- Synthesis of Oxa-Bridged Medium-Sized Carbocyclic Rings via Prins Cyclization
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Herein, we report a new method for the synthesis of oxa-bridged carbocyclic units based on intramolecular Prins reaction of dioxinones. Our new synthetic approach is flexible and practical and has been successfully applied to the preparation of highly fun
- Wang, Min-Shou,Wang, Zheng,Chen, Wen,Yang, Xiaodong,Zhang, Hongbin
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- Nickel-catalyzed remote hydrosilylation of unconjugated enones with bulky triphenylsilane
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Herein we describe a nickel-catalyzed remote hydrosilylation of unconjugated enones with bulky triphenylsilane. A range ofZ-silyl enol ethers are obtained as major isomers due to the process of nickel triggered alkene isomerization. Notably, some specific
- Chen, Xue,Jin, Hongwei,Liu, Yunkui,Wang, Zhen,Zhou, Bingwei,Zhou, Jinyong
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p. 8021 - 8024
(2021/10/04)
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- Light-Driven Carbene Catalysis for the Synthesis of Aliphatic and α-Amino Ketones
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Single-electron N-heterocyclic carbene (NHC) catalysis has gained attention recently for the synthesis of C?C bonds. Guided by density functional theory and mechanistic analyses, we report the light-driven synthesis of aliphatic and α-amino ketones using single-electron NHC operators. Computational and experimental results reveal that the reactivity of the key radical intermediate is substrate-dependent and can be modulated through steric and electronic parameters of the NHC. Catalyst potential is harnessed in the visible-light driven generation of an acyl azolium radical species that undergoes selective coupling with various radical partners to afford diverse ketone products. This methodology is showcased in the direct late-stage functionalization of amino acids and pharmaceutical compounds, highlighting the utility of single-electron NHC operators.
- Bay, Anna V.,Cheong, Paul Ha-Yeon,Farah, Abdikani Omar,Fitzpatrick, Keegan P.,González-Montiel, Gisela A.,Scheidt, Karl A.
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p. 17925 - 17931
(2021/07/17)
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- A New Route to Phenols: Palladium-Catalyzed Cyclization and Oxidation of γ,δ-Unsaturated Ketones
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We report a new strategy for the synthesis of phenols from acyclic unsaturated ketones in one pot. The reaction proceeds by palladium-catalyzed carbopalladation of an alkene with the enol form of the tethered ketone, generating a substituted cyclohexanone. Upon introduction of a terminal oxidant a palladium-catalyzed oxidation ensues to give the desired phenol. This approach allows the programming of phenol substituents on the acyclic substrate and therefore circumvents the limitations inherent in traditional syntheses of phenols.
- Samadi, Sadaf,Orellana, Arturo
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p. 2472 - 2475
(2016/08/25)
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- Copper(II) carboxylate promoted intramolecular diamination of terminal alkenes: Improved reaction conditions and expanded substrate scope
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The copper(II) carboxylate promoted diamination reaction has been improved by the use of the organic soluble copper(II) neodecanoate [Cu(ND)2]. Cu(ND)2 allowed the less-polar solvent dichloroethane (DCE) to be used, and as a consequence, decomposition of less-reactive substrates could be avoided. High diastereoselectivity was observed in the synthesis of 2,5-disubstituted pyrrolidines. Ureas, bis(anllines), and α-amido pyrroles derived from 2-allylaniline could also participate in the diamination reaction.
- Zabawa, Thomas P.,Chemler, Sherry R.
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p. 2035 - 2038
(2008/02/02)
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- Multicomponent reactions involving 2-methyleneaziridines: Rapid synthesis of 1,3-disubstituted propanones
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Ring opening of 1-alkyl-2-methyleneaziridines 1 or 2 is accomplished with organocopper reagents (R2CuLi or RMgX/CuI) in the presence of boron trifluoride diethyl etherate giving 1-substituted propan-2-ones 3-9 in 42-88% yield. Ring opening with RMgC1/CuI in the absence of the Lewis acid allows further alkylation of the metalloenamine (metalated imine) intermediate in a regiocontrolled manner. The sequential formation of two new intermolecular carbon-carbon bonds in this reaction provides a rapid entry into a variety of 1,3-disubstituted propan-2-ones, including 11 and 14-23. The scope and mechanism of this multicomponent reaction (MCR) has been assessed. It is established that this MCR tolerates alkyl, aryl, and benzyiic Grignard reagents and a wide range of electrophiles, including alkyl iodides, bromides, and tosylates, as well as epoxides and aldehydes. In addition, gem-dimethyl substitution on the exocyclic double bond of the 2-methyleneaziridine is tolerated. This MCR has been applied to the one-pot synthesis of (Z)-6-heneicosen11-one, 25, an important sex attractant of the Tussock moth. Using 3-deuterio-1-(1-phenylethyl)2-methyleneaziridine, 26, we determined that this MCR occurs predominantly by direct ring opening at the sp3-hybridized aziridine carbon atom (C-3).
