- A remarkable solvent effect toward the Pd/C-catalyzed cleavage of silyl ethers
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Selective hydrogenation conditions of olefin, benzyl ether and acetylene functionalities in the presence of TBDMS or TES ether have been developed.
- Sajiki, Hironao,Ikawa, Takashi,Hattori, Kazuyuki,Hirota, Kosaku
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Read Online
- Umpolung Strategy for Arene C?H Etherification Leading to Functionalized Chromanes Enabled by I(III) N-Ligated Hypervalent Iodine Reagents
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The direct formation of aryl C?O bonds via the intramolecular dehydrogenative coupling of a C?H bond and a pendant alcohol represents a powerful synthetic transformation. Herein, we report a method for intramolecular arene C?H etherification via an umpoled alcohol cyclization mediated by an I(III) N-HVI reagent. This approach provides access to functionalized chromane scaffolds from primary, secondary and tertiary alcohols via a cascade cyclization-iodonium salt formation, the latter providing a versatile functional handle for downstream derivatization. Computational studies support initial formation of an umpoled O-intermediate via I(III) ligand exchange, followed by competitive direct and spirocyclization/1,2-shift pathways. (Figure presented.).
- Mikhael, Myriam,Guo, Wentao,Tantillo, Dean J.,Wengryniuk, Sarah E.
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supporting information
p. 4867 - 4875
(2021/09/14)
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- Harnessing the Power of the Asymmetric Grignard Synthesis of Tertiary Alcohols: Ligand Development and Improved Scope Exemplified by One-Step Gossonorol Synthesis
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A series of N-substituted cyclohexyldiaminophenolic ligands for the asymmetric Grignard synthesis of tertiary alcohols is reported. The 2,5-dimethylpyrrole-decorated ligand led to improved enantioselectivities and broadened the scope of the methodology. As an exemplar, we report an unprecedented highly selective one-step synthesis of gossonorol in 93% ee, also constituting the shortest formal syntheses of natural products boivinianin B and yingzhaosu C.
- Gilheany, Declan G.,Kavanagh, Saranna E.
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supporting information
p. 8198 - 8203
(2020/11/18)
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- Synergistic Catalysis for the Umpolung Trifluoromethylthiolation of Tertiary Ethers
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The first transition-metal-free, site-specific umpolung trifluoromethylthiolation of tertiary alkyl ethers has been developed, achieving the challenging tertiary C(sp3)–SCF3 coupling under redox-neutral conditions. The synergism of organophotocatalyst 4CzIPN and BINOL-based phosphorothiols can site-selectively cleave tertiary sp3 C(sp3)–O ether bonds in complex molecules initiated by a polarity-matching hydrogen-atom-transfer (HAT) event. The incorporation of several competing benzylic and methine C(sp3)?H bonds in alkyl ethers has little influence on the regioselectivity. Selective difluoromethylthiolation of C?O bonds has also been achieved. This represents not only an important step forward in trifluoromethylthiolation but also a promising means for site-selective C?O bond functionalization of unsymmetrical tertiary alkyl ethers.
- Xu, Wentao,Ma, Junyang,Yuan, Xiang-Ai,Dai, Jie,Xie, Jin,Zhu, Chengjian
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supporting information
p. 10357 - 10361
(2018/08/06)
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- Mechanochemical ritter reaction: A rapid approach to functionalized amides at room temperature
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A fast and efficient mechanochemical Ritter reaction between alcohols and nitriles under mild conditions is demonstrated. The reaction proceeds rapidly at room temperature in a solvent-free or low-solvent environment by using a Br?nsted acid catalyst. Its general application has been verified through a substrate screening comprising a wide range of functionalized nitriles as well as secondary and tertiary alcohols. Gentle Ritter: A fast and efficient mechanochemical Ritter reaction under mild conditions is described. The reaction proceeds rapidly at room temperature in a solvent-free or low-solvent environment by using sulfuric acid as catalyst.
- Dokli, Irena,Gredi?ak, Matija
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supporting information
p. 2727 - 2732
(2015/04/27)
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- PROCESS FOR THE PREPARATION OF CYCLOHEXYL-SUBSTITUTED TERTIARY ALKANOLS
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The present invention relates to processes for the preparation of compounds of the formula (Ia) by reacting styrene with a secondary alkanol and the hydrogenation of the resulting phenyl-substituted tertiary alkanol. In addition, the invention relates to compounds of the formula (Ia) and to the use of such compounds as fragrances, and also to compositions which comprise compounds of the formulae (Ia) and (Ib).
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Paragraph 0081-0082
(2014/06/24)
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- Solvent-modulated Pd/C-catalyzed deprotection of silyl ethers and chemoselective hydrogenation
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Recently we have reported undesirable and frequent deprotection of the TBDMS protective group of a variety of hydroxyl functions occurred under neutral and mild hydrogenation conditions using 10% Pd/C in MeOH. The deprotection of silyl ethers is susceptible to significant solvent effect. TBDMS and TES protecting groups were selectively cleaved in the presence of acid-sensitive functional groups such as TIPS ether, TBDPS ether and dimethyl acetal under hydrogenation condition using 10% Pd/C in MeOH. In contrast, chemoselective hydrogenation of reducible functional groups such as acetylene, olefin and benzyl ether, proceeds in the presence of TBDMS or TES ethers in AcOEt or MeCN.
- Ikawa, Takashi,Hattori, Kazuyuki,Sajiki, Hironao,Hirota, Kosaku
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p. 6901 - 6911
(2007/10/03)
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- A facile and highly efficient route to a traceless pi-arene chromium linker. Applications to synthetic and combinatorial chemistry.
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[reaction--see text] A simple and efficient method for the attachment of functionalized arene chromium carbonyls to a polymeric support has been developed. A highly efficient solid-phase synthesis of tertiary alcohols and esters was performed in a traceless manner using this strategy. The linker-fabrication protocol permits simultaneous immobilization of various substrates on the solid support.
- Rigby,Kondratenko
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p. 3683 - 3686
(2007/10/03)
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- INTRAMOLECULAR CYCLOALKYLATION OF PHENYLALKANOLS IN THE PRESENCE OF SULFURIC ACID
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Te distribution of the deuterium in the benzocyclenes formed during the intermolecular cycloalkylation of 2-R-4-phenyl-2-butanol (R=CD3, CD2CH3, CH2CD3) in the presence of 85percent sulfuric acid was investigated by NMR spectroscopy and mass spectrometry.Hydrogen exchange takes place at the stage of formation of the γ-phenylalkyl cation, the average lifetime of which is sufficient for the establishment of an isotopic equilibrium by successive elimination addition of an deuteron.
- Sakhabutdinov, A.G.,Usmanova, A.G.,Proidakov, A.G.,Bazhenov, B.A.,Schmidt, F.K.
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p. 1525 - 1529
(2007/10/02)
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