CuI-catalyzed Synthesis of Aryl Thiocyanates from Aryl Iodides

Aryl thiocyanates are important compounds not only for their interesting biological properties, but also because of their use as a versatile starting material for many sulfur- containing aromatic compounds, including sulfonyl cyanides, sulfonic acids, sul…     

Visible-Light-Induced Palladium-Catalyzed Generation of Aryl Radicals from Aryl Triflates

A mild visible-light-induced Pd-catalyzed intramolecular C−H arylation of amides is reported. The method operates by cleavage of a C(sp²)−O bond, leading to hybrid aryl Pd-radical intermediates. The following 1,5-hydrogen atom translocation, intramolecular cyclization, and rearomatization steps lead to valuable oxindole and isoindoline-1-one motifs. Notably, this method provides access to products with readily enolizable functional groups that are incompatible with traditional Pd-catalyzed conditions.     

Photohomolysis and Photoheterolysis in Aryl Sulfonates and Aryl Phosphates

The photochemical behaviour of selected aryl sulfonates and phosphates (ArOX) in polar and nonpolar media has been investigated by laser flash photolysis (LFP) experiments. Two main pathways have been identified, namely the photohomolysis of the ArO−X bond or the photoheterolysis of the Ar−OX bond depending on the nature of the leaving group (OX) and on the nature of the substituents on the aromatic ring. In nonpolar solvents the esters are quite photostable due to an efficient triplet deactivation. In polar solvents, the homolytic fragmentation of the ArO−S bond from the exited singlets was found in aryl sulfonates bearing moderately electron-donating groups as well as electron-withdrawing groups. In electron-rich aryl phosphates and sulfonates photoheterolysis of the Ar−OP/Ar−OS bond took place as the exclusive pathway.     

芳甲酸氰基芳甲酯的合成

芳甲酸氰基芳甲酯是重要的有机合成中间体,其现有合成方法采用剧毒氰化物为氰源来合成。 本研究以K₄[Fe(CN)₆]为绿色氰化试剂,芳酰氯为原料,采用一锅两步反应合成芳甲酸氰基芳甲酯。 通过改变第二步反应温度、反应时间、硼氢化钠和催化剂的用量获得最佳反应条件,以61.7%~80.3%的产率合成了10种芳甲酸氰基芳甲酯(2a~2j),产物结构通过傅里叶变换红外光谱仪(FTIR)、核磁共振波谱仪(NMR)分析确认。 根据实验结果,提出了可能的反应机理。 该法避免了对剧毒氰化剂的使用,具有产率高、操作简单、后处理方便等优点。     

Palladacycle-Catalyzed Carbonylation of Aryl Iodides or Bromides with Aryl Formates

An efficient palladacycle-catalyzed aromatic carbonylation reaction of aryl formates with aryl iodides or bromides has been developed. Commercially available and easily prepared aryl formates were employed as carbonyl sources without the use of external carbon monoxide. The present catalytic system shows broad functional group tolerance and affords aryl benzoate derivatives in good to excellent yields.     

Aryl aminoalkyl sulfones

Two methods are proposed for the preparation of aryl aminoalkyl sulfones substituted in the aromatic ring: a method based on the oxidation of aryl aminoalkyl sulfides by hydrogen peroxide or of their bases in the presence of HClO₄ and a method based on the oxidation of aryl -chloroalkyl sulfides to chlorosulfones by hydrogen peroxide followed by their condensation with amines.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, pp. 2580–2585, November, 1989.     

C-Glycosylated Aryl Tins: Versatile Building Blocks for Aryl C-Glycoside Glycomimetics

ABSTRACT

C-glycosylated aryl tins have been prepared as versatile building blocks of physiologically stable glycomimetics for glycoepitopes that have been recognized to serve biologically important roles in cell biochemistry.     

钨酸钠催化芳香腈高选择性氧化制备芳香酰胺

 The preparation of aryl amides by selective oxidation of aryl nitriles using sodium tungstate as catalyst and sodium percarbonate or sodium carbonate-hydrogen peroxide as the oxidant in a methanol and water solution was studied. Aryl nitriles were converted to aryl amides with very high selectivity of 95%～100% at room temperature. The reactivity of aryl nitriles decreased with increasing their branched chain length. In the oxidation of tolunitriles, the oxidation rate of p-tolunitrile and m-tolunitrile was very fast, but the oxidation rate of o-tolunitrile was very slow. The oxidation rate of p-haloid aryl nitriles and p-nitro aryl nitrile decreased in the order p-nitrobenzonitrile＞p-chlorobenzonitrile＞p-bromobenzonitrile, while the selectivity for aryl amides was maintained at a high level of 98%～100%. The comparison of the two oxidants showed that when sodium carbonate-hydrogen peroxide was used as oxidant, the oxidation rate and selectivity were better than that when percarbonate was used. The sodium tungstate catalyst and carbonate can be reused and the catalytic activity and selectivity did not change if a suitable amount of hydrogen peroxide was supplied. This work provides a convenient method for the preparation of aryl amides from aryl nitriles under very mild reaction conditions.     

