1632-68-4Relevant academic research and scientific papers
Reexamination of diisobutylaluminum hydride as a stereoselective reducing agent for reduction of cyclic ketones to thermodynamically more stable alcohols
Cha, Jin Soon,Kwon, Oh Oun,Kim, Jong Mi,Cho, Sung Dong
, p. 1465 - 1466 (1997)
The reducing property of diisobutylaluminum hydride (DIBAH) has been reexamined as a stereoselective reducing agent for reduction of representative cyclic ketones. When the reduction of excess cyclic ketone with DIBAH was carried out at 0°C in ethyl ether, only 1 equiv of the free hydride was involved to show a low stereoselectivity. However, when performed at 25°C or under reflux in ethyl ether, one isobutyl group as well as the free hydride was also involved in this reduction: the first equiv of ketone was reduced rapidly and the second one reduced, in a relatively slow rate. In addition, the stereoselectivity increases consistently with increase of reaction time to afford the thermodynamically more stable isomer alcohols exclusively.
RHODIUM(I)-CATALYZED ASYMMETRIC HYDROBORATION OF ALKENES WITH 1,3,2-BENZODIOXABOROLE
Sato, Makoto,Miyaura, Norio,Suzuki, Akira
, p. 231 - 234 (1990)
Several rhodium(I) complexes containing chiral phosphine, (+)DIOP, (+)BINAP, (S,S) CHIRAPHOS, and (S)(R)BPPFA, have been found to be effective as catalyst for the asymmetric hydroboration of prochiral alkenes with catecholborane (1,3,2-benzodioxaborole) to give optically active 2-alkyl-1,3,2-benzodioxaboroles. among the ligands examined, DIOP has been recognized to be most effective to give high asymmetric induction.
Use of achiral (diphosphine)RuCl2(diamine) precatalysts as a practical alternative to sodium borohydride for ketone reduction
De Koning, Pieter D.,Jackson, Mark,Lennon, Ian C.
, p. 1054 - 1058 (2006)
Stoichiometric sodium borohydride is frequently used in the chemoselective reduction of ketones to racemic secondary alcohols. Catalytic homogeneous hydrogenation using (diphosphine)RuCl2(diamine) complexes provides a practical and economic alternative. A range of substrates were investigated and the optimum precatalyst identified in each case. Norcamphor was reduced with high diastereoselectivity using (Ph3P)2-RuCl 2(en); (E)-4-phenylbut-3-en-2-one was reduced with good chemoselectivity, and acetophenone was hydrogenated very efficiently using the same precatalyst. Isophorone and 3-dimethylaminopropiophenone were effectively hydrogenated using (dppf)RuCl2(en).
A short asymmetric synthesis of methyl 2-((1S,3R)-3-((tert-butyldiphenylsilyl)oxy)cyclopentyl)acetate from norbornene
Huang, Buwen,Elleraas, Jeff,Ewanicki, Jason,Sutton, Scott C.
, (2020)
Methyl 2-((1S,3R)-3-((tert-butyldiphenylsilyl)oxy)cyclopentyl)acetate has been synthesized from norbornene using Hayashi's (S)-MOP Pd-catalyzed asymmetric hydrosilation. On a 1 mol scale, asymmetric hydrosilation of norbornene afforded an 84:16 exo- to endo-norborneol mixture but with exclusive 1R,4S-stereochemistry at the bridgehead carbons. The norborneol mixture was converted to an optically pure chiral bicyclic lactone via a high-yielding tandem oxidation/Baeyer-Villiger reaction. Acid-promoted ring-opening of the lactone followed by immediate silyl protection afforded the chiral cis-1,3-cyclopentane intermediate in five steps with an overall yield of 41%.
Asymmetric Functionalization of Bicycloalkenes by Catalytic Enantioposition-Selective Hydrosilylation
Uozumi, Yasuhiro,Lee, Sang-Yong,Hayashi, Tamio
, p. 7185 - 7188 (1992)
Hydrosilylation of norbornene with trichlorosilane in the presence of palladium catalyst (0.01-0.1 mol percent) coordinated with (R)-MOP ligand gave a quantitative yield of exo-2-trichlorosilylnorbornane, which was oxidized with hydrogen peroxide to give (1S,2S,4R)-exo-2-norbornanol in 96percent ee.The similar hydrosilylation and oxidation of endo-5,6-dicarbomethoxy-2-norbornene, bicyclooctene, and norbornadiene gave the corresponding bicyclic alcohols of 94percent ee, 92percent ee, and 95percent ee, respectively.
Chemoselective Cleavage of Si-C(sp3) Bonds in Unactivated Tetraalkylsilanes Using Iodine Tris(trifluoroacetate)
Matsuoka, Keitaro,Komami, Narumi,Kojima, Masahiro,Mita, Tsuyoshi,Suzuki, Kimichi,Maeda, Satoshi,Yoshino, Tatsuhiko,Matsunaga, Shigeki
supporting information, p. 103 - 108 (2021/01/13)
Organosilanes are synthetically useful reagents and precursors in organic chemistry. However, the typical inertness of unactivated Si-C(sp3) bonds under conventional reaction conditions has hampered the application of simple tetraalkylsilanes in organic synthesis. Herein we report the chemoselective cleavage of Si-C(sp3) bonds of unactivated tetraalkylsilanes using iodine tris(trifluoroacetate). The reaction proceeds smoothly under mild conditions (-50 °C to room temperature) and tolerates various polar functional groups, thus enabling subsequent Tamao-Fleming oxidation to provide the corresponding alcohols. NMR experiments and density functional theory calculations on the reaction indicate that the transfer of alkyl groups from Si to the I(III) center and the formation of the Si-O bond proceed concertedly to afford an alkyl-λ3-iodane and silyl trifluoroacetate. The developed method enables the use of unactivated tetraalkylsilanes as highly stable synthetic precursors.
