The Chemistry of the Diaryl Ethers.

Ungnade, Herbert E.

doi:10.1021/cr60121a002

Cited by 32 publications

(8 citation statements)

References 152 publications

(312 reference statements)

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“…Known syntheses of 2-aryloxyphenols can be broadly classified into three categories such as metal-catalyzed couplings [8][9][10][11], condensation of phenols [12,13], and oxidative aromatization of 2-aryloxycyclohex-2-en-1-ones using metals like copper [14], palladium [15], and vanadium [16]. All the Scheme 1.…”

Section: IVmentioning

confidence: 99%

Metal-free oxidative aromatization of 2-aryloxycyclohex-2-en-1-ones to 2-aryloxyphenols using DDQ/Amberlyst-15

Jadhav

Samant

2014

Russ J Org Chem

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Efficient metal-free oxidative aromatization of 2-aryloxycyclohex-2-en-1-ones was achieved by a combination of 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ) and Amberlyst-15. The conditions for oxidative aromatization are mild and applicable for a variety of substrates, and Amberlyst-15 can be successfully recovered and recycled. 2-Aryloxyphenols constitute an important structural motif in medicinal chemistry, which shows a wide spectrum of therapeutic applications. For example, 2-phenoxyphenol (I) and Triclosan (II) are antibacterial drugs [1], while 2-aryloxyphenol containing biologically active peptides viz. vancomycin family member isodityrosine (III) [2], K-13, [3] OF-4949-I-IV [4], Bouvardin [5], and RA I-IV [6] exhibit antitumor activity. Besides these important applications, 2-aryloxyphenols are important building blocks for the synthesis of polycyclic furans like IV [7].above methods suffer from such drawbacks as the use of metals, high temperatures, complex reaction systems, poor yields, and limited scope of substrates.Oxidative aromatization of cyclohexenones to phenols is an important transformation in organic synthesis, so metal-free oxidative aromatization is highly desirable. The best choice of reagents for oxidative aromatization of substituted cyclohexenones would be iodine and DDQ (2,3-dichloro-5,6-dicyano-p-benzoquinone). However, oxidative aromatization of substituted cyclohexenones with iodine in methanol afforded directly aryl phenyl ethers instead of 2-aryloxyphenols [17]. DDQ has been investigated as a powerful oxidant by several research groups [18] and was proved to be useful for a wide range of reactions. This prompted us to use DDQ for oxidative aromatization of 2-aryloxycyclohex-2-en-1-ones to 2-aryloxyphenols. DDQ can be activated by Brønsted acids like concd. HCl, concd. H 2 SO 4 , and TsOH, but these acids are corrosive. Replacement of these acids by solid acids is always desirable.Herein we report for the first time the use of a combination of DDQ and a solid acid, Amberlyst-15, for efficient and metal-free oxidative aromatization of 2-aryloxycyclohexenones to 2-aryloxyphenols. Amberlyst-15 has been recovered and recycled successfully. The reaction conditions are mild, and 2-aryloxyphenols are obtained in good yield. 2-Aryloxycyclohex-2-en-1-ones Va-Vj were prepared by ring opening of 2,3-epoxycyclohexanone with phenols using K 2 CO 3 in acetonitrile under reflux.Oxidative aromatization was attempted in the presence of various well known oxidants. Oxidative aro-

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Section: IVmentioning

confidence: 99%

Metal-free oxidative aromatization of 2-aryloxycyclohex-2-en-1-ones to 2-aryloxyphenols using DDQ/Amberlyst-15

Jadhav

Samant

2014

Russ J Org Chem

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“…This compound was cycJized with potassium carbonate in boiling dimethylformamide in the presence of copper; compound fa was obtained and characterized by analyses and spectra. The same substance was obtained in a single step by a reaction of 2-hydroxythiopheno l 5 and 2-bromobenzyl bromide 4 in the ' presence of potassium carbonate in dimethylformamide first at room temperature (reaction of the benzyl bromide with the thioI) and after the add ition of copper as a catalyst by boiling the mixture (Ullmann reaction 6 ). then to separation of a solid precipitate; the following treatment with an excess of solid carbon dioxide results in I1H-dibenz[b,f)-1,4-oxathiepin-ll-carboxylic acid which was characterized with the help of the 1 H NMR spectrum as the aminothioborane with the tentatively suggested structure XIV: the signals of protons of the CH 2 group prove their nonequivalency on the basis of hindered rotation which is explained by the location of this CH 2 group in a five-membered ring of the chelate XlV.…”

Section: Ri=~n-ch;mentioning

confidence: 99%

Tricyclic psychotropic agents containing two chalcogen atoms in the central ring: Derivatives of 11H-dibenz[b,f]-1,4-oxathiepin

Šindelář

Holubek

Ryska

et al. 1982

Collect. Czech. Chem. Commun.

