937-07-5Relevant articles and documents
Platinum-Catalyzed α,β-Desaturation of Cyclic Ketones through Direct Metal–Enolate Formation
Chen, Ming,Dong, Guangbin
supporting information, p. 7956 - 7961 (2021/03/01)
The development of a platinum-catalyzed desaturation of cyclic ketones to their conjugated α,β-unsaturated counterparts is reported in this full article. A unique diene-platinum complex was identified to be an efficient catalyst, which enables direct metal-enolate formation. The reaction operates under mild conditions without using strong bases or acids. Good to excellent yields can be achieved for diverse and complex scaffolds. A wide range of functional groups, including those sensitive to acids, bases/nucleophiles, or palladium species, are tolerated, which represents a distinct feature from other known desaturation methods. Mechanistically, this platinum catalysis exhibits a fast and reversible α-deprotonation followed by a rate-determining β-hydrogen elimination process, which is different from the prior Pd-catalyzed desaturation method. Promising preliminary enantioselective desaturation using a chiral-diene-platinum complex has also been obtained.
Bidentate Nitrogen-Ligated I(V) Reagents, Bi(N)-HVIs: Preparation, Stability, Structure, and Reactivity
Xiao, Xiao,Roth, Jessica M.,Greenwood, Nathaniel S.,Velopolcek, Maria K.,Aguirre, Jordan,Jalali, Mona,Ariafard, Alireza,Wengryniuk, Sarah E.
, p. 6566 - 6576 (2021/05/06)
Hypervalent iodine(V) reagents are a powerful class of organic oxidants. While the use of I(V) compounds Dess-Martin periodinane and IBX is widespread, this reagent class has long been plagued by issues of solubility and stability. Extensive effort has been made for derivatizing these scaffolds to modulate reactivity and physical properties but considerable room for innovation still exists. Herein, we describe the preparation, thermal stability, optimized geometries, and synthetic utility of an emerging class of I(V) reagents, Bi(N)-HVIs, possessing datively bound bidentate nitrogen ligands on the iodine center. Bi(N)-HVIs display favorable safety profiles, improved solubility, and comparable to superior oxidative reactivity relative to common I(V) reagents. The highly modular synthesis and in situ generation of Bi(N)-HVIs provides a novel and convenient screening platform for I(V) reagent and reaction development.
Photocontrolled Cobalt Catalysis for Selective Hydroboration of α,β-Unsaturated Ketones
Beltran, Frédéric,Bergamaschi, Enrico,Funes-Ardoiz, Ignacio,Teskey, Christopher J.
supporting information, p. 21176 - 21182 (2020/09/17)
Selectivity between 1,2 and 1,4 addition of a nucleophile to an α,β-unsaturated carbonyl compound has classically been modified by the addition of stoichiometric additives to the substrate or reagent to increase their “hard” or “soft” character. Here, we demonstrate a conceptually distinct approach that instead relies on controlling the coordination sphere of a catalyst with visible light. In this way, we bias the reaction down two divergent pathways, giving contrasting products in the catalytic hydroboration of α,β-unsaturated ketones. This includes direct access to previously elusive cyclic enolborates, via 1,4-selective hydroboration, providing a straightforward and stereoselective route to rare syn-aldol products in one-pot. DFT calculations and mechanistic experiments confirm two different mechanisms are operative, underpinning this unusual photocontrolled selectivity switch.
CeO2-Supported Pd(II)-on-Au Nanoparticle Catalyst for Aerobic Selective α,β-Desaturation of Carbonyl Compounds Applicable to Cyclohexanones
Jin, Xiongjie,Mizuno, Noritaka,Takei, Daisuke,Yabe, Tomohiro,Yamaguchi, Kazuya,Yatabe, Takafumi
, p. 5057 - 5063 (2020/05/27)
Direct selective desaturation of carbonyl compounds to synthesize α,β-unsaturated carbonyl compounds represents an environmentally benign alternative to classical stepwise procedures. In this study, we designed an ideal CeO2-supported Pd(II)-on-Au nanoparticle catalyst (Pd/Au/CeO2) and successfully achieved heterogeneously catalyzed selective desaturation of cyclohexanones to cyclohexenones using O2 in air as the oxidant. Besides cyclohexenones, various bioactive enones can also be synthesized from the corresponding saturated ketones under open air conditions in the presence of Pd/Au/CeO2. Preliminary mechanistic studies revealed that α-C-H bond cleavage in the substrates is the turnover-limiting step of this desaturation reaction.