Generalized Chemoselective Transfer Hydrogenation/Hydrodeuteration
Wang, Yong,Cao, Xinyi,Zhao, Leyao,Pi, Chao,Ji, Jingfei,Cui, Xiuling,Wu, Yangjie
supporting information, p. 4119 - 4129 (2020/08/10)
A generalized, simple and efficient transfer hydrogenation of unsaturated bonds has been developed using HBPin and various proton reagents as hydrogen sources. The substrates, including alkenes, alkynes, aromatic heterocycles, aldehydes, ketones, imines, azo, nitro, epoxy and nitrile compounds, are all applied to this catalytic system. Various groups, which cannot survive under the Pd/C/H2 combination, are tolerated. The activity of the reactants was studied and the trends are as follows: styrene'diphenylmethanimine'benzaldehyde'azobenzene'nitrobenzene'quinoline'acetophenone'benzonitrile. Substrates bearing two or more different unsaturated bonds were also investigated and transfer hydrogenation occurred with excellent chemoselectivity. Nano-palladium catalyst in situ generated from Pd(OAc)2 and HBPin extremely improved the TH efficiency. Furthermore, chemoselective anti-Markovnikov hydrodeuteration of terminal aromatic olefins was achieved using D2O and HBPin via in situ HD generation and discrimination. (Figure presented.).
Erbium-Catalyzed Regioselective Isomerization-Cobalt-Catalyzed Transfer Hydrogenation Sequence for the Synthesis of Anti-Markovnikov Alcohols from Epoxides under Mild Conditions
Liu, Xin,Longwitz, Lars,Spiegelberg, Brian,T?njes, Jan,Beweries, Torsten,Werner, Thomas
, p. 13659 - 13667 (2020/11/30)
Herein, we report an efficient isomerization-transfer hydrogenation reaction sequence based on a cobalt pincer catalyst (1 mol %), which allows the synthesis of a series of anti-Markovnikov alcohols from terminal and internal epoxides under mild reaction conditions (≤55 °C, 8 h) at low catalyst loading. The reaction proceeds by Lewis acid (3 mol % Er(OTf)3)-catalyzed epoxide isomerization and subsequent cobalt-catalyzed transfer hydrogenation using ammonia borane as the hydrogen source. The general applicability of this methodology is highlighted by the synthesis of 43 alcohols from epoxides. A variety of terminal (23 examples) and 1,2-disubstituted internal epoxides (14 examples) bearing different functional groups are converted to the desired anti-Markovnikov alcohols in excellent selectivity and yields of up to 98%. For selected examples, it is shown that the reaction can be performed on a preparative scale up to 50 mmol. Notably, the isomerization step proceeds via the most stable carbocation. Thus, the regiochemistry is controlled by stereoelectronic effects. As a result, in some cases, rearrangement of the carbon framework is observed when tri-and tetra-substituted epoxides (6 examples) are converted. A variety of functional groups are tolerated under the reaction conditions even though aldehydes and ketones are also reduced to the respective alcohols under the reaction conditions. Mechanistic studies and control experiments were used to investigate the role of the Lewis acid in the reaction. Besides acting as the catalyst for the epoxide isomerization, the Lewis acid was found to facilitate the dehydrogenation of the hydrogen donor, which enhances the rate of the transfer hydrogenation step. These experiments additionally indicate the direct transfer of hydrogen from the amine borane in the reduction step.
Potential Synthetic Adaptogens: V. Synthesis of Cage Monoamines by the Schwenk–Papa Reaction
Brunilin, R. V.,Mkrtchyan, A. S.,Nawrozkij, M. B.,Novakov, I. A.,Vernigora, A. A.,Voloboev, S. N.,Vostrikova, O. V.
, p. 1742 - 1748 (2020/01/11)
The reduction of cage ketoximes under Schwenk–Papa reaction conditions was studied to establish that the d,l, d- and l-camphor oximes are smoothly reduced to the corresponding amines in high yields. At the same time, d,l-norcamphor and adamantan-2-one oximes undergo partial catalytic deoximation to form a mixture of the corresponding amines and alcohols.
Scalable and safe synthetic organic electroreduction inspired by Li-ion battery chemistry
Peters, Byron K.,Rodriguez, Kevin X.,Reisberg, Solomon H.,Beil, Sebastian B.,Kawamata, Yu,Baran, Phil S.,Hickey, David P.,Klunder, Kevin,Gorey, Timothy J.,Anderson, Scott L.,Minteer, Shelley D.,Collins, Michael,Starr, Jeremy,Chen, Longrui,Udyavara, Sagar,Neurock, Matthew
, p. 838 - 845 (2019/04/30)
Reductive electrosynthesis has faced long-standing challenges in applications to complex organic substrates at scale. Here, we show how decades of research in lithium-ion battery materials, electrolytes, and additives can serve as an inspiration for achieving practically scalable reductive electrosynthetic conditions for the Birch reduction. Specifically, we demonstrate that using a sacrificial anode material (magnesium or aluminum), combined with a cheap, nontoxic, and water-soluble proton source (dimethylurea), and an overcharge protectant inspired by battery technology [tris(pyrrolidino)phosphoramide] can allow for multigram-scale synthesis of pharmaceutically relevant building blocks. We show how these conditions have a very high level of functional-group tolerance relative to classical electrochemical and chemical dissolving-metal reductions. Finally, we demonstrate that the same electrochemical conditions can be applied to other dissolving metal-type reductive transformations, including McMurry couplings, reductive ketone deoxygenations, and epoxide openings.
