- Reductive Etherification via Anion-Binding Catalysis
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Reductive condensations of alcohols with aldehydes/ketones to generate ethers are catalyzed by a readily accessible thiourea organocatalyst that operates in combination with HCl. 1,1,3,3-tetramethyldisiloxane serves as a convenient reducing reagent. This strategy is applicable to challenging substrate combinations and exhibits functional group tolerance. Competing reductive homocoupling of the carbonyl component is suppressed.
- Zhao, Chenfei,Sojdak, Christopher A.,Myint, Wazo,Seidel, Daniel
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supporting information
p. 10224 - 10227
(2017/08/10)
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- Acid- and isobutylene-free synthesis of t-butyl ethers by in situ formation of 2-t-butoxy-1-methylpyridinium triflate
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The title reagent is formed in situ by alkylation of 2-t-butoxypyrine. The subsequent addition of an alcohol substrate leads to the formation of t-butyl ethers without the need for isobutylene gas or acid activators.
- Salvati, Anna E.,Hubley, Christian T.,Albiniak, Philip A.
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supporting information
p. 7133 - 7135
(2015/01/08)
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- Direct conversion of tosylhydrazones to tert-butyl ethers under Bamford-Stevens reaction conditions
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A new method for the preparation of tert-butyl ethers is described starting from aryl aldehyde and ketone tosylhydrazones under Bamford-Stevens reaction conditions (t-BuOK/t-BuOH).
- Chandrasekhar,Rajaiah,Chandraiah,Narsimha Swamy
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p. 1779 - 1780
(2007/10/03)
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- Oxidation of benzylsilanes and benzyltins by oxovanadium(V) compound and molecular oxygen
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Benzylsilane and benzyltin compounds were oxidized by oxovanadium(V) compound under an oxygen atmosphere to afford the corresponding aromatic aldehydes (ketones) and/or carboxylic acids. In the reaction of benzyltins, oxovanadium(V) compound can be reduce
- Hirao, Toshikazu,Morimoto, Chihiro,Takada, Takashi,Sakurai, Hidehiro
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p. 5073 - 5079
(2007/10/03)
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- Photochemistry of phosphate esters: An efficient method for the generation of electrophiles
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The photochemical cleavage of benzyl diethyl phosphates, 1a-g, has been examined in tert-butyl alcohol, which produces the corresponding benzyl tert-butyl ether as the major solvolysis product upon direct irradiation. The multiplicity of the reactive excited state has been established as the singlet state. Evidence favoring an intermediate benzyl cation-phosphate ion pair formed from photofragmentation includes oxygen-18 scrambling, racemization of chiral benzyl phosphates, and substituent effects on the rate of reaction. The existence of an electrophilic intermediate is further supported by a linear free energy relationship for the rate of disappearance of 1, kdis, with Hammett σ, which gave a ρ value of -0.90 and for the rate of appearance of 2, kapp, a Hammett ρ value of -0.97. Possible mechanisms including an electron transfer either before or after homolysis or simple heterolysis of the ester bond are evaluated.
- Givens, Richard S.,Matuszewski, Bogdan,Athey, Phillip S.,Robert Stoner
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p. 6016 - 6021
(2007/10/02)
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- REACTIVITY OF 3,6-DIMETHOXY-3,6-DIMETHYLCYCLOHEXA-1,4-DIENE: NUCLEAR VERSUS BENZYLIC NUCLEOPHILIC SUBSTITUTION
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The treatment of cis/trans-3,6-dimethoxy-3,6-dimethylcyclohexa-1,4-diene (ca. 1/1 mixture; easily prepared electrochemically in multigram scale from p-xylene) under acidic conditions (acetic, trifluoroacetic, sulfuric, or a Lewis acid) yields almost exclusively 2-methoxy-1,4-dimethylbenzene 4, through a trasposition reaction.The use of aqueous hydrochloric or hydrofluoric acid gives 2,5-dimethylphenol 12, and with hydrogen chloride a mixture of 2- and α-chloro-p-xylene (13, 14) is isolated.Different oxygen-, nitrogen-, and sulfur-containing nucleophiles (alcohols,thiols, or hydrazoic acid) react with 3 under acid catalysis giving the corresponding products resulting from a nuclear or/ and benzylic substitution on p-xylene (15 - 20).The reaction of compound 3 with organolithium reagents affords exclusively benzylic products 21 in a regiospecific manner.In all cases the mixtures of isomers are separated by column chromatography.The lithiation of compound 3 with lithium powder or lithium naphthalenide fails, giving p-xylene.A probable mechanism is proposed for the studied reactions.
- Alonso, Francisco,Barba, Isidoro,Yus, Miguel
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p. 2069 - 2080
(2007/10/02)
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- Generation of Bicycloheptatrienes
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Derivatives of bicycloheptatriene have been generated in solution by the base-induced dehydrochlorination of gem-dichlorocyclopropanes.Reaction of 7,7-dichlorodibenzobicycloheptane with potassium tert-butoxide in tetrahydrofuran at 0 deg C gives mainly products derived from solvent incorporation by carbene insertion.Evidence that the carbene results from rearrangement of the bicycloheptatriene derives from the successful interception of the bicycloheptatriene with nucleophile (MeS-). endo-7-Chlorodibenzobicycloheptane failed to reactwith potassium tert-butoxide in tetrahydrofuran.Generation of benzobicycloheptatrienes was also accomplished via the base-induced dehydrochlorination of gem-dichlorocyclopropanes. 1-Methylbenzobicycloheptatriene gives products derived from multiple carbene-carbene rearrangements.In contrast, nonannelated methylbicycloheptatrienes generated by the dehydrochlorination route give only carbene-derived products resulting from the initially produced bicycloheptatriene.
- Billups, W. E.,Reed, Larry E.,Casserly, Edward W.,Lin, L. P.
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p. 1326 - 1333
(2007/10/02)
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