Efficient Synthesis of Diaryl Ketones by Nickel‐Catalyzed Negishi Cross‐Coupling of Amides by Carbon–Nitrogen Bond Cleavage at Room Temperature Accelerated by a Solvent Effect

The first Negishi cross‐coupling of amides for the synthesis of versatile diaryl ketones by selective C?N bond activation under exceedingly mild conditions is reported. The cross‐coupling was accomplished with bench‐stable, inexpensive precatalyst [Ni(PPh₃)₂Cl₂] that shows high functional‐group tolerance and enables the synthesis of highly functionalized diaryl ketone motifs. The coupling occurred with excellent chemoselectivity favoring the ketone (cf. biaryl) products. Notably, this process represents the mildest conditions for amide N?C bond activation accomplished to date (room temperature, <10 min). Considering the versatile role of polyfunctional biaryl ketone linchpins in modern organic synthesis, availability, and excellent functional‐group tolerance of organozinc reagents, this strategy provides a new platform for amide N?C bond/organozinc cross‐coupling under mild conditions.     

Total synthesis of PGF2α and 6,15-diketo-PGF1α and formal synthesis of 6-keto-PGF1α via three-component coupling

The asymmetric total synthesis of PGF_2α and 6,15-diketo-PGF_1α and formal synthesis of 6-keto-PGF_1α from a common key intermediate are described. The key intermediate, which has a chiral cyclopentane backbone possessing suitable functional groups with required stereochemistry for both side chains, was prepared from (R)-4-silyloxy-2-cyclopentenone through a three-component coupling reaction. The Wittig reaction, Nozaki-Hiyama-Kishi (NHK) coupling and cross metathesis completed the synthesis of PGF_2α, 6,15-diketo-PGF_1α and 6-keto-PGF_1α.     

Electrocatalytic Urea Synthesis with 63.5 % Faradaic Efficiency and 100 % N-Selectivity via One-step C−N coupling

Electrocatalytic urea synthesis via coupling N₂ and CO₂ provides an effective route to mitigate energy crisis and close carbon footprint. However, the difficulty on breaking N≡N is the main reason that caused low efficiencies for both electrocatalytic NH₃ and urea synthesis, which is the bottleneck restricting their industrial applications. Herein, a new mechanism to overcome the inert of the nitrogen molecule was proposed by elongating N≡N instead of breaking N≡N to realize one-step C−N coupling in the process for urea production. We constructed a Zn−Mn diatomic catalyst with axial chloride coordination, Zn−Mn sites display high tolerance to CO poisoning and the Faradaic efficiency can even be increased to 63.5 %, which is the highest value that has ever been reported. More importantly, negligible N≡N bond breakage effectively avoids the generation of ammonia as intermediates, therefore, the N-selectivity in the co-electrocatalytic system reaches100 % for urea synthesis. The previous cognition that electrocatalysts for urea synthesis must possess ammonia synthesis activity has been broken. Isotope-labelled measurements and Operando synchrotron-radiation Fourier transform infrared spectroscopy validate that activation of N−N triple bond and nitrogen fixation activity arise from the one-step C−N coupling process of CO species with adsorbed N₂ molecules.     

CuI‐Catalyzed coupling reaction of diazophosphonates with ferrocenylacetylenes: an efficient synthesis of ferrocene‐containing allenylphosphonates

An efficient synthesis of ferrocene‐containing allenylphosphonates via CuI‐catalyzed coupling reaction of diazophosphonates with ferrocenylacetylenes in the presence of Et₃N has been reported. This coupling methodology is applicable to a broad scope of substrates, allowing the synthesis of a range of synthetically valuable ferrocene‐containing trisubstituted allene derivatives in moderate to excellent yields.     

Influence of steric effects in solid-phase aza-peptide synthesis

Aza-peptides are peptide analogs with potential applications as drug candidates. However, due to difficulties associated with the synthesis of these compounds, information regarding their bioactivity is very limited. Herein, we identify steric hindrance as one reason for the slowness of the aza-peptide bond formation reaction. The steric effect of the side group of amino acids in their coupling with the semicarbazide moiety in the synthesis of a model peptide, H-AA-AzAla-Phe-NH₂, was studied and quantified using COMU as a coupling reagent. Characterization of the role of this structural factor in aza-peptide bond synthesis is essential for outlining a new and efficient synthesis protocol.     

Indium Tribromide Catalyzed Coupling Reaction of Enol Ethers with Silyl Ketene Imines toward the Synthesis of β,γ‐Unsaturated Nitriles

Herein, a coupling reaction of enol ethers with silyl ketene imines in the presence of catalytic amounts of InBr₃ and Me₃SiBr is described. Kinetic studies have revealed that an indium catalyst and Me₃SiBr accelerated the coupling process and the regeneration of the catalyst, respectively. Various types of enol ethers and silyl ketene imines are applicable. In addition, a formal synthesis of verapamil was achieved by using this novel coupling reaction.     