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Reactions of 2-bromobenzyl bromide and its analogues XVII and XXV with 2-hydroxythiophenol resulted in llH-dibenz[b,f]-1 ,4-oxat hiepin (Ia) and its 2-chloro (Ib) and 2-trifluoromethyl derivative (Ie). Treatment of the lithium compounds derived from Ia and Ib with carbon dioxide and dimethylaminoalkyl chlorides gave compounds IIa, Va and VIab; modification of the si de chains led to amines IVa, VIla and VIlla. 1l-(I-Methyl-4-piperidyl) derivatives Xbc were obtained by chlorination of compounds Ibc with sulfuryl chloride or N-chlorosuccinimide and the following treatment with I-methyl-4-piperidylmagnesium chloride. Compound Ib was transformed by oxidation to the sulfone XX affording by treatment with sodium hydride and tert-aminoalkyl chlorides the basic sulfones XXI and XXII. While the nucJeariy unsubstituted amines with the aliphatic side cha ins (IVa and VIla) have intensive antireserpine activity and a re potential antidepressants, the 1l-(I-methyl-4-piperidyl) derivatives with a substituent in position 2 of the skeleton (Xbc) are potential neuroleptics; the trifluoromethyl derivative Xc especially has outstanding cataleptic and antiapomorphine efficacy.In a recent communication! we outlined the project of searching after psychotropic agents among derivatives of the linearly condensed tricyclic systems with two chalcogen atoms in the central seven-membered ring and described the synthesis and pharmacology of several ll-(dimethylaminoalkyl) derivatives of ] IH-dibenzo[b, e]-1,4-dioxepin and llH-dibenzo[b, e]-l,4-dithiepin . The presently described synthesis of ll-(aminoalkyl) derivatives of llH-dibenz[b,f]-l,4-oxathiepin (fa) and its 2-chloro (f b) and 2-trifluoromethyl derivative (I c) is a continuation of this work. With the exception of our own preliminary communication 2 , dealing only with the synthesis of the basic compound la, the llH-dibenz[b,f]-1 ,4-oxathiepin system was not described in the literature.Compound la was obtained by two methods. The first one started from a reaction of 2-methoxythiophenol 3 with 2-bromobenzyl bromide 4 in an ethanolic solution of sodium hydroxide leading to 2-(2-bromobenzytthio )anisole (XII) which was de-Part CLXIV in the series Neurotropic and Psychotropic Agents; Part CLXIII: This Journal 47, 636 (1982).

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“…3a. Allen and Moir (1), in discussing the superiority of this synthetic route for the preparation of quadruply ortho-substituted diphenyl ethers, cited many failures of the Ullmann reaction (7,8) and showed that the lower requirements for activation (6,5) in the Hems synthesis make it more promising for the preparation of such highly hindered ortho-substituted diphenyl ethers than the well-known reaction of a phenol, a base, and an activated aryl halide (9-1 1).…”

Section: Synthesis Of Hindered Diphenyl Ethersmentioning

confidence: 99%

Synthesis of highly hindered diphenyl ethers

Neville¹,

Moir²

1969

Can. J. Chem.

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A new modification of the Hems synthesis for diphenyl ethers is reported. The preparation of 11 tetraortho-substituted, 12 tri-ortho-substituted, and 4 di-ortho-substituted diphenyl ethers is described for the action of various phenols on N-(4'-carbomethoxy-2',6'-dinitro)phenylpyridinium chloride. Some factors governing product formation are discussed on the basis of the extensive number of successful as well as unsuccessful reactions.

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The Chemistry of the Diaryl Ethers.

Cited by 32 publications

References 152 publications

Metal-free oxidative aromatization of 2-aryloxycyclohex-2-en-1-ones to 2-aryloxyphenols using DDQ/Amberlyst-15

Metal-free oxidative aromatization of 2-aryloxycyclohex-2-en-1-ones to 2-aryloxyphenols using DDQ/Amberlyst-15

Tricyclic psychotropic agents containing two chalcogen atoms in the central ring: Derivatives of 11H-dibenz[b,f]-1,4-oxathiepin

Synthesis of highly hindered diphenyl ethers

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