Copper chloride‐catalyzed aerobic oxidative annulation of N‐furfuryl‐β‐enaminones provides access to polysubstituted pyrroles and indoles. This protocol involves an unprecedented copper chloride‐catalyzed oxidative chlorination of furan and pyrrole rings with oxygen as the terminal oxidant.
A new class of nitro‐functionalized α,β‐unsaturated esters has been prepared by a regio‐ and diastereoselective Michael addition of nitroalkanes to β‐nitroacrylates, performed at room temperature, under carbonate on polymer as promoter, and in the presence of ethyl acetate as eco‐friendly solvent. Moreover, by the modular choice of the reaction conditions the method allows the synthesis of 1,3‐butadiene‐2‐carboxylates. 相似文献
Nanocrystalline magnesium oxide was found to be an effective heterogeneous, solid base catalyst for the one‐pot Wittig reaction to afford α,β‐unsaturated esters and nitriles in excellent yields with high E‐stereoselectivity in the presence of triphenylphosphine under mild conditions. 相似文献
An effective method to synthesize α‐functionalized furan and pyrrole derivatives was developed using 2‐alkoxy‐2,3‐dihydrofurans as modular precursors. This protocol featured a previously unreported tandem nucleophilic substitution/heteroaromatization reaction. Nucleophiles such as indole, α‐oxoketene dithioacetal, trimethoxybenzene, and dimethoxynaphthalene can react readily with 2‐alkoxy‐2,3‐dihydrofurans to afford α‐functionalized five‐membered ring heterocycles in the presence of acid catalysts, such as copper bromide and iron chloride. The mechanism of the reaction was also discussed, in which the first step, nucleophilic substitution, is the key in triggering the succeeding heteroaromatization. This method can also be extended to the synthesis of dihydrothiophenes.
Efficient one‐step syntheses of α,β‐ and β,β‐dihaloenones were achieved by ruthenium(II)‐catalyzed reactions between cyclic or acyclic diazodicarbonyl compounds and oxalyl chloride or oxalyl bromide in moderate to good yields. This methodology offers several significant advantages, which include ease of handling, mild reaction conditions, one‐step reaction, and the use of an effective and non‐toxic catalyst. The synthesized compounds were further transformed into highly functionalized novel molecules bearing aromatic rings on the enone moiety using the Suzuki reaction.
One‐pot, four‐step syntheses of indoles using both solid‐supported heterogeneous and homogeneous palladium catalysts and reagents were carried out. Such a combination of these two‐phase catalysts and reagents causes a dramatic increase in yield, and it is a simple process. The presented methodology is effective for four‐step reactions to provide various functionalized indoles. 相似文献
A new strategy for the synthesis of fluorovinyl acetates and β,β‐difluoro carboxylates using a hypervalent iodine and hydrogen fluoride‐based fluorination reagent is established through a silver‐catalyzed one‐pot reaction involving formation of carbon‐oxygen and carbon‐nitrogen bonds. The generated fluoroalkenes substituted with the carbon‐oxygen and carbon‐nitrogen bond on the β‐position have the potential to be transformed into various products which would be difficult to obtain via direct fluorination.
Carbonate on polymer is a valuable solid supported reagent (SSR) to promote, under eco‐friendly conditions, the preparation of 2H‐1,4‐benzoxazin‐2‐one derivatives starting from β‐nitroacrylates and aminophenols via a domino process. 相似文献
α‐Hydroxylamino phosphonates are synthesised in a one‐pot operation by three‐component coupling reactions of aldehydes, hydroxylamines and diethyl phosphite using 1‐butyl‐3‐methylimidazolium tetrafluoroborate ([bmim]BF4) or 1‐butyl‐3‐methylimidazolium hexafluorophosphate ([bmim]PF6) ionic liquids under mild and neutral conditions. The recovered ionic liquids can be recycled for four to five runs without loss of activity. 相似文献
A novel enzymatic production system of optically pure β‐hydroxy α‐amino acids was developed. Two enzymes were used for the system: an N‐succinyl L ‐amino acid β‐hydroxylase (SadA) belonging to the iron(II)/α‐ketoglutarate‐dependent dioxygenase superfamily and an N‐succinyl L ‐amino acid desuccinylase (LasA). The genes encoding the two enzymes are part of a gene set responsible for the biosynthesis of peptidyl compounds found in the Burkholderia ambifaria AMMD genome. SadA stereoselectively hydroxylated several N‐succinyl aliphatic L ‐amino acids and produced N‐succinyl β‐hydroxy L ‐amino acids, such as N‐succinyl‐L ‐β‐hydroxyvaline, N‐succinyl‐L ‐threonine, (2S,3R)‐N‐succinyl‐L ‐β‐hydroxyisoleucine, and N‐succinyl‐L ‐threo‐β‐hydroxyleucine. LasA catalyzed the desuccinylation of various N‐succinyl‐L ‐amino acids. Surprisingly, LasA is the first amide bond‐forming enzyme belonging to the amidohydrolase superfamily, and has succinylation activity towards the amino group of L ‐leucine. By combining SadA and LasA in a preparative scale production using N‐succinyl‐L ‐leucine as substrate, 2.3 mmol of L ‐threo‐β‐hydroxyleucine were successfully produced with 93% conversion and over 99% of diastereomeric excess. Consequently, the new production system described in this study has advantages in optical purity and reaction efficiency for application in the mass production of several β‐hydroxy α‐amino acids.