Progress toward the polymerization of a fourth generation dendritic macromonomer

The g‐scale synthesis of the fourth generation dendronized monomer 3 d and its Suzuki oligomerization are reported. The monomer synthesis uses the fact that the addition of two G‐3 fragments to aryldibromide 3 c which already contains one branching unit is more practical than an alternative approach by which a G‐4 dendron is added to a respective compound. The Suzuki cross‐coupling of 3 d gives oligomeric material 5 , a fraction of which with a molecular weight of M_n = 170 000 is obtained by preparative gel permeation chromatography. This finding shows that the Suzuki cross‐coupling reaction can cope with considerable steric loading of coupling components which opens up new perspectives for its applicability both in organic and polymer chemistry.     

Anionic methods for synthesis of star polymers

Leading position among numerous methods for synthesis of star polymers is occupied, as regards their potential and diversity, by techniques based on the anionic polymerization. The review considers five basic approaches to application of the anionic polymerization mechanisms in relation to an agent used or procedure employed (methods with polyfunctional coupling agents, multifunctional initiators, polymerizing and nonpolymerizing divinyl agents; multistage methods, methods using C₆₀ fullerene). All groups of syntheses are illustrated by examples, and advantages of methods for synthesis of various homo- and heteroarm star structures are demonstrated. Particular attention is given to syntheses with C₆₀ fullerene. The potential of C₆₀ fullerene as a coupling agent for “living” polymer chains and methods for conversion of polymeric derivatives of C₆₀ (hexaadducts) to polyfunctional macroinitiators of anionic polymerization are described and techniques for functionalization of polymeric fullerene derivatives and their coupling into structures with a complex controllable architecture are presented.     

Stereodivergent Synthesis of Arylcyclopropylamines by Sequential CH Borylation and Suzuki–Miyaura Coupling

A step‐economical and stereodivergent synthesis of privileged 2‐arylcyclopropylamines (ACPAs) through a C(sp³)? H borylation and Suzuki–Miyaura coupling sequence has been developed. The iridium‐catalyzed C? H borylation of N‐cyclopropylpivalamide proceeds with cis selectivity. The subsequent B‐cyclopropyl Suzuki–Miyaura coupling catalyzed by [PdCl₂(dppf)]/Ag₂O proceeds with retention of configuration at the carbon center bearing the Bpin group, while epimerization at the nitrogen‐bound carbon atoms of both the starting materials and products is observed under the reaction conditions. This epimerization is, however, suppressed in the presence of O₂. The present new ACPA synthesis results in not only a significant reduction in the steps required for making ACPA derivatives, but also the ability to access either isomer (cis or trans) by simply changing the atmosphere (N₂ or O₂) in the coupling stage.     

Stereodivergent Synthesis of Arylcyclopropylamines by Sequential C?H Borylation and Suzuki–Miyaura Coupling

A step‐economical and stereodivergent synthesis of privileged 2‐arylcyclopropylamines (ACPAs) through a C(sp³) H borylation and Suzuki–Miyaura coupling sequence has been developed. The iridium‐catalyzed C H borylation of N‐cyclopropylpivalamide proceeds with cis selectivity. The subsequent B‐cyclopropyl Suzuki–Miyaura coupling catalyzed by [PdCl₂(dppf)]/Ag₂O proceeds with retention of configuration at the carbon center bearing the Bpin group, while epimerization at the nitrogen‐bound carbon atoms of both the starting materials and products is observed under the reaction conditions. This epimerization is, however, suppressed in the presence of O₂. The present new ACPA synthesis results in not only a significant reduction in the steps required for making ACPA derivatives, but also the ability to access either isomer (cis or trans) by simply changing the atmosphere (N₂ or O₂) in the coupling stage.     

13C13C spin coupling constants in phenanthrene derivatives

The synthesis of six 1-X- (X = OH, OCH₃, OCOCH₃, CH₃, CHO and CN) phenanthrene derivatives with a ¹³C label at C-1 is described. An analysis of the ¹³C¹³C spin coupling constants shows the importance of π-interaction for the coupling constant transmission. Small ¹³C¹³C spin coupling constants over 6 bonds are reported.     

Unsymmetrically Substituted Aliphatic Diacetylenes Containing Amine Functionalities

A one-pot reaction which combines the Cadiot-Chodkiewicz coupling reaction with the Gabriel synthesis of primary amines is evaluated as a means for the synthesis of unsymmetrically disubstituted aminodiacetylenes of the type CH₂-(CH₂)_n-C≡C-C≡C-CH₂-NH₂ (n=2,3,4,5).     

The first construction of a 3,6-bridged ellagitannin skeleton with C4/B glucose core; synthesis of nonamethylcorilagin

The synthesis of nonamethylcorilagin is described. In the synthesis, the intramolecular Ullmann coupling afforded the (R)-hexahydroxydiphenoyl part--a characteristic bridge structure of the target molecule--when the glucopyranose ring was opened in advance. This synthesis demonstrates the first synthetic approach to a 3,6-bridged ellagitannin skeleton whose conformation of the d-glucose core is ¹C₄ or skew boat.     

