- Umpolung Strategy for Arene C?H Etherification Leading to Functionalized Chromanes Enabled by I(III) N-Ligated Hypervalent Iodine Reagents
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The direct formation of aryl C?O bonds via the intramolecular dehydrogenative coupling of a C?H bond and a pendant alcohol represents a powerful synthetic transformation. Herein, we report a method for intramolecular arene C?H etherification via an umpoled alcohol cyclization mediated by an I(III) N-HVI reagent. This approach provides access to functionalized chromane scaffolds from primary, secondary and tertiary alcohols via a cascade cyclization-iodonium salt formation, the latter providing a versatile functional handle for downstream derivatization. Computational studies support initial formation of an umpoled O-intermediate via I(III) ligand exchange, followed by competitive direct and spirocyclization/1,2-shift pathways. (Figure presented.).
- Mikhael, Myriam,Guo, Wentao,Tantillo, Dean J.,Wengryniuk, Sarah E.
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supporting information
p. 4867 - 4875
(2021/09/14)
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- Alkyl Ethers as Traceless Hydride Donors in Br?nsted Acid Catalyzed Intramolecular Hydrogen Atom Transfer
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A new protocol for the deoxygenation of alcohols and the hydrogenation of alkenes under Br?nsted acid catalysis has been developed. The method is based on the use of either a benzyl or isopropyl ether as a traceless hydrogen-atom donor, and involves an intramolecular hydride transfer as a key step, which is achieved in a regio- and stereoselective manner.
- Gandamana, Dhika Aditya,Wang, Bin,Tejo, Ciputra,Bolte, Benoit,Gagosz, Fabien,Chiba, Shunsuke
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supporting information
p. 6181 - 6185
(2018/05/03)
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- Organolanthanide-Catalyzed Cyclization/Boration of 1,5- and 1,6-Dienes
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(Matrix Presented) 1,5- and 1,6-Dienes undergo a cyclization/boration reaction in the presence of a catalytic amount of Cp*2Sm·THF. The resulting organoboranes can be oxidized to the corresponding primary cyclic alcohols using standard conditions.
- Molander, Gary A.,Pfeiffer, Dirk
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p. 361 - 363
(2007/10/03)
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- Design, synthesis, and application of a C2 symmetric chiral ligand for enantioselective conjugate addition of organolithium to α,β-unsaturated aldimine
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A C2 symmetric chiral diether ligand, (1R,2R)-1,2-dimethoxy-1,2- diphenylethane, was designed and synthesized on the basis of the concept of an asymmetric oxygen atom. Mediated by the chiral diether, high enantioselectivities were achieved in conjugate addition of organolithiums to naphthaldehyde imine and cyclic and acyclic α,β-unsaturated aldimines. The absolute configuration of the product is predictable by the model.
- Shindo, Mitsuru,Koga, Kenji,Tomioka, Kiyoshi
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p. 9351 - 9357
(2007/10/03)
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- Auxiliary-directed peroxidation of 1,4-dienes
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The addition of singlet oxygen (1O2) to the proximal alkene of auxiliary-tethered 1,4-dienes and the addition of triplet oxygen 3O2) to the proximal position of the corresponding pentadienyl radicals both produce conjugated diene hydroperoxides in moderate to high diastereomeric excess. Negligible stereoselection is observed for additions of 1O2 to the distal alkene of Z,Z-heptadienes due to the lack of control of alkene conformation. Despite evidence for the intermediacy of highly constrained pentadienyl radicals, poor diastereoselection is also observed for distal addition of 3O2. The extent of olefin isomerization observed during radical oxygenations can be correlated with steric constraints on the intermediate pentadienyl and peroxyl radicals and may be relevant to literature reports of olefin isomerization during enzymatic oxygenations of unnatural fatty acids.
- Dussault, Patrick H.,Anderson, Todd A.,Hayden, Michael R.,Koeller, Kevin J.,Jason Niu
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p. 12381 - 12398
(2007/10/03)
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- Chemistry of Substituted (2-Butene-1,4-diyl)magnesium: A Facile Approach to Complex Carbocycles, Functionalized Ketones and Alcohols, and Silicon-Containing Heterocycles
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Highly reactive magnesium reacts with a wide variety of substituted 1,3-dienes to give the corresponding substituted (2-butene-1,4-diyl)magnesium complexes.Reactions of symmetrical (2-butene-1,4-diyl)magnesium with α,ω-alkylene dihalides form three-, four-, five-, and six-membered carbocycles.Significantly, the cyclizations are always stereospecific and completely regioselective.Depending on the initial 1,3-diene and specific electrophiles, uncyclized products can be obtained.Stepwise reactions of (2,3-dimethyl-2-butene-1,4-diyl)magnesium with two different electrophiles afford polyfunctionalized ketones with the generation of a quaternary center.Formal 1,2-additions can be effected in this manner.Substituted five- and six-membered cyclic ketones can also be synthesized in one step by this approach.Treatment of unsymmetrical (2-butene-1,4-diyl)magnesium complexes with triorganosilyl chlorides followed by cyclohexanone results in additions across a terminal double bond with high regioselectivity.Silicon-containing heterocycles or spiro compounds can be readily synthesized by using the bis-Grignard reagents.
- Rieke, Reuben D.,Xiong, Heping
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p. 3109 - 3118
(2007/10/02)
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- Chiral alcohol-induced diastereoselective conjugate addition and cyclization
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Conjugate addition of organocuprate reagents to α,β-unsaturated esters of chiral trans-cyclohexanediol proceeded diastereoselectively, and the intramolecular trapping of the generated enolate also afforded asymmetric cyclization products.
- Fang, Chenglin,Suemune, Hiroshi,Sakai, Kiyoshi
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p. 4751 - 4754
(2007/10/02)
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