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Solvent Dependent Divergent Reactivity of Electron‐Rich Dienones with and without Visible Light: Access to Cyclopropanated Furans and Butenolides
Author(s) -
Saha Jayanta,
Das Indrajit
Publication year - 2020
Publication title -
advanced synthesis and catalysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.541
H-Index - 155
eISSN - 1615-4169
pISSN - 1615-4150
DOI - 10.1002/adsc.201901273
Subject(s) - chemistry , photochemistry , catalysis , reactivity (psychology) , intramolecular force , solvent , isomerization , reagent , lewis acids and bases , redox , ionic bonding , electron transfer , medicinal chemistry , organic chemistry , medicine , alternative medicine , pathology , ion
Visible light excitation of electron‐rich dienones in isopropanol solvent under ambient conditions using hexafluoroisopropanol (HFIP) as an additive promotes intramolecular radical cascade cyclization to afford cyclopropanated furans. Molecular dioxygen in the air serves as a redox catalyst in this reaction which is proposed to proceed through a radical cation intermediate generated by single‐electron transfer (SET) from a phototransient dienone to oxygen. By changing the solvent from isopropanol to HFIP, exclusive formation of substituted butenolides occurs via ionic cascade cyclization involving E → Z isomerization/lactonization/thiolate addition. HFIP is assumed to act as a medium, hydrogen bond donor catalyst, and a Lewis acid substitute as well. This reaction may be conducted even in the absence of light and no catalyst or reagent is required.