ChemInform Abstract: Formation of Carbon‐Carbon Bonds via Quinone Methide‐Initiated Cyclization Reactions.

Angle, Steven R.; Arnaiz, Damian O.; Boyce, J. P.; Frutos, Rogelio P.; Louie, Michael S.; Mattson‐Arnaiz, H. L.; Rainier, Jon D.; Turnbull, Kenneth; Yang, Weichun

doi:10.1002/chin.199516048

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“…The cycloaddition of an o-QM with an electron-rich alkene has been employed as a key step in total syntheses, some representative examples are carpanone (lo), hexahydrocannabinol (7), and thielocin A1 P (1 1). para-Quinone methides have also been used in synthesis, notably by Angle et al (12). In these systems, p-QMs were generated, via Ag,O oxidation of the corresponding p-substituted phenol, that subsequently react via (a) formal [3+2] cycloaddition with an alkene, to give indanes or (b) undergo intramolecular cyclization to give a variety of p-hydroxyphenyl-substituted ring systems.…”

Section: Introductionmentioning

confidence: 99%

1995 Merck Frosst Award Lecture Quinone methides: relevant intermediates in organic chemistry

Wan¹,

Barker²,

Diao³

et al. 1996

Can. J. Chem.

151

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ortho and para-Quinone methides (2-methylene-3,5-cyclohexadien-I-one and 4-methylene-2,5-cyclohexadien-1-one, respectively) are intermediates in a variety of important chemical systems. In particular, o-quinone methides are useful in synthesis for the construction of chroman ring systems. A brief account of the relevance of quinone methide chemistry will be provided. This is followed by a review of recent studies from our laboratory on efficient methods for the photogeneration of quinone methides, concentrating on the use of hydroxy-substituted benzyl alcohols in aqueous media. It is shown that this method is general since it provides access too-, 171-, andp-quinone methide isomers. When appropriately substituted, all of these quinone methide isomers have been spectroscopically characterized by laser flash photolysis, making this technique the one of choice for studying the dynamics of these reactive intermediates. The mechanism of photochemical generation from hydroxybenzyl alcohols and extensions of the reaction to photogeneration of fluorenyl and biphenyl quinone methides will also be presented.Key words: quinone methide, biphenyl quinone methide, carbocation, photosolvolysis, photodehydroxylation, hetero-DielsAlder reaction.R6surnC : Les mCthides d'o-et p-quinones (respectivement 2-mCthylknecyclohexa-3,5-dikn-I-one et 4-mCthylknecyclohexa-2,5-dikn-1-one) sont des intermediaires dans une variCtC de systkmes chimiques importants. En particulier, les mCthides d'oquinones sont utiles en synthkse pour la construction de systkmes incorporant le noyau chromane. On fournit un bref rCsumC de l'importance de la chimie des methides de quinone. On prCsente ensuite une revue des Ctudes rCcentes rCalisCes dans notre laboratoire sur des mCthodes efficaces de photogCnCration des mCthides de quinone, en se concentrant sur l'utilisation, en milieux aqueux, d'alcools benzyliques substituCs par des groupes hydroxyles. On montre que cette mCthode est gCnCrale puisqu'elle permet d'obtenir facilement les isomkres ortho, mCta et para des methides de quinone. Lorsqu'ils sont substituts d'une faqon adtquate, tous ces isomkres de methides de quinone ont pu Etre caractCrisCs d'un faqon spectroscopique par photolyse Cclair au laser qui en fait une technique de choix pour I'ttude dynamique de ces intermkdiaires rCactifs. On prCsente aussi le mecanisme de la gCnCration photochimique B partir des alcools hydroxybenzyliques et des extensions de la rCaction B la photogtntration des mCthides de quinones dCrivCs du fluortnyle et du biphinyle.Mots clCs : mtthide de quinone, mCthide de quinone du biphinyle, carbocation, photosolvolyse, photodCshydroxylation, riaction d' hCtCro-Diels-Alder.[Traduit par la ridaction]

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Section: Introductionmentioning

confidence: 99%