- Catalytic Activation of Unstrained C(Aryl)-C(Alkyl) Bonds in 2,2′-Methylenediphenols
-
Catalytic activation of unstrained and nonpolar C-C bonds remains a largely unmet challenge. Here, we describe our detailed efforts in developing a rhodium-catalyzed hydrogenolysis of unstrained C(aryl)-C(alkyl) bonds in 2,2′-methylenediphenols aided by removable directing groups. Good yields of the monophenol products are obtained with tolerating a wide range of functional groups. In addition, the reaction is scalable, and the catalyst loading can be reduced to as low as 0.5 mol %. Moreover, this method proves to be effective to cleave C(aryl)-C(alkyl) linkages in both models of phenolic resins and commercial novolacs resins. Finally, detailed experimental and computational mechanistic studies show that with C-H activation being a competitive but reversible off-cycle reaction, this transformation goes through a directed C(aryl)-C(alkyl) oxidative addition pathway.
- Dong, Guangbin,Ratchford, Benjamin L.,Xue, Yibin,Zhang, Rui,Zhu, Jun
-
p. 3242 - 3249
(2022/02/23)
-
- Catalytic activation of unstrained C(aryl)–C(aryl) bonds in 2,2′-biphenols
-
Transition metal catalysis has emerged as an important means for C–C activation that allows mild and selective transformations. However, the current scope of C–C bonds that can be activated is primarily restricted to either highly strained systems or more polarized C–C bonds. In contrast, the catalytic activation of non-polar and unstrained C–C moieties remains an unmet challenge. Here we report a general approach for the catalytic activation of the unstrained C(aryl)–C(aryl) bonds in 2,2′-biphenols. The key is to utilize the phenol moiety as a handle to install phosphinites as a recyclable directing group. Using hydrogen gas as the reductant, monophenols are obtained with a low catalyst loading and high functional group tolerance. This approach is also applied to the synthesis of 2,3,4-trisubstituted phenols. A further mechanistic study suggests that the C–C activation step is mediated by a rhodium(i) monohydride species. Finally, a preliminary study on breaking the inert biphenolic moieties in lignin models is illustrated.
- Zhu, Jun,Wang, Jianchun,Dong, Guangbin
-
-
- o-xylylene bis(triethyl ammonium tribromide) as a mild and recyclable reagent for rapid and regioselective bromination of anilines and phenols
-
Background: o-Xylylene bis(triethyl ammonium tribromide) (OXBTEATB) as a recyclable and high bromine containing di-(tribromide) reagent has been employed for the bromination of various organic substrates such as phenol and aniline or its derivatives. This catalyst can be recovered and reused several times. Methods: Aryl bromides shown in Table 1, were easily produced from bromination of aromatic compounds by OXBTEATB. This high-yield process lets the reagents to be recycled and reused. Results: As shown in Table 1, substituted anilines, phenols and β-naphthol were found to be the most reactive and immediately converted to the corresponding mono-brominated products by OXBTEATB. Conclusion: OXBTEATB can be considered a solidified bromine. This novel reagent has variable solubility in different polar protic and aprotic solvents but insoluble in non-polar aprotic solvent. Subsequently, OXBTEATB can be recognized as a more useful brominating and regioselective catalyst than the liquid bromine.
- Hemati, Roya,Shahvelayati, Ashraf S.,Yadollahzadeh, Khadijeh
-
p. 682 - 687
(2018/07/14)
-
- NEW THIENOPYRIMIDINE DERIVATIVES, A PROCESS FOR THEIR PREPARATION AND PHARMACEUTICAL COMPOSITIONS CONTAINING THEM
-
Compounds of formula (I): wherein R1, R2, R3, R4, R5, R6, R7, R12, X, A and n are as defined in the description.
- -
-
Page/Page column 90
(2015/07/15)
-
- Synthesis and antioxidant activity of 5-hydroxycoumarans,c 6-hydroxychromanes and sulfur-containing derivatives on their base
-
A synthesis of 5-hydroxycoumarans, 6-hydroxychromanes and their dodecylthiomethyl- substituted derivatives was accomplished based on methylphenols through the intermediate preparation of 2-allyl-4-alkoxyphenols. The sulfur-containing compounds synthesized
- Yagunov,Khol'shin,Kandalintseva,Prosenko
-
p. 1395 - 1400
(2014/05/06)
-
- Nickel-catalyzed decarbonylative polymerization of 5-alkynylphthalimides: A new methodology for the preparation of polyheterocycles
-
A nickel-catalyzed decarbonylative cycloaddition was developed, in which 5-alkynylphthalimides reacted to afford a new type of polyisoquinolone. It was demonstrated for the first time that decarbonylative cycloaddition can be an elementary process of polycondensation for the preparation of heterocyclic polymers.
