ChemInform Abstract: Enantio- and Diastereoselective Access to Distant Stereocenters Embedded withinTetrahydroxanthenes: Utilizing ortho-Quinone Methides as Reactive Intermediates in Asymmetric Broensted Acid Catalysis.

ChemInform ◽  
2015 ◽  
Vol 46 (17) ◽  
pp. no-no
Author(s):  
Chien-Chi Hsiao ◽  
Hsuan-Hung Liao ◽  
Magnus Rueping
Keyword(s):  
Acid Catalysis ◽  
Reactive Intermediates ◽  
Quinone Methides

scholarly journals Reactive intermediates. Some chemistry of quinone methides

2000 ◽  
Vol 72 (12) ◽  
pp. 2299-2308 ◽  
Author(s):  
Y. Chiang ◽  
A. J. Kresge ◽  
Y. Zhu
Keyword(s):  
Acid Catalysis ◽  
Isotope Effects ◽  
Reactive Intermediates ◽  
Quinone Methide ◽  
Carbonyl Carbon Atom ◽  
Carbonyl Carbon ◽  
Quinone Methides ◽  
Rate Determining Step ◽  
Energy Relationships ◽  
Acid Catalyzed

Quinone methides were produced in aqueous solution by photochemical dehydration of o-hydroxybenzyl alcohols (o-HOC6H4CHROH; R = H, C6H5, 4-CH3OC6H4), and flash photolytic techniques were used to examine their rehydration back to starting substrate as well as their interaction with bromide and thiocyanate ions. These reactions are acid-catalyzed and show inverse isotope effects (kH+/kD+ < 1), indicating that they occur through preequilibrium protonation of the quinone methide on its carbonyl carbon atom followed by rate-determining capture of the benzyl carbocations so formed by H2O, Br-, or SCN-. With some quinone methides (R = C6H5 and 4-CH3OC6H4) this acid catalysis could be saturated, and analysis of the data obtained in the region of saturation for the example with R = 4-CH3OC6H4 produced both the equilibrium constant for the substrate protonation step and the rate constant for the rate-determining step. Energy relationships comparing the quinone methides with their benzyl alcohol precursors are derived.

[4+n] Annulation Reactions Using ortho-Halomethyl Anilines as Aza-ortho-Quinone Methide Precursors

Synthesis ◽  
2021 ◽  
Author(s):  
Xiao-Yu He ◽  
Yu-Hong Ma ◽  
Qing-Qing Yang ◽  
Wen-Jing Xiao
Keyword(s):  
Convenient Method ◽  
Reactive Intermediates ◽  
Quinone Methide ◽  
Synthetic Chemistry ◽  
Important Class ◽  
Quinone Methides ◽  
Aniline Derivatives

Aza-ortho-quinone methides are an important class of reactive intermediates, which have found broad applications in synthetic chemistry. Recently, 1,4-elimination of ortho-halomethyl aniline derivatives has emerged as a new powerful and convenient method for aza-ortho-quinone methide generation. This review will highlight their recent applications as aza-ortho-quinone methide precursors in annulation reactions to access various biologically important nitrogen-containing heterocycles. The general mechanisms are briefly discussed as well.

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