36779-79-0Relevant articles and documents
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.
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.
supporting information, (2020/06/04)
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%.
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.
OPEN-FLASK HYDROBORATION AND THE USE THEREOF
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Paragraph 0046; 0049; 0059; 0060; 0061, (2018/03/25)
The present disclosure generally relates to a process for hydroboration of an alkene or alkyne using ammonia borane (AB). In particular, the present invention relates to hydroboration of an alkene or alkyne in the presence of air or moisture, and a clean process for facile preparation of an alcohol by oxidizing the organoborane so formed with hydrogen peroxide. The products, including aminodialkylboranes, ammonia trialkylborane complexes, as well as various alcohols so prepared, are within the scope of this disclosure.
Microwave-assisted isomerizations of epoxides to allylic alcohols
Consiglio, Gabriella Barozzino,Mordini, Alessandro
, p. 447 - 454 (2018/05/22)
The present work reports a study on the isomerization reactions of several alkyl epoxides to the corresponding allylic alcohols or bicyclic alcohols under microwave irradiation. The reaction occurred in the presence of lithium diisopropylamide as a base and different experimental conditions in terms of solvent, amount of the base, times and temperatures. The traditional heating with an oil-bath and the use of alternative organometallic bases, as the Lochmann-Schlosser bases, have been furthermore compared with the microwave heating. The results obtained show that the use of microwave irradiations on promoting the isomerization of epoxides gives access to a series of synthetically useful products, among which allylic alcohols and bicyclic alcohols, depending on the starting substrate.
Bioorganometallic chemistry: Co-factor regeneration, enzyme recognition of biomimetic 1,4-NADH analogs, and organic synthesis; tandem catalyzed regioselective formation of N-substituted-1,4-dihydronicotinamide derivatives with [Cp*Rh(bpy)H]+, coupled to chiral S-alcohol formation with HLADH, and engineered cytochrome P450s, for selective C-H oxidation reactions
Lo, H. Christine,Ryan, Jessica D.,Kerr, John B.,Clark, Douglas S.,Fish, Richard H.
, p. 38 - 52 (2017/05/08)
Two novel tandem catalysis approaches for the chiral synthesis of S-alcohols from reduction of their prochiral ketones with Horse Liver Alcohol Dehydrogenase (HLADH), and selective C-H oxidation reactions with protein engineered Cytochrome P450s, are presented. We utilized a co-factor regeneration procedure with three biomimetic NAD+ models that do not contain the pyrophosphate, nor the adenosine group, and either/or a ribose, N-1-benzylnicotinamide triflate, 1, N-4-methoxybenzylnicotinamide triflate, 2, and β-nicotinamide-5′-ribose methyl phosphate, 3, in conjunction with in situ formed [Cp*Rh(bpy)H]+ from [Cp*Rh(bpy)(H2O)]2+ (Cp*?=?η5-C5Me5, bpy?=?2,2'-bipyridyl) and the hydride source, sodium formate, to regioselectively provide their 1,4-NADH analogs, N-benzyl-1,4-dihydronicotinamide, 4, N-4-methoxybenzyl-1,4-dihydronicotinamide, 5, and 1,4-dihydronicotinamide-5′-ribose methylphosphate, 6. Surprisingly, the 1,4-NADH biomimics, 4 and 6, were recognized, in the second tandem catalysis approach, by the natural 1,4-NADH dependent enzyme, HLADH, for catalyzed, highly enantioselective conversions of prochiral ketones to chiral S-alcohols. For example, with phenethylmethyl ketone and benzylmethyl ketone, the corresponding chiral alcohols were formed in >93% ee (S-enantiomer). Thus, 1,4-NADH biomimetic model recognition by HLADH does not significantly depend on the presence of the ribose, pyrophosphate, or adenosine groups to provide chiral products. We will also propose a plausible active site (HLADH)Zn-H intermediate, generated via a hydride transfer from bound 4/6 to Zn, for the enzymatic reduction of prochiral aryl/alkyl ketones to their chiral aryl/alkyl S-alcohols. Furthermore, the use of protein engineered cytochrome P450 enzymes provided improved molecular recognition of the above mentioned 1,4-NADH biomimetic co-factors, 4 and 5, for selective C-H oxidation reactions. For example, 1,4-NADH dependent mutants of natural 1,4-NAD(P)H dependent P450 BM-3 and 1,4-NADH dependent P450 CAM, with biomimetic co-factors 4 and 5, provided selective oxidation of p-nitrophenoxydecanoic acid to ω-oxydecanocarboxylic acid and p-nitrophenol, via C-H hydroxylation and β-hydrogen elimination, while oxidation of camphor provided hydroxycamphor, respectively. We will discuss the various parameters that effect molecular recognition of the biomimics, including protein engineering of both P450 BM-3 and P450 CAM enzymes, while determining the effect of the co-factor regeneration procedure on HLADH and P450 enzyme activity. These important observations have created new paradigms for the synthesis of organic compounds of interest, with the economically more favorable biomimics of NAD+, 1,4-NADH, and 1,4-NAD(P)H as co-factors, in tandem with the use of [Cp*Rh(bpy)(H)]+ as a regioselective catalytic reagent for co-factor regeneration.
Lipophilic oligopeptides for chemo- and enantioselective acyl transfer reactions onto alcohols
Mueller, Christian E.,Zell, Daniela,Hrdina, Radim,Wende, Raffael C.,Wanka, Lukas,Schuler, Soeren M. M.,Schreiner, Peter R.
, p. 8465 - 8484 (2013/09/24)
Inspired by the extraordinary selectivities of acylases, we envisioned the use of lipophilic oligopeptidic organocatalysts for the acylative kinetic resolution/desymmetrization of rac- and meso-cycloalkane-1,2-diols. Here we describe in a full account the discovery and development process from the theoretical concept to the final catalyst, including scope and limitations. Competition experiments with various alcohols and electrophiles show the full potential of the employed oligopeptides. Additionally, we utilized NMR and IR-spectroscopic methods as well as computations to shed light on the factors responsible for the selectivity. The catalyst system can be readily modified to a multicatalyst by adding other catalytically active amino acids to the peptide backbone, enabling the stereoselective one-pot synthesis of complex molecules from simple starting materials.