- Takeuchi, Makoto,Kurahashi, Takuya,Matsubara, Seijiro
-
supporting information
p. 1566 - 1568
(2013/01/15)
-
- Efficient and regioselective bromination of aromatic compounds with ethylenebis(N-methylimidazolium) ditribromide (EBMIDTB)
-
A regioselective and highly efficient method for bromination of phenol and aniline derivatives using ethylenebis(N-methylimidazolium) ditribromide (EBMIDTB) as an efficient reagent in dichloromethane at ambient temperature is reported. The reagent can be recovered and reused several times.
- Hosseinzadeh, Rahman,Tajbakhsh, Mahmood,Mohadjerani, Maryam,Lasemi, Zahra
-
experimental part
p. 868 - 876
(2010/05/18)
-
- First synthesis of nitro-substituted 2,2-diphenyl-2H-1-benzopyrans via the ipso-nitration reaction
-
The first synthesis of a series of nitro-substituted 2,2-diphenyl-2H-1-benzopyrans is reported. Our synthetic approach is based on a linear synthesis in two steps from appropriate brominated 2,2-diphenyl-2H-1-benzopyrans 12-17, which requires the preliminary preparation of bromophenols 7-11. These latter were easily obtained by the reaction of phenols 1-5 with a mild and selective brominating agent tetrabutylammonium tribromide (TBA·Br3). The key intermediates 12-17 were efficiently elaborated through an univocal classic chromenization between the commercially available 1,1-diphenyl-2-yn-1-ol and the brominated phenols 6-11. The compounds 12-17 so obtained were converted into arylboronic acids 18-23 by a metalation/boronylation sequence, followed by acid hydrolysis. From advanced building blocks 18-23, the introduction of nitro group, which constitutes the ultimate step of our strategy, was achieved by an ipso-nitration reaction using the Crivello's reagent. This highly selective method provides only the ipso-nitrated products 24-29 in moderate to high yield.
- Bougdid, Lahoussine,Heynderickx, Arnault,Delbaere, Stéphanie,Moustrou, Corinne
-
p. 8242 - 8249
(2008/02/05)
-
- Studies towards the total synthesis of mumbaistatin: Synthesis of highly substituted benzophenone and anthraquinone building blocks
-
Model compounds and building blocks for a planned total synthesis of the highly potent glucose-6-phosphate (G6P) translocase inhibitor mumbaistatin (1) and structural analogs were elaborated: compound 1 represents a lead structure in the development of po
- Kaiser, Florian,Schwink, Lothar,Velder, Janna,Schmalz, Hans-Günther
-
p. 3201 - 3217
(2007/10/03)
-
- 4-(1-benzoylindol-3-yl)butyric acids and FK143: Novel nonsteroidal inhibitors of steroid 5α-reductase (II)
-
A novel series of indolebutyric acids with varying benzoyl substituents were synthesized to develop nonsteroidal inhibitors of steroid 5α-reductase. We previously reported the discovery of a novel nonsteroidal 5α-reductase inhibitor, FR119680, which had a
- Sawada, Kozo,Okada, Satoshi,Golden, Patrick,Kayakiri, Natsuko,Sawada, Yuki,Hashimoto, Masashi,Tanaka, Hirokazu
-
p. 481 - 491
(2007/10/03)
-
- Halogenation Using Quaternary Ammonium Polyhalides. IV. Selective Bromination of Phenols by Use of Tetraalkylammonium Tribromides
-
Reaction of phenols with calculated amounts of benzyltrimethylammonium tribromide or tetrabutylammonium tribromide in dichloromethane-methanol for 0.5-1 h under mild conditions gave, selectively, the objective mono-, di-, or tribromophenols in good yields.
- Kajigaeshi, Shoji,Kakinami, Takaaki,Okamoto, Tsuyoshi,Nakamura, Hiroko,Fujikawa, Masahiro
-
p. 4187 - 4189
(2007/10/02)
-
