82638-98-0Relevant academic research and scientific papers
Site-Selective Alkoxylation of Benzylic C?H Bonds by Photoredox Catalysis
Lee, Byung Joo,DeGlopper, Kimberly S.,Yoon, Tehshik P.
supporting information, p. 197 - 202 (2019/11/26)
Methods that enable the direct C?H alkoxylation of complex organic molecules are significantly underdeveloped, particularly in comparison to analogous strategies for C?N and C?C bond formation. In particular, almost all methods for the incorporation of alcohols by C?H oxidation require the use of the alcohol component as a solvent or co-solvent. This condition limits the practical scope of these reactions to simple, inexpensive alcohols. Reported here is a photocatalytic protocol for the functionalization of benzylic C?H bonds with a wide range of oxygen nucleophiles. This strategy merges the photoredox activation of arenes with copper(II)-mediated oxidation of the resulting benzylic radicals, which enables the introduction of benzylic C?O bonds with high site selectivity, chemoselectivity, and functional-group tolerance using only two equivalents of the alcohol coupling partner. This method enables the late-stage introduction of complex alkoxy groups into bioactive molecules, providing a practical new tool with potential applications in synthesis and medicinal chemistry.
Reaction pathway and rate-determining step of the Schmidt rearrangement/fragmentation: A kinetic study
Akimoto, Ryo,Tokugawa, Takehiro,Yamamoto, Yutaro,Yamataka, Hiroshi
experimental part, p. 4073 - 4078 (2012/06/29)
The Schmidt rearrangement of substituted 3-phenyl-2-butanone with trimethylsilyl azide in 90% (v/v) aqueous TFA gave two types of product, fragmentation and rearrangement, the ratio of which depends on the substituent: more fragmentation for a more electron-donating substituent. Rate measurements by azotometry indicated the presence of an induction period, and the pseudo-first-order rate constants showed saturation kinetics with respect to the azide concentration. It was indicated that the reaction proceeds through pre-equilibrium in the formation of iminodiazonium (ID) ion and that the N 2 liberation from the ID ion is rate-determining. Under high azide concentration conditions, where the effective reactant is the ID ion, the reaction gave a linear Hammett plot with a value of -0.50. The observed substituent effects on the rate and the product selectivity imply that path bifurcation on the way from the rate-determining TS to the product states occurs, as suggested by previous molecular dynamics simulations, in a similar manner to the analogous Beckmann rearrangement/fragmentation reactions.
The (+/-)-1-(4-Methoxyphenyl)ethyl Ester as a Carboxyl Protecting Group
Bernatowicz, Michael S.,Chao, Hann-Guang,Matsueda, Gary R.
, p. 1651 - 1652 (2007/10/02)
Unhindered carboxylic acids were converted to their (+/-)-1-(4-methoxyphenyl)ethyl (MPe) esters in good yields by condensation with (+/-)-1-(4-methoxyphenyl)ethanol under mild conditions.The Mpe esters were rapidly and quantitatively cleavable by either 1percent TFA in CH2Cl2 or 10percent DCA in CH2Cl2, conditions which leave Boc, t-butyl ester and either intact.An Mpe ester was removed by hydrogenolysis much more slowsly than the analogous benzyl ester.
GENERAL BASE CATALYSIS OF THE ADDITION OF HYDROXYLIC REAGENTS TO UNSTABLE CARBOCATIONS AND ITS DISAPPEARANCE.
Richard,Jencks
, p. 1396 - 1401 (2007/10/02)
General base catalysis of the addition of ROH is significant for 1-phenylethyl carbocations of moderate stability and is most important for weakly basic alcohols. The Bronsted slope for catalysis of the addition of trifluoroethanol to the 1-(4-methoxyphenyl)ethyl carbocation is beta equals 0. 08. The development of positive charge on the attacking alcohol decreases with decreasing stability of the carbocation. It is concluded that the observed catalysis involves hydrogen bonding and represents the transition region between fully concerted, coupled general acid-base catalysis and specific acid catalysis with solvation of the proton in the transition state.
Addition of Trifluoroacetic Acid to Substituted Styrenes
Allen, Annette D.,Rosenbaum, Murray,Seto, Nina O. L.,Tidwell, Thomas T.
, p. 4234 - 4239 (2007/10/02)
The rate of addition of CF3CO2H to a series of ring-substituted styrenes ArCH=CH2 with 100percent, 50percent, and 20percent solutions of the acid in CCl4 have been measured.The rate of addition of 100percent CF3CO2H to the isomeric 1-phenylpropenes and the rate of cis- to trans-stilbene isomerization by this acid are also reported.The rates are correlated with ?+ parameters of the substituents and with aqueous H2SO4-catalyzed hydrations of the same substrates.Deviations from the ?+ correlation occur with substituents capable of strong hydrogen bonding to the acidic solvents; these deviations are attributed to a decrease in substituent electron-donating ability caused by this interaction.All of the evidence supports a mechanism of rate-determining protonation on carbon (the AdE2 mechanism), with no detectable effects from ? complexation of the acids with the substrates.