LiCl-Accelerated Nickel Catalyzed Cross-Coupling of Aryl Tosylates with the Aryl Grignard Reagents

Russian Journal of General Chemistry - A mild coupling reaction catalyzed by Ni(acac)2-L4 has been studied. The catalyst acts efficiently in the reaction of biaryl coupling between various...     

Dehydration of Aryl Aldoximes

The conversion of aldoximes into nitriles is a well known, straightforward and important organic operation which may be brought about by the action of common dehydrants such as acetic anhydride¹ and mesyl chloride^2. This paper describes a new method of effecting the reaction.     

卤代芳烃的氰基化反应

以亚铁氰化钾为氰基化试剂,以醋酸钯为催化剂制备了芳香族氰基化合物。考察了原料比、时间、反应温度、催化剂的用量等反应条件对反应的影响,确定了较佳的反应条件。在n(K4[Fe(CN)6].3H2O):n(PhBr):n(Pd(OAc)2)=200:1000:1,反应温度130℃,反应1.5h条件下,溴苯转化率达99%,产物氰基苯收率为95%。氰基化试剂亚铁氰化钾与传统的氰基化试剂相比无毒,无需经过复杂的预处理,而且廉价易得。这种氰基化反应催化体系简单,无需添加昂贵的催化剂配体,催化剂的用量少,并且反应的后处理简单,对环境污染小,是一种效益明显的氰化芳烃的制备方法。同时进一步考察了其它卤代芳烃的氰基化反应,活泼的溴代芳烃和碘代芳烃均能得到很好得率:91%～96%。     

Reduction of Aryl Thiocyanates with SmI(2) and Pd-Catalyzed Coupling with Aryl Halides as a Route to Mixed Aryl Sulfides

A series of aryl iodides, with a range of substituents, has been successfully coupled using 10 mol % Pd catalyst with samarium thiolates, derived from the corresponding aryl thiocyanates upon reductive cleavage with SmI(2). Reactions proceed in THF at 65 degrees C in yields ranging from good to excellent and are compatible with both electron-donating and electron-withdrawing substituents, except NO(2). The reactions may also be conducted with aryl bromides although with somewhat lower yields.     

Metallaphotoredox Difluoromethylation of Aryl Bromides

Herein, we report a convenient and broadly applicable strategy for the difluoromethylation of aryl bromides by metallaphotoredox catalysis. Bromodifluoromethane, a simple and commercially available alkyl halide, is harnessed as an effective source of difluoromethyl radical by silyl‐radical‐mediated halogen abstraction. The merger of this fluoroalkyl electrophile activation pathway with a dual nickel/photoredox catalytic platform enables the difluoromethylation of a diverse array of aryl and heteroaryl bromides under mild conditions. The utility of this procedure is showcased in the late‐stage functionalization of several drug analogues.     

Aryl Triflates in On-Surface Chemistry

The reactivity of aryl triflates in on-surface C−C coupling is reported. It is shown that the triflate group in aryl triflates enables regioselective homo coupling with preceding or concomitant hydrodetriflation on Cu(111). Three different symmetrical π-systems with two and three triflate functionalities were used as monomers leading to oligomeric conjugated π-systems. The cascade, comprising different intermediates at different reaction temperatures as observed for one of the molecules, proceeds via initial removal of the trifluoromethyl sulfonyl group to give an aryloxy radical which in turn is deoxygenated to the corresponding aryl radical. Thermodynamically driven regioselective 1,2-hydrogen atom transfer leads to a translocated aryl radical which in turn undergoes coupling. For a sterically more hindered bistriflate, where one ortho position was blocked, dehydrogenative coupling occurred at remote position with good regioselectivity. Starting materials, intermediates as well as products were analyzed by scanning tunneling microscopy. Structures and suggested mechanism were further supported by DFT calculations.     

Aryl vinyl cyclopropane Cope rearrangements

While the divinyl cyclopropane Cope rearrangement is well-known, and has been broadly applied in synthesis, examples of the aryl vinyl cyclopropane Cope rearrangement are less common and generally limited in scope or reaction yield. The aryl vinyl cyclopropane Cope rearrangement gives access to the benzocycloheptene scaffold, which is present in a variety of naturally occurring and medicinally relevant products. Herein we report a method to obtain either of two regioisomeric benzocycloheptene products via an aryl vinyl cyclopropane Cope rearrangement, featuring additive-controlled regioselectivity. Mechanistic studies indicate a dynamic equilibration of cyclopropane stereoisomers, followed by rearrangement of the cis diastereomer.     

Copper-Catalyzed Coupling of Thiourea with Aryl Iodides:The Direct Synthesis of Aryl Thiols

A general, economical and efficient protocol for the direct copper‐catalyzed coupling of thiourea with aryl iodides is developed and it will be potentially applied in large‐scale industry as a preferred process.     

三氟乙烯基芳基醚的合成

三氟乙烯基芳基醚;四氟二溴乙烷;酚;三氟乙烯基芳基醚的合成     

Reduction of Aryl Trifluoromethyl Oximes

Borane-tetrahydrofuran complex reduces trifluoromethyl oximes to trifluoromethyl hydroxylamines in good yields.