- Cationic Dirhodium Complexes Bridged by 2-Phosphinopyridines Having an Exquisitely Positioned Axial Shielding Group: A Molecular Design for Enhancing the Catalytic Activity of the Dirhodium Core
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This report describes a strategy to create highly electrophilic dirhodium catalysts. The electrophilicity of lantern-Type dirhodium complexes is generally decreased by the coordination of a ligand to the axial site, which often causes a reduction in the catalytic activity. We designed and synthesized a series of cationic dirhodium complexes bridged by 2-diarylphosphinopyridines having a bulky 2,4,6-Triisopropylphenyl (Tip) group that can prevent the attack of external molecules to the closest axial site. Theoretical calculations indicated that the Tip group weakly interacts with the axial site but hardly reduces the electrophilicity of the dirhodium core. The complexes served as excellent catalyst precursors for the dehydrogenative silylation of alcohols using hydrosilanes under mild conditions and a low metal loading, producing the silyl ethers in higher yields in comparison to conventional dirhodium complexes.
- Ohnishi, Ryuhei,Ohta, Hidetoshi,Mori, Shigeki,Hayashi, Minoru
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p. 2678 - 2690
(2021/07/31)
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- Synthetic Versatility of Lipases: Application for Si-O Bond Formation and Cleavage
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Several commercially available lipases were examined in a study on O-Si bond formation and cleavage applying silicon-based protecting groups and alcohols or the corresponding silyl ethers. With regard to deprotection, from silyl ether to the corresponding alcohol, only the solvent and the lipase were necessary. The influence of the protecting group, the lipase source, and the substituent was investigated to optimize the results. The TMS moiety could be removed in 24 hours of reaction at room temperature in aqueous systems (conv. up to 99%, depending on the substrate and lipase). The reverse reactions, that is, with the protection of the alcohols, were carried out in hexane using different silyl chlorides. The TMS, TES, and TBS moieties were successfully inserted in the primary and secondary alcohols without the need for dry conditions or an inert atmosphere, presenting conversions of up to 99%, depending on the substrate.
- Brondani, Patrícia Bulegon,Mittersteiner, Mateus,Voigt, Morgana Aline,Klinkowski, Bruna Heloisa,Riva Scharf, Dilamara,De Jesus, Paulo Cesar
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supporting information
p. 477 - 485
(2019/01/10)
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- FLP-Catalyzed Transfer Hydrogenation of Silyl Enol Ethers
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Herein we report the first catalytic transfer hydrogenation of silyl enol ethers. This metal free approach employs tris(pentafluorophenyl)borane and 2,2,6,6-tetramethylpiperidine (TMP) as a commercially available FLP catalyst system and naturally occurring γ-terpinene as a dihydrogen surrogate. A variety of silyl enol ethers undergo efficient hydrogenation, with the reduced products isolated in excellent yields (29 examples, 82 % average yield).
- Khan, Imtiaz,Reed-Berendt, Benjamin G.,Melen, Rebecca L.,Morrill, Louis C.
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p. 12356 - 12359
(2018/09/18)
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- 4-(N,N-dimethylamino)pyridine-embedded nanoporous conjugated polymer as a highly active heterogeneous organocatalyst
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We report herein for the first time the incorporation of a versatile organocatalyst, 4-(N,N-dimethylamino)pyridine (DMAP), into the network of a nanoporous conjugated polymer (NCP) by the "bottom-up" approach. The resulting DMAP-NCP material possesses highly concentrated and homogeneously distributed DMAP catalytic sites (2.02 mmol g-1). DMAP-NCP also exhibits enhanced stability and permanent porosity due to the strong covalent linkage and the rigidity of the "bottom-up" monomers. As a result, DMAP-NCP shows excellent catalytic activity in the acylation of alcohols with yields of 92-99 %. The DMAP-NCP catalyst could be easily recovered from the reaction mixture and reused in at least 14 consecutive cycles without measurable loss of activity. Moreover, the catalytic acylation reaction could be performed under neat and continuous-flow conditions for at least 536 h of continuous work with the same catalyst activity. Copyright
- Zhang, Yuan,Zhang, Yong,Sun, Ya Lei,Du, Xin,Shi, Jiao Yi,Wang, Wei,Wang, Wei David
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experimental part
p. 6328 - 6334
(2012/06/18)
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- InCl3/Me3SiBr-catalyzed direct coupling between silyl ethers and enol acetates
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A combined Lewis acid catalyst of InCl3 and Me3SiBr promoted the direct use of enol acetates in the coupling with low-reactive silyl ethers, in which functional groups including ketones and aldehydes survived. Sterically hindered silyl ethers such as ROSiEt3, ROSiPh3, ROSit-BuMe2, and ROSii-Pr3 were also applicable.
