Vinylidene ortho-quinone methides: Unique chiral reaction intermediates in catalytic asymmetric synthesis

Sachie Arae, Masaki Furusawa, Shota Beppu, Kazunobu Igawa, Katsuhiko Tomooka, Ryo Irie

Research output: Contribution to journalArticle

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Abstract

Vinylidene ortho-quinone methides (VQMs) are one-carbon elongated homologues of ortho-quinone methides (QMs), well-known as useful reaction intermediates in organic transformations. These related quinone methides are quite distinct in terms of stereochemistry. Namely, VQMs are characterized by an exocyclic allenyl ketone unit merged with a dearomatized ring system and thus, can be rendered axially chiral by locating a substituent properly at the terminal methylene group of the allene moiety. It should be also noted that VQMs are tautomers of ortho-ethynylphenols and these isomeric species are correlated through a proton-shift (tautomerization). Focusing on these stereochemical and structural features, we have pursued the development of unprecedented asymmetric reactions involving enantioenriched VQM intermediates generated by chiral-basecatalyzed tautomerization of the ethynylphenol precursors. Indeed, commonly used chiral base catalysts such as cinchonine (CN) and cinchonidine (CD) have been successfully demonstrated to be effective to this end. In this account, we wish to briefly describe our recent studies on the asymmetric syntheses of optically active indeno[1,2-c]chromenes, benzofuro[3,2-b]indeno[1,2-c]chromenes, and benzo[a]carbazoles, based on the catalytic enantioselective generation of VQMs with CN or CD and the stereocontrolled intramolecular follow-up cyclization with tethered alkynes, benzofurans, and indoles, respectively.

Original languageEnglish
Pages (from-to)892-899
Number of pages8
JournalChimia
Volume72
Issue number12
DOIs
Publication statusPublished - Jan 1 2018

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Reaction intermediates
Benzopyrans
Benzofurans
Carbazoles
Indoles
Stereochemistry
Alkynes
Cyclization
quinone methide
Ketones
Protons
Carbon
Catalysts

All Science Journal Classification (ASJC) codes

  • Chemistry(all)

Cite this

Vinylidene ortho-quinone methides : Unique chiral reaction intermediates in catalytic asymmetric synthesis. / Arae, Sachie; Furusawa, Masaki; Beppu, Shota; Igawa, Kazunobu; Tomooka, Katsuhiko; Irie, Ryo.

In: Chimia, Vol. 72, No. 12, 01.01.2018, p. 892-899.

Research output: Contribution to journalArticle

Arae, Sachie ; Furusawa, Masaki ; Beppu, Shota ; Igawa, Kazunobu ; Tomooka, Katsuhiko ; Irie, Ryo. / Vinylidene ortho-quinone methides : Unique chiral reaction intermediates in catalytic asymmetric synthesis. In: Chimia. 2018 ; Vol. 72, No. 12. pp. 892-899.
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