Kinetic Control over Morphology of Nanoporous Graphene on Surface

On-surface synthesis of high-quality nanoporous graphene (NPG) for application in nanotechnology and nanodevices remains challenging. Rational design of molecular precursors and proper kinetic control over the reaction process are the two key factors to tune the synthesis. Herein, we report a detailed study of the coupling reactions of a planar halogen-substituted nanographene molecular precursor, hexaiodo-peri-hexabenzocoronene (I₆-HBC), on the Au(111) surface in the synthesis of NPG. The influence of three basic kinetic processes – molecular adsorption, migration, and coupling – on the synthesis was investigated. The results show that the HBC molecules deposited at low temperature predominantly desorb from the Au(111) surface during the annealing process, whereas depositing the precursor molecules onto a hot surface (700 K) can lead to the formation of NPG. However, at such a high surface temperature, simultaneous intermolecular dehydrogenative coupling between HBC monomers can hinder the ordered growth of NPG through Ullmann coupling. Moreover, the deposition rate of the precursors greatly influences the growth morphology of the NPG nanostructures.     

First report of a nano‐Cu2O‐catalyzed protocol for homo‐coupling reaction of terminal alkynes in water/ionic liquid medium

A new, efficient and green protocol for the nano‐Cu₂O‐catalyzed homo‐coupling reaction of terminal alkynes has been developed, using water/ionic liquid as an environmentally friendly solvent. Moreover, the system also allows the synthesis of unsymmetric 1,3‐diynes by cross‐coupling of two different terminal alkynes. It is noteworthy that the nano‐Cu₂O‐catalyzed methodology is a good supplement to copper catalyst for the Glaser‐type homo‐coupling reaction. Copyright © 2016 John Wiley & Sons, Ltd.     

Towards the total synthesis of Calyculin C: preparation of the C13-C25 spirocyclic core

A stereoselective synthesis of the C₁₃-C₂₅ of Calyculin C is described. Key steps involve the coupling of a terminal acetylene with a thiol ester and subsequent spirocyclisation using a double intramolecular hetero-Michael addition.     

碳一化工路线制备乙二醇研究进展

乙二醇(EG)是一种重要的化工原料,主要用来生产新型聚酯纤维.近年来由于我国聚酯产业发展迅速,极大的推动了对乙二醇的需求.碳一化工路线以资源丰富、价格便宜的天然气或煤为原料合成乙二醇,有着诱人的工业化前景.综述了以合成气为原料合成乙二醇的研究进展,包括合成气直接合成法、甲醛羰化法、CO偶联法、甲醛氢甲酰化法以及甲醛缩合法等.     

(±)-Palstatin的首次全合成研究

以廉价易得的5-溴香草醛和2,4,6-三羟基苯乙酮为起始原料，首次方便,高效地合成了(±)-Palstatin (1).合成的关键步骤为SeO₂促进的氧化环化和Ag₂O催化的氧化偶联反应.     

Highly Chemoselective Catalytic Coupling of Substituted Oxetanes and Carbon Dioxide

The chemoselective coupling of oxetanes and carbon dioxide to afford functional, heterocyclic organic compounds known as six‐membered cyclic carbonates remains a challenging topic. Here, an effective method for their synthesis relying on the use of Al catalysis is described. The catalytic reactions can be carried out with excellent selectivity for the cyclic carbonate product tolerating various (functional) groups present in the 2‐ and 3‐position(s) of the oxetane ring. The presented methodology is the first general approach towards the formation of six‐membered cyclic carbonates (6MCCs) through oxetane/CO₂ coupling chemistry. Apart from a series of substituted six‐membered cyclic carbonates, also the unprecedented room‐temperature coupling of oxetanes and CO₂ is disclosed giving, depending on the structural features of the substrate, a variety of five‐ and six‐membered heterocyclic products. A mechanistic rationale is presented for their formation and support for the intermediary presence of a carbonic acid derivative is given. The presented functional carbonates may hold great promise as building blocks in organic synthesis and the development of new, biodegradable polymers.     

Biomimetic Formation of Macrocyclic Spermine Alkaloids

Dihydroxyverbacine ( 10 ), a precursor for oxidative phenol coupling, was obtained via (±)‐buchnerine ( 14 ), whose synthesis is described. The oxidizing system hemin (ferriprotoporphyrin IX chloride)/H₂O₂ promoted intramolecular coupling of 10 to give the alkaloids aphelandrine ( 1 ), orantine ( 2 ), and chaenorpine ( 7 ). The alkaloids were identified by on‐line coupled HPLC and atmospheric‐pressure chemical‐ionization (APCI) mass spectrometry.