- Onishi, Yoshiharu,Nishimoto, Yoshihiro,Yasuda, Makoto,Baba, Akio
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supporting information; experimental part
p. 2762 - 2765
(2011/08/02)
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- Selective oxidation of benzylic alcohols and TBDMS ethers to carbonyl compounds with CrO3-H5IO6
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Benzyl alcohols and benzyl TBDMS ethers were efficiently oxidized to the corresponding carbonyl compounds in high yield with periodic acid catalyzed by CrO3 at low temperature (-78°C). The oxidation procedure was highly functional group tolerant and very selective for the TBDMS group over the TBDPS group. Georg Thieme Verlag Stuttgart.
- Zhang, Suhong,Xu, Liang,Trudell, Mark L.
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p. 1757 - 1760
(2007/10/03)
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- A Convenient Method for Protection and Deprotection of Alcohols and Phenols as Alkylsilyl Ethers Catalyzed by Iodine under Microwave Irradiation
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Irradiation of alcohols or phenols with tert-butyldimethylsilyl chloride (TBDMSCl) or trimethylsilyl chloride (TMSCl) in presence of catalytic amount (20 mol%) of iodine in a microwave oven for 2 min gives the corresponding silyl ethers in excellent yield. Iodine in methanol deprotects the silyl ether into its parent alcohol or phenol under similar reaction conditions.
- Saxena, Ira,Deka, Nabajyoti,Sarma, Jadab C.,Tsuboi, Sadao
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p. 4185 - 4191
(2007/10/03)
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- Electron-Rich 0 = PR3 compounds: Catalysts for alcohol silylation
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The catalytic effect of a group of R3P = O compounds was studied in a mild procedure for the silylation of primary alcohols, secondary alcohols, hindered secondary alcohols, and of hindered phenols in the presence of t-butyldimethylsilyl chlori
- Liu, Xiaodong,Verkade, John G.
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- Efficient and chemoselective protection of alcohols and phenols with tert-butyldimethylchlorosilane (TBDMCS) under solvent-free conditions
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Various types of primary and secondary alcohols and phenols can be converted efficiently to their corresponding TBDMS ethers using TBDMCS/imidazole under solvent-free conditions. Elimination of DMF, accompanied with an easy non-aqueous work-up and a high rate enhancement of the reaction are worthy to be mentioned for the presented method. The reactions show absolute chemoselectivity for the protection of primary in the presence of secondary alcohols.
- Firouzabadi, Habib,Etemadi, Shahrad,Karimi, Babak,Jarrahpour, Ali Asghar
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- Nonionic superbase-catalyzed silylation of alcohols
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Herein we report a very effective and mild procedure for the silyl protection of a wide variety of substrate alcohols, including primary, secondary, allylic, propargylic, benzylic, hindered secondary, tertiary, acid-sensitive, and base-sensitive alcohols and also hindered phenols. The silylation reagent used is tert-butyldimethylsilyl chloride (TBDMSCl) and the catalyst is P(MeNCH2CH2)3N, 1b, both of which are commercially available. The reactions are carried out in acetonitrile from 24 to 40 °C and on rare occasions in DMF from 24 to 80 °C. The effect of solvent, catalyst concentration, and temperature and reaction time on the silylation of alcohols and the excellent compatibility of our method with a variety of functional groups is discussed. An efficient method for recycling the catalyst is also presented. Although representative primary alcohols, secondary alcohols, and phenols were silylated using the more sterically hindered reagent tert-butyldiphenylsilyl chloride (TBDPSCl) in the presence of lb as a catalyst, tertiary alcohols were recovered unchanged.
- D'Sa, Bosco A.,McLeod, Dale,Verkade, John G.
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p. 5057 - 5061
(2007/10/03)
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- A novel method for direct conversion of tetrahydropyranyl ethers into t-butyldimethylsilyl ethers with t-butyldimethylsilyl triflate and dimethyl sulfide
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Direct conversion of THP ethers into TBS ethers has been achieved with TBSOTf and dimethyl sulfide in dichloromethane.
- Kim,Kee
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p. 2899 - 2900
(2007/10/02)
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- The Utility of t-Butyldimethylsilane as an Effective Silylation Reagent for the Protection of Functional Groups
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Treatment of compounds containing functional groups, such as alcohols, amines, and carboxylic acids, with t-butyldimethylsilane in the presence of a catalytic amount of palladium on carbon is described to provide a new, convenient method for the introduction of a t-butyldimethylsilyl (TBDMS) group.
- Yamamoto, Keiji,Takemae, Makoto
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p. 2111 - 2113
(2007/10/02)
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- 1,1,3,3-TETRAMETHYLGUANIDINE: AN EFFECTIVE CATALYST FOR THE t-BUTYLDIMETHYLSILYLATION OF ALCOHOLS
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Reaction of alcohols with equimolar amounts of t-butyldimethylchlorosilane and triethylamine in the presence of 1,1,3,3-tetramethylguanidine as a catalyst affords the t-butyldimethylsilyl ethers in high yields.
- Kim, Sunggak,Chang, Heung
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p. 899 - 904
(2007/10/02)
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