Fluorinated Furan‐2(5H)‐ones: Reactivity and Stereoselectivity in Diels–Alder Reactions

Abstract

3-Fluorofuran-2(5H)-one (1) and three 3,4-difluorofuran-2(5H)-ones 2-4, α,β-unsaturated lactones possessing fluorinated double bonds, were applied as dienophiles in DielsAlder reactions with normal electron demand using diphenylisobenzofuran or cyclopentadiene as dienes. In the same reactions, furan or 2,3-dimethylbuta-1,3-diene were completely unreactive. Three structural factors of furan-2(5H)-ones appeared to have an effect on the reactivity, regioselectivity and diastereoselectivity of the [4+2] cycloadditions: the number of fluorine atoms attached to the double bond and the number and the bulkiness of alkyl substituents at the 5-position of the furan-2(5H)-one system. The monofluorinated furan-2(5H)-one 1 was generally more reactive than the difluorinated furan-2(5H)-ones 2-4. While the reactions of the furan-2(5H)-ones 2-4 with isobenzofuran exclu-

Addition of Nucleophiles to Fluorinated Michael Acceptors

“…In contrast to earlier oxidations of such fluorinated allylic alcohols by Swern oxidation,26c,26d Dess–Martin periodinane (DMP) oxidation resulted in almost quantitative yields of the desired 2‐fluoro‐α,β‐unsaturated carbonyl compounds (i.e., 7a – 7d ) without purification (Scheme ).…”

Synthesis and Diels–Alder reactions of α-fluoro- and α-trifluoromethylacrylonitriles

“…Electron-withdrawing substituents such as carbonyl functions, sulfoxide or sulfonyl groups attached to the fluorovinyl moiety increase the reactivity of the dienophiles. Therefore, 2-fluoroacroleins [47,48], a,b-unsaturated a-fluorocarboxylic acid derivatives [49][50][51][52][53][54], and unsaturated a,b-difluoroketones [55,56], b-fluoroalkylated enones [57], fluorinated furan-2(5H)-ones [58], fluorinated vinylsulfones [59,60] or an electron-poor fluorinated vinyl sulfoxide [61] were shown to be moderate or good dienophiles. So, we decided to use prepared nitriles for Diels-Alder reactions.…”

Unusual β,β′-coupling and β-alkylation of methyl 2,3,3-trifluoropropenoate by lithium diorganocuprates

“…Trifluoroacrylates have been reported as useful building blocks in syntheses of lactones or 2,3-difluoro-2,3-unsaturated esters [1][2][3][4][5][6], which have been in turn exploited as convenient synthetic intermediates [7][8][9]. Recently, b-fluoroalkylation of benzyl trifluoroacrylate by fluorine vinylic substitution using Grignard reagents in the presence of copper(I) bromide has been reported [5,6].…”