- Hayes, Jerome F.,Shipman, Michael,Twin, Heather
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p. 935 - 942
(2007/10/03)
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- Radical addition to carbenoids. Chain reactions of α-diazo carbonyl compounds with triorganotin hydrides, tris(trimethylsilyl)silane and allyltributylstannane
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α-Diazo ketones RC(O)CH=N2 react with tributyltin hydride at 60°C in benzene to give the corresponding α-stannyl ketones RC(O)CH2SnBu3, which exist in equilibrium with the stannyl enol ether tautomers R(Bu3SnO)C=CH2. The reactions are initiated by di-tert-butyl hyponitrite and follow a free-radical chain mechanism. Triphenyltin hydride and tris(trimethylsilyl)silane [(TMS)3SiH] react similarly, the latter to yield the α-silyl ketone RC(O)CH2Si(TMS)3 which does not isomerise to the more stable silyl enol ether R[(TMS)3SiO]C=CH2 under the reaction conditions. This result indicates that TMS3Si. reacts at the α-carbon atom of the α-diazo ketone to give R(CO)CHSiTMS3, probably via an initial diazenyl radical adduct; triorganotin radicals are assumed to react in the same way. When the group R in the α-diazo ketone is but-3-enyl, the intermediate α-metalloalkyl radical undergoes 5-exo-cyclisation. Allyltributylstannane reacts with α-diazo ketones and with ethyl α-diazoacetate in refluxing benzene, in the presence of 2,2′-azo(2-methylpropionitrile) as initiator, to give butenyl ketones RC(O)CH2CH2CH=CH2 and ethyl pent-4-enoate, respectively, after a hydrolytic work-up.
- Dang, Hai-Shan,Roberts, Brian P.
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p. 769 - 775
(2007/10/03)
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- Formation and Reactions of 1-Phenyl-2-propanone Dianion and Related Systems with Electrophilic Reagents
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1-Phenyl-2-propanone, 1,1-diphenyl-2-propanone, and 1-(4-methoxyphenyl)-2-propanone were converted to their dicarbanions 3, 4, and 31, respectively, and their reactions with a number of electrophilic reagents were examined.All three dianions gave a mixture of C-1 and C-3 alkylation products when treated with alkyl halides of higher reactivity, while only C-1 alkylations occurred when alkyl halides of lower reactivity were used.It was also found that the 1,1-diphenyl-2-propanone and the 1-(4-methoxyphenyl)-2-propanone dianions 4 and 31 gave a higher ratio of C-1/C-3 alkylation products than the 1-phenyl-2-propanone dianion 3.When dianion 3 was reacted with p-anisaldehyde and a number of protonating agents, electrophilic attack occurred exclusively at the C-3 position.The trends observed are analyzed, and mechanisms are proposed to account for the results obtained.
- Trimitsis, G. B.,Hinkley, J. M.,TenBrink, R.,Faburada, A. L.,Anderson, R.,et al.
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p. 2957 - 2962
(2007/10/02)
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- Silicon-Assisted Ring Opening of Cyclopropyl Ketones with Boron Trifluoride-Acetic Acid Complex
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2-(Trimethylsilylmethyl)cyclopropyl ketones were smoothly cleaved with boron trifluoride-acetic acid complex under mild reaction conditions with the assistance of the trimethylsilyl group to give γ,δ-enones in good yields.The major effect of the trimethylsilyl group in the ring opening of the cyclopropyl ketones was unambiguously confirmed in the dicyclopropyl ketone 15: one of its two cyclopropyl rings, which has a trimethylsilylmethyl group, was selectively cleaved.Furthermore, the reaction was applied to the formal total synthesis of cis-jasmone.Keywords - ring opening of cyclopropyl ketone; trimethylsilyl group; γ,δ-enone; cis-jasmone; allylsilane; boron trifluoride-acetic acid
- Ochiai, Masahito,Sumi, Kenzo,Fujita, Eiichi
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p. 3931 - 3938
(2007/10/02)
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- SIMPLE PREPARATION OF 1-BROMO-1-TRIMETHYLSILYL-(Z),4-PENTADIENE AND ITS USE AS 4-PENTENOYL ANION EQUIVALENT
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The title compound is easily obtained by palladium(II)-catalyzed bromoallylation of ethynyltrimethylsilane and can serve as 4-pentenoyl anion equivalent which is a valuable synthetic grouping.
- Yamaguchi, R.,Kawasaki, H.,Kawanisi, M.
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p. 1027 - 1038
(2007/10/02)
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- RING OPENING OF CYCLOPROPYL KETONES ASSISTED BY THE TRIMETHYLSILYL GROUP
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Cyclopropyl ketones 2 were smoothly cleaved with boron trifluoride-acetic acid under mild reaction conditions by the assistance of trimethylsilyl group to give γ,δ-enones in good yields and the reaction was applied to the formal total synthesis of cis-jasmone.
- Ochiai, Masahito,Sumi, Kenzo,Fujita, Eiichi
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