Selective Ortho Chlorination of Phenols with n,n-Dichloro-t-Butylamine in Various Solvents

Chlorination of phenol with N,N-dichlororo-t-butylamine (DCB) in appropriate solvents affording o- and p-chlorophenols exhibits high ortho/para ratio up to >10. Solvents associate with phenolic OH group and interfere with the hydrogen bonding between phenol and DCB tend to decrease both rate of reaction and ortho/para ratio; e.g., <1.1 in acetonitrile. The reaction shows autocatalysis exerted by a product, t-butylamine, which would accelerate the reaction by abstracting a proton from the benzene site on which C1 of DCB attacks. Anhydrous sodium phenoxide is little chlorinated. These facts imply a transition state in which phenol and DCB is hydrogen-bonded for the ortho chlorination. This type of chlorination is applicable to the ortho chlorination of other phenols.     

Assay of Phenols and Arylamines via Peroxidatic Coupling

Abstract

Assay procedures are described for phenols and arylamines involving oxidative coupling, employing peroxide-peroxidase, to form the highly colored indaniline and indamine dyes, respectively. The phenols and arylamines are assayable in the 10^?6 to 10^?5 molar range. Appropriate conditions for maximum dye formation are described.     

Synthesis of 3-(1-Cyclohexenyl)-2-butanone via Environmentally Friendly Catalysts

Introduction3- ( 1 - Cyclohexenyl) - 2 - butanone( CHB) is oneofthe importantchemicals and has a potential valuein perfume industry.Beak et al.[1] reported thatthe acylation of ethylidenecyclohexane( EDC) withzinc chloride as a catalystgave3- ( 1 - cyclohexenyl) -2 - butanone in a good yield,butthey have notmadea more detailed investigation.The use of such aconventional catalyst as zinc chloride leads to anumber of problems such as corrosion,unclean re-action products and the disposal of pot…     

Cyclisation of benzils

Treatment of several substituted benzils [3,3′- and 4,4′-dimethyl-; 2,2′-, 3,3′- and 4,4′-dichloro-; 3,3′-dibromo-; 4-(N,N-dimethylamino)-] with an excess of chlorosulfonic acid gave the corresponding 3-chloro-2-phenylbenzofuran disulfonyl dichlorides. Disubstitution was confirmed by microanalytical and spectral data for the corresponding bis(N,N-dimethylaminsulfonamides). The positions of electrophilic substitution were not confirmed with 3,3′-dimethyl-, 2,2′- and 3,3′-dichlorobenzils. With 4,4′-dichlorobenzil, a smaller amount of chlorosulfonic acid enabled the isolation of 3,6,4′-trichloro-2-phenylbenzofuran-5-sulfonyl chloride, which was identified by X-ray analysis of the N,N-dimethylsulfonamide. The cyclisation failed with 3,3′-dimethoxy-, and 3,3′- and 4,4′-dinitrobenzils. The results have been interpreted mechanistically.     

Asymmetric Dearomatization of Phenols via Ligand-Enabled Cooperative Gold Catalysis

By employing a chiral bifunctional phosphine ligand, a gold(I)-catalyzed efficient and highly enantioselective dearomatization of phenols is achieved via versatile metal-ligand cooperation. The reaction is proven to be remarkably general in scope, permitting substitutions at all four remaining benzene positions, accommodating electron-withdrawing groups including strongly deactivating nitro, and allowing carbon-based groups of varying steric bulk including tert-butyl at the alkyne terminus. Moreover, besides N-(o-hydroxyphenyl)alkynamides, the corresponding ynoates and ynones are all suitable substrates. Spirocyclohexadienone-pyrrol-2-ones, spirocyclohexadienone-butenolides, and spirocyclohexadenone-cyclopentenones are formed in yields up to 99 % and with ee up to 99 %.     

Facile Preparation of Substituted Allenic Esters via the Ortho Ester Claisen Rearrangement

Five substituted allenic esters were prepared in good yields through the ortho ester Claisen rearrangement of primary and secondary propargyl alcohols.     

大位阻烯烃不对称环氧化合成手性环氧化合物

采用大位阻的有机锂试剂或格氏试剂与卤代烯烃偶联合成了7种大位阻取代烯烃. 以Oxone(KHSO₅)作为氧化剂, 分别在D-果糖衍生酮和(2S,5R)-2-异丙基-5-甲基环己酮为催化剂的催化下, 将合成的7种大位阻取代烯烃转变成了7个大位阻的手性环氧化合物. 其中以D-果糖衍生酮的对映选择性最好, 当双键碳上含有3个取代基时, 对映选择性最高, e.e.值为96.8%~99.5%. (2S, 5R)-2-异丙基-5-甲基环己酮的对映选择性较差, 无论是一取代的烯烃还是三取代的烯烃, 其e.e.值均介于25.6%~34.1%之间.     

