal reductant.
View Article and Find Full Text PDFA novel copper-catalyzed C(sp)-N coupling of cycloketone oxime esters with nitrogen nucleophiles has been realized. All of the N-aryl/alkylanilines, anilines and benzophenone imine could be employed in this protocol to produce a variety of 1°, 2° and 3° alkyl amines in one or two steps. These resultant cyano-containing alkyl amines were proven to be versatile synthetic building blocks in a variety of chemical transformations.
View Article and Find Full Text PDFA new type of intermolecular alkylative olefination of unactivated olefins and alkyl halides has been realized for the first time. This copper-promoted Heck-type reaction employs a directing-group strategy to efficiently produce the coupled alkyl olefin products with excellent regio- and stereoselectivity. A broad substrate scope including 1°, 2°, and 3° alkyl bromides and various nonactivated alkenes could be well tolerated.
View Article and Find Full Text PDFAn efficient palladium-catalyzed carbonylation reaction of readily available quaternary ammonium salts with CO is reported for the first time to afford arylacetamides and arylacetic acid esters via benzylic C-N bond cleavage. This protocol features mild reaction conditions under atmospheric pressure of CO, a redox-neutral process without an additional oxidant, and a broad substrate scope for various kinds of amines, alcohols and phenols.
View Article and Find Full Text PDFA multifunctionalization of unactivated cyclic ketones via synergistic catalysis of copper and diarylamine for the direct synthesis of cyclic α-enaminone is reported for the first time. This reaction goes through oxidative α-amination, followed by a desaturation, and features mild reaction conditions, a broad substrate scope, and great functional group tolerance.
View Article and Find Full Text PDFObjective: Primary myelofibrosis (PMF) is one of the Philadelphia negative myeloproliferative neoplasms (MPN). The main clinical features are obvious physical symptoms and symptomatic splenomegaly. It may be converse to leukemia and has a shortened life expectancy.
View Article and Find Full Text PDFVinyl azides are highly versatile synthons that provide access to numerous N-heterocycles and other functional groups. α-Substituted vinyl azides (azido vinylidenes) are a special class that display unique reactivity, able to react not only as azides, but also as radical acceptors, enamine-type nucleophiles, and even electrophiles, thus delivering a wide range of nitrogen-containing compounds and their derivatives. An impressive variety of intermediates - such as iminodiazonium ions, nitrilium ions, iminyl radicals, and metal enaminyl radicals - can be generated from vinyl azides and exploited in cycloadditions, C-H functionalizations, hydrolysis processes, and cascade reactions under transition metal/photoredox catalysis.
View Article and Find Full Text PDFA highly diastereoselective rhodium(II)-catalyzed transannulation of aldehyde-tethered N-sulfonyl triazoles with electron-rich aromatic nucleophiles is reported for the first time to afford functionalized 6-substituted piperidin-3-ones. The reaction has a broad substrate scope including both aliphatic and aromatic N-sulfonyl-1,2,3-triazoles together with various aromatic nucleophiles. The addition of a catalytic amount of Lewis acid has proven to be crucial for the yield improvement.
View Article and Find Full Text PDFAn unexpected silver-catalyzed cascade reaction of β-enaminones and isocyanoacetates affording functionalized pyrrole derivatives is reported. In this reaction, tautomeric equilibria of β-enaminones are utilized to generate imine partners in situ. A hypothesized sequential Mannich addition/cyclization of imine tautomers and isocyanoacetates followed by an unprecedented ring-opening of the resultant 2-imidazolines and dehydration-condensation deliver the final 1,2,4,5-tetrasubstituted pyrrole products.
View Article and Find Full Text PDFA highly effective and straightforward method to construct a wide range of functionalized 2,3-disubstituted indoles has been developed. The method involves the tandem reaction of rhodium(II)-catalyzed denitrogenative annulation of triazole-based benzyl anilines and oxygen-mediated oxidative aromatization. The developed method can also be used to synthesize 2,3-disubstituted benzofurans by replacing the benzyl anilines with benzyl phenols.
View Article and Find Full Text PDFAromatic hydrocarbons are some of the most elementary feedstock chemicals, produced annually on a million metric ton scale, and are used in the production of polymers, paints, agrochemicals and pharmaceuticals. Dearomatization reactions convert simple, readily available arenes into more complex molecules with broader potential utility, however, despite substantial progress and achievements in this field, there are relatively few methods for the dearomatization of simple arenes that also selectively introduce functionality. Here we describe a new dearomatization process that involves visible-light activation of small heteroatom-containing organic molecules-arenophiles-that results in their para-cycloaddition with a variety of aromatic compounds.
View Article and Find Full Text PDFThe development of an efficient diastereoselective synthesis of the oxabicyclo[3.2.1]octane ring system bearing two oxygenated quaternary chiral centres represents a significant challenge.
View Article and Find Full Text PDFTwo novel rhodium(II)-catalyzed tandem reactions were developed for the synthesis of dihydroisobenzofuran and indanone derivatives from 2-triazole-benzaldehydes and 2-triazole-alkylaryl ketones. Dihydroisobenzofuran derivatives were obtained in good yields with high regioselectivities when alcohols were used as nuclophiles in these reactions, whereas the replacement of the alcohol with water resulted in the diastereoselective formation of highly functionalized indanone derivatives.
View Article and Find Full Text PDFA 4-substituted-1-tosyl-1,2,3-triazole-based stereoselective synthesis of structurally diverse oxaspirocycles is reported. The synthesis involves Rh-catalyzed loss of nitrogen from 4-substituted-1-tosyl-1,2,3-triazoles, Grignard reaction, and a ring-closing metathesis reaction as key steps. By employing readily available and stable 4-substituted-1-tosyl-1,2,3-triazoles as surrogates of diazo compounds and nitrogen sources, two types of oxaspirocycles were obtained.
View Article and Find Full Text PDF