- Selective Aerobic Oxygenation of Tertiary Allylic Alcohols with Molecular Oxygen
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Aerobic epoxidation of tertiary allylic alcohols remains a significant challenge. Reported here is an efficient and highly chemoselective copper-catalyzed epoxidation and semipinacol rearrangement reaction of tertiary allylic alcohols with molecular oxygen. The solvent 1,4-dioxane activates dioxygen, thereby precluding the addition of a sacrificial reductant.
- Zhu, Bencong,Shen, Tao,Huang, Xiaoqiang,Zhu, Yuchao,Song, Song,Jiao, Ning
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p. 11028 - 11032
(2019/07/08)
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- Why is cis/trans stereoinversion with Li+(THF)4 migration across the phenyl ring of α-lithiostyrene accelerated by two ortho-methyl groups?
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Common wisdom might anticipate that two methyl groups placed on a molecular migration route should act as an impediment. However, the “conducted tour” migration of Li+(THF)4 across the aryl ring (“π-route”) during the cis/trans stereoinversion of α-arylvinyllithiums had been found to occur with practically equal velocities in the presence of either one or two ortho-alkyl substituents. We now report that the omission of both ortho-methyl groups retards the stereoinversion process. In order to arrive at an answer to the title question, we investigate the aggregation equilibria and microsolvation states of ortho, ortho′-unsubstituted α-lithiostyrenes by means of approved secondary NMR criteria. Beyond such necessary knowledge about the ground-state properties, we provide kinetic evidence showing that the retarded cis/trans stereoinversion of α-lithiostyrene proceeds by the pseudomonomolecular, ionic mechanism with Li+(THF)4 migration.
- Knorr, Rudolf,Lattke, Ernst,Ruhdorfer, Jakob,Ferchland, Kathrin,von Roman, Ulrich
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p. 1621 - 1631
(2018/02/28)
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- N-BuLi/LiCH2CN-mediated one-carbon homologation of aryl epoxides into conjugated allyl alcohols
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A series of styrene oxides in the presence of a 1:1 mixture of n-butyllithium (n-BuLi) and lithioacetonitrile (LiCH2CN) in THF are converted into one-carbon homologated allyl alcohols in an unusual regioselective manner.
- Tomioka, Takashi,Sankranti, Rambabu,Yamada, Tsuyoshi,Clark, Courtney
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supporting information
p. 5099 - 5101
(2013/10/22)
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- Microwave-assisted one-pot hydrostannylation/Stille couplings.
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In a fraction of the time required by conventional methods, microwave-accelerated one-pot hydrostannylation/Stille coupling allows 1-alkynes to be efficiently transformed into 1,3-dienes or styrenes.
- Maleczka Jr.,Lavis,Clark,Gallagher
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p. 3655 - 3658
(2007/10/03)
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- A novel palladium-catalyzed asymmetric cyclocarbonylation of allylic alcohols to γ-butyrolactones
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A catalyst system based on [Pd2(dba)3]·CHCl3/(-)-BPPM has been found to effect asymmetric cyclocarbonylation of certain prochiral allylic alcohols to produce good yields of optically enriched γ-butyrolactones. The reaction
- Yu, Wing-Yiu,Bensimon, Corinne,Alper, Howard
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p. 417 - 423
(2007/10/03)
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- The reaction of trialkylstannylmethyllithium with α,β-epoxy ketones and α-chloro ketones
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The reactions of trialkylstannylmethyllithium with α,β-epoxy ketones afforded mainly cyclopropanols, while α-chloro ketones afforded allyl alcohols and/or cyclopropanols, in varying amounts depending upon the molar ratio of the reagent to the substrate.
- Sato, Tadashi,Kikuchi, Toshihiro,Tsujita, Hiroshi,Kaetsu, Atsushi,Sootome, Norio,Nishida, Ken-Ichiro,Tachibana, Kazutaka,Murayama, Eigoro
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p. 3281 - 3304
(2007/10/02)
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- MECHANISTIC STUDY ON THE PHOTO-OXIDATION OF α-DIKETONES. INTERACTION OF TRIPLET α-DIKETONES WITH OXYGEN
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The mechanism for photo-oxidation of α-diketones in the presence of olefins has been studied, focusing on the interaction of triplet diketones with O2.Two types of reactions occur competitively.One is the formation of 1O2 by energy transfer to O2 and the other is the addition of O2 to triplet diketone, which yields acylperoxy radicals leading to the radical epoxidation of olefins.Ratios of the two reactions were determined from the yields of 1O2 products and epoxides.For most diketones, quantum yields for 1O2 formation were considerably high, in the range 0.3-0.8; but the yields for epoxides were in a wider range of 0.001-0.5.While the ratios of 1O2 formation and O2 addition to triplet diketones ranged from 29:71 for biacetyl to 1:99 for mesitil, the ratios remained constant by changing solvents or temperature.The latter O2 addition reaction decreased in the order of MeCOCOMe > PhCOCOMe > PhCOCOPh but the effect of m- and p-substituents on benzils was not significant, indicating the addition of O2 as a neutral biradical.In exceptional cases, the O2 addition was not effective for sterically inaccessible mesitil and some cyclic α-diketones.The mechanism of 1O2 formation was discussed in comparison to other carbonyl compounds.
- Sawaki, Yasuhiko
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p. 2199 - 2206
(2007/10/02)
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- Substitution Reactions of Secondary Halides and Epoxides with Higher Order, Mixed Organocuprates, R2Cu(CN)Li2: Synthetic, Stereochemical, and Mechanistic Aspects
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Higher order cuprates, represented by the general formula R2Cu(CN)Li2, are readily prepared from copper cyanide and 2 equiv of an organolithium.These novel reagents react readily and efficiently with secondary unactivated iodides and bromides affording products of substitution.Likewise, mono-, di-, and trisubstituted epoxides undergo ring opening leading to the corresponding alcohols in excellent yields.The effects of solvent, temperature, gegenion, and variations in ligands are discussed.Replacement of the second equivalent of RLi by CH3Li strongly encouragestransfer of R over CH3 in R(CH3)Cu(CN)Li2 with halides.Use of PhLi as RRLi in place of one RTLi (i.e.RT(Ph)Cu(CN)Li2) is suggested for oxirane cleavage.The stereochemical implications associated with both couplings are also addressed.
- Lipshutz, Bruce H.,Wilhelm, Robert S.,Kozlowski, Joseph A.,Parker, David
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p. 3928 - 3938
(2007/10/02)
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