- Site-Specific Alkene Hydromethylation via Protonolysis of Titanacyclobutanes
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Methyl groups are ubiquitous in biologically active molecules. Thus, new tactics to introduce this alkyl fragment into polyfunctional structures are of significant interest. With this goal in mind, a direct method for the Markovnikov hydromethylation of alkenes is reported. This method exploits the degenerate metathesis reaction between the titanium methylidene unveiled from Cp2Ti(μ-Cl)(μ-CH2)AlMe2 (Tebbe's reagent) and unactivated alkenes. Protonolysis of the resulting titanacyclobutanes in situ effects hydromethylation in a chemo-, regio-, and site-selective manner. The broad utility of this method is demonstrated across a series of mono- and di-substituted alkenes containing pendant alcohols, ethers, amides, carbamates, and basic amines.
- Bartfield, Noah M.,Frederich, James H.,Law, James A.
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supporting information
p. 14360 - 14364
(2021/05/27)
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- 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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- Tandem ring-closing metathesis/transfer hydrogenation: Practical chemoselective hydrogenation of alkenes
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An operationally simple chemoselective transfer hydrogenation of alkenes using ruthenium metathesis catalysts is presented. Of great practicality, the transfer hydrogenation reagents can be added directly to a metathesis reaction and effect hydrogenation of the product alkene in a single pot at ambient temperature without the need to seal the vessel to prevent hydrogen gas escape. The reduction is applicable to a range of alkenes and can be performed in the presence of aryl halides and benzyl groups, a notable weakness of Pd-catalyzed hydrogenations. Scope and mechanistic considerations are presented.
- Connolly, Timothy,Wang, Zhongyu,Walker, Michael A.,McDonald, Ivar M.,Peese, Kevin M.
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p. 4444 - 4447
(2015/01/09)
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- Action of Lewis Acids on Aromatic Acetals
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Acetals of the type X.C6H4CH(OR)2, where R = Et, n-Bu and isoamyl, and X = H and CH3, react with antimony perchloride and ferric chloride in anhydrous 1,2-dichloroethane to give benzyl alkyl ether, alkyl benzoate, benzyl ester, α,β-unsaturated aldehyde, benzaldehyde and a small quantity of benzyl alcohol. p-Nitrobenzaldehyde di-n-butyl acetal gave only p-nitrobenzaldehyde and a trace of p-nitrobenzyl alcohol.The mechanism of the formation of benzyl alkyl ether is explained by a hydride ion transfer and that of α,β-unsaturated aldehyde by an aldol type of condensation.The aliphatic and aromatic aldehydes produced in the reaction could undergo Tischenko reaction in the presence of antimony or iron alkoxides to give the esters.
- Alphonse, I.,Arulraj, S. J.
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p. 820 - 822
(2007/10/02)
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- Action of Boron Trifluoride on Aromatic Acetals
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Acetals of the type X-C6H4CH(OR)2 (where R = Et, n-Bu and isoamyl and X = H, CH3) react with boron trifluoride in anhyd. 1,2-dichloroethane to give benzyl alkyl ethers, α,β-unsaturated aldehydes and benzaldehyde.However, p-nitrobenzaldehyde di-n-butyl acetal gives only p-nitrobenzaldehyde.The formation of benzyl alkyl ethers is explained by a hydride ion transfer mechanism and that of α,β-unsaturated aldehyde by an aldol-type of condensation.
- Alphonse, I.,Arulraj, S. J.
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p. 199 - 200
(2007/10/02)
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- Rearrangement of Aromatic Acetals Over Solid Acid Catalysts
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The reactions of aromatic acetals (1a-6a) catalysed by aluminium phosphate (AP) yield the corresponding esters (b), ethers (c) and the parent aldehydes (d).Similar reactions over aluminium sulphate (AS) give only esters (b) and the aldehydes (d).Probable mechanisms have been suggested for the reactions.The catalysts have been characterized by various studies.The specific poisoning of the catalysts have been done with NH3 and CO2 and the product formation on the poisoned catalyst provides support to the suggested mechanisms.
- Xavier, N.,Arulraj, S. J.
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p. 519 - 522
(2007/10/02)
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