Synthesis of Phenols via Fluoride-free Oxidation of Arylsilanes and Arylmethoxysilanes

Rapid, efficient methods have been developed to prepare phenols from the oxidation of arylhydrosilanes. The effects of arene substituents and fluoride promoters on this process show that while electron-deficient arenes can undergo direct oxidation from the hydrosilane, electron-rich aromatics benefit from silane activation via oxidation to the methoxysilane using homogeneous or heterogeneous transition metal catalysis. The combination of these two oxidations into a streamlined flow procedure involving minimal processing of reaction intermediates is also reported.     

Cyclisation reactions of bis-protected guanidines

The cyclisation of N-allyl- and N-homoallylguanidines using DMDO or I₂/K₂CO₂ leading to novel heterocycles is reported.     

Cyclisation of bisphosphonate substituted enynes

A new synthetic route to the bisphosphonate enyne tetraethyl hept-1-yn-6-en-4,4-diylbisphosphonate has been developed and the enyne has been used successfully in a range of transition metal-catalysed cyclisations that give structurally varied products. The motifs generated via such reactions provide new scaffolds for constructing bisphosphonic acids, an important class of therapeutic agents. NMR experiments indicate that the introduction of phosphonate substitutents onto cyclisation substrates provides a promising new approach to studying metal-catalysed cyclisations.     

Synthesis of Pterocarpan-Type Heterocycles via Oxidative Cycloadditions of Phenols and Electron-Rich Arenes

Oxidation of 4-alkoxyphenols or 4-methoxynaphthol with phenyl iodonium(bis)trifluoroacetate (PIFA) in the presence of electron rich 2H-chromenes or dihydronaphthalenes affords pterocarpans or 5-carbapterocarpans via a formal [3 + 2] cycloaddition process. Acid-catalyzed ionization of quinone dimethylmonoacetal in the presence of 7-methoxy-2H-chromene gave similar results, suggesting a phenoxonium ion intermediate in the oxidative process.     

Isothiourea-Catalyzed Atropselective Acylation of Biaryl Phenols via Sequential Desymmetrization/Kinetic Resolution

Axially chiral phenols are attractive targets in organic synthesis. This motif is central to many natural products and widely used as precursors to, or directly, as chiral ligands and catalysts. Despite their utility few simple catalytic methods are available for their synthesis in high enantiopurity. Herein the atropselective acylation of a range of symmetric biaryl diols is investigated using isothiourea catalysis. Studies on a model biaryl diol substrate shows that the high product er observed in the process is a result of two successive enantioselective reactions consisting of an initial enantioselective desymmetrization coupled with a second chiroablative kinetic resolution. Extension of this process to a range of substrates, including a challenging tetraorthosubstituted biaryl diol, led to highly enantioenriched products (14 examples, up to 98:2 er), with either HyperBTM or BTM identified as the optimal catalyst depending upon the substitution pattern within the substrate. Computation has been used to understand the factors that lead to high enantiocontrol in this process, with maintenance of planarity to maximize a 1,5-S⋅⋅⋅O interaction within the key acyl ammonium intermediate identified as the major feature that determines atropselective acylation and thus product enantioselectivity.     

New Reactions of Ortho Esters

Russian Journal of Organic Chemistry - A new reaction of triethyl orthoformate with ethyl butyrate has been revealed. It afforded diethoxymethyl butanoate and its hydrated form,...     

Epoxidation of homoisoflavones

A comparative study of the epoxidation of homoisoflavones (3‐benzyl‐4‐chromones) 1–4 has been performed by various oxidizing agents, víz. Epoxidation with isolated dimethyldioxirane (Method A), with alkaline hydrogen peroxide (Method B), and with sodium hypochlorite (Method C) to obtain the epoxides 4–8 . Compounds 2 and 3 have also been oxidized with a combination of dimethyldioxirane and Jacobsen's Mn(III)salen catalysts (R,R)‐11 and (S,S)‐ 11 to afford 3‐benzoyl‐4‐chromones 9 and 10 . Structures of all new compounds have been elucidated by microanalyses, ir and nmr spectroscopic measurements.     

亚甲基二硝胺的杂环化和Mannich反应产物的合成

由新的合成路线合成了亚甲基二硝胺；研究了亚甲基二硝胺的Ｎ－烷基化反应，分离出一种新的多硝基多氮杂三环氮杂环硝胺。改进了由亚甲基二硝胺合成３，７－二硝基－１，３，５，７－四氮杂［３．３．１］壬烷（ＤＰＴ）的方法。     

Epoxidation of chalcones

Previously undescribed aromatic α-keto oxides have been obtained by the epoxidation of chalcones with alkaline hydrogen peroxide in methanolic solution.