The first enantioselective Friedel–Crafts alkylation of indoles and pyrroles with 3‐hydroxy‐3‐indolyloxindoles to access two novel types of 3,3‐diaryloxindoles catalyzed by chiral imidodiphosphoric acids has been reported. A range of quaternary carbon centered 3,3‐diaryloxindoles were synthesized in high yield (up to >99%) with excellent enantioselectivity (up to 98% ee) at low catalyst loadings (as low as 0.5 mol%). The Friedel–Crafts reaction between indoles and 3‐hydroxy‐3‐indolyloxindoles is amenable to gram scale syntheses.
The first catalytic synthesis of β,γ‐alkynyl α‐amino acid derivatives was achieved by direct addition of terminal alkynes to α‐imino esters in the presence of an Ag(I) salt under mild reaction conditions. 相似文献
Based on the combined use of dimethylformamide (DMF) modulation and neighboring group participation, three iterative one‐pot α‐glycosylation methods, i.e., one‐pot (α,α)‐, one‐pot (β,α)‐, and one‐pot (α,β)‐glycosylations, were developed. These methods are applicable to a range of thioglycosyl donors, confer stereocontrol in α‐/β‐glycosidic bond formation, and thus provide for rapid access to oligosaccharides with various permutations of anomeric configurations. The utility of these one‐pot glycosylation methods is demonstrated in the synthesis of eight non‐natural and natural oligosaccharide targets, including the core 1 serine conjugate, core 8 serine conjugate, the D ‐Gal‐α(1→3)‐D ‐Glc‐α(1→3)‐L ‐Rha trisaccharide unit of the cell wall component in Streptococcus pneumoniae, and the D ‐Glc‐α(1→2)‐D ‐Glc‐α(1→3)‐D ‐Glc trisaccharide terminus of the N‐linked glycan precursor. Confirmation of the anomeric configurations of these oligosaccharides is evidenced by 1H, 13C, 13C‐non‐proton decoupling, and heteronuclear correlation 2D NMR experiments. Global deprotection of selected oligosaccharide targets is illustrated. 相似文献
A new [3+2] cycloaddition strategy for the direct synthesis of highly substituted pyrroles from the readily available α‐acylketene dithioacetals (or related substrates) and commercially available propargylamines under mild metal‐free conditions has been developed. In this reaction, the acyl group plays a critical role in driving the conjugate addition of propargylamine and further cyclization to give pyrroles. Furthermore, the wide scope was confirmed by the preparation of 1,2,3,4‐tetrasubstituted pyrroles (60–70% yields) via a formal 1,2‐acyl migrating [3+2] cycloaddition pathway with N‐methylprop‐2‐yn‐1‐amine as the secondary amine component. 相似文献
Several chiral BINOL‐derived bisoxazoline (BOX)/copper(II) complexes were synthesized and evaluated as catalysts for the Friedel–Crafts reaction of indoles with isatin‐derived β,γ‐unsaturated α‐keto esters. The resulting bis‐indole products bearing a quaternary stereocenter were obtained in excellent yields and enantioselectivities. Additionally, the desired products were practically transformed to α‐amino esters, α‐hydroxy esters and α‐keto amides. It is noteworthy that this catalytic procedure was conducted with a catalyst loading of 0.5 mol% without any discernible decrease in the reactivity or enantioselectivity.
We have developed a new strategy for palladium‐catalyzed arylation reactions with triazolopyridines, wherein two different chemical transformations (C‐3 vs. C‐7) are observed by differentiating the substrates using different bases. The reactive palladium carbenoids were directly generated from triazolopyridines and underwent denitrogenative arylations with aryl bromides. Intriguingly, when potassium carbonate was replaced with potassium tert‐butoxide, direct C H arylation occurred at the most acidic position (C‐7). Moreover, two different catalytic arylation events were successfully performed in a one‐pot sequence, providing a convenient access to 6‐aryl‐2‐α‐styrylpyridines.