2-Iodoxybenzoic acid ditriflate: The most powerful hypervalent iodine(v) oxidant
Yusubov, Mekhman S.,Soldatova, Natalia S.,Postnikov, Pavel S.,Valiev, Rashid R.,Yoshimura, Akira,Wirth, Thomas,Nemykin, Victor N.,Zhdankin, Viktor V.
supporting information, p. 7760 - 7763 (2019/07/12)
A ditriflate derivative of 2-iodoxybenzoic acid (IBX) was prepared by the reaction of IBX with trifluoromethanesulfonic acid and characterized by single crystal X-ray crystallography. IBX-ditriflate is the most powerful oxidant in a series of structurally similar IBX derivatives which is best illustrated by its ability to readily oxidize hydrocarbons and the oxidation resistant polyfluoroalcohols.
Enantioselective Total Syntheses of Pallambins A–D
Zhang, Xiwu,Cai, Xinxian,Huang, Bin,Guo, Lei,Gao, Zhongrun,Jia, Yanxing
, p. 13380 - 13384 (2019/08/16)
The first enantioselective total syntheses of (?)-pallambins A–D have been achieved in 15 or 16 steps from a known chiral cyclohexenone. Salient features of the syntheses include a palladium-catalyzed oxidative cyclization to assemble the [3.2.1]bicyclic moiety, an Eschenmoser–Claisen rearrangement/lactone formation sequence to construct the C ring, an intramolecular Wittig reaction to form the D ring, and individual transformations of pallambins C and D to generate pallambins A and B. The described synthesis avoids protecting-group manipulations through the design of highly chemo- and stereoselective transformations. During the course of this work, a palladium-catalyzed method for the dehydrobromination of α-bromoketones was developed, and the scope of this transformation was also investigated.
Synthesis of Cyclic Enones by Allyl-Palladium-Catalyzed α,β-Dehydrogenation
Huang, David,Zhao, Yizhou,Newhouse, Timothy R.
supporting information, p. 684 - 687 (2018/02/09)
The use of allyl-palladium catalysis for the one-step α,β-dehydrogenation of ketones via their zinc enolates is reported. The optimized protocol utilizes commercially available Zn(TMP)2 as base and diethyl allyl phosphate as oxidant. Notably, this transformation operates under salt-free conditions and tolerates a diverse scope of cycloalkanones.
Non-redox metal ions promoted oxidative dehydrogenation of saturated C[sbnd]C bond by simple Pd(OAc)2 catalyst
Lou, Chenlin,Qin, Shuhao,Zhang, Sicheng,Lv, Zhanao,Senan, Ahmed M.,Chen, Zhuqi,Yin, Guochuan
, p. 5 - 9 (2016/11/22)
Adding non-redox metal ions to simple Pd(OAc)2 catalyst can remarkably promote oxidative dehydrogenation of saturated C[sbnd]C bond, and the activity improvement is Lewis acidity strength dependent. Through UV–vis and NMR characterizations of the catalyst, it was proposed that in-situ generated heteronuclear Pd(II)/Zn(II) dimer is the key active species for dehydrogenation.
Allyl-Palladium-Catalyzed Ketone Dehydrogenation Enables Telescoping with Enone α,β-Vicinal Difunctionalization
Chen, Yifeng,Huang, David,Zhao, Yizhou,Newhouse, Timothy R.
supporting information, p. 8258 - 8262 (2017/06/30)
The telescoping of allyl-palladium catalyzed ketone dehydrogenation with organocuprate conjugate addition chemistry allows for the introduction of aryl, heteroaryl, vinyl, acyl, methyl, and other functionalized alkyl groups chemoselectively to a wide variety of unactivated ketone compounds via their enone counterparts. The compatibility of the dehydrogenation conditions additionally allows for efficient trapping of the intermediate enolate with various electrophiles. The utility of this approach is demonstrated by comparison to several previously reported multistep sequences.
Palladium-catalyzed saegusa-ito oxidation: Synthesis of α,β-Unsaturated carbonyl compounds from trimethylsilyl enol ethers
Lu, Yingdong,Nguyen, Pierre Long,Levaray, Nicolas,Lebel, Heleine
, p. 776 - 779 (2013/02/25)
Palladium-catalyzed Saegusa-Ito oxidation of trimethylsilyl enol ethers is possible using Oxone as a stoichiometric oxidant and sodium hydrogen phosphate as a buffer. Cyclic and acyclic enones as well as α,β-unsaturated aldehydes are obtained in good to excellent yields.
