Extended Corey–Chaykovsky reactions: transformation of 2-hydroxychalcones to benzannulated 2,8-dioxabicyclo[3.2.1]octanes and 2,3-dihydrobenzofurans

Abstract

We report the divergent synthesis of benzannulated 2,8-dioxabicyclo[3.2.1]octanes and 2,3-dihydrobenzofurans using the concept of the extended Corey-Chaykovsky reactions. With this concept, 2-hydroxychalcones were treated with the Corey ylide providing highly...

Extended Version of the Corey–Chaykovsky Reaction: Synthesis of 2,4-Substituted Furans by the Treatment of β-Dialkylamino Chalcones with Dimethylsulfonium Methylide

“…■ EXPERIMENTAL DETAILS General Information. 1 H and 13 C { 1 H} NMR spectra were recorded with a Bruker Avance III HD 400 (400 MHz for 1 H and 100 MHz for 13 C { 1 H} NMR) spectrometer at room temperature; the chemical shifts (δ) were measured in ppm with respect to the solvent (CDCl 3 , 1 H: δ = 7.26 ppm, 13 C { 1 H}: δ = 77.16 ppm; DMSO-d 6 , 1 H: δ = 2.50 ppm, 13 C { 1 H}: δ = 39.52 ppm). Coupling constants (J) are given in hertz.…”

“…1 H NMR (400 MHz, CDCl 3 ) δ = 7.62−7.60 (m, 2H), 7.42 (s, 1H), 7.31−7.26 (m, 3H), 7.18−7.11 (m, 4H), 6.72 (s, 1H), 2.32 (s, 3H) ppm; 13 C { 1 H} NMR (100 MHz, CDCl 3 ) δ = 154. 3, 139.9, 136.2, 132.7, 131.3, 131.1, 129.6, 129.2 (2C), 128.1, 128.0, 127.8, 126.4, 124.3 (2C) 7.75 (m, 2H), 7.50 (br s, 1H), 7.47−7.43 (m, 4H), 7.34−7.28 (m, 2H), 7.11−7.09 (m, 1H), 2.36 (s, 3H) ppm; 13 C { 1 H} NMR (100 MHz, DMSO-d 6 ) δ = 153. 9, 138.9, 137.9, 131.6, 130.1, 128.8 (2C), 128.6, 127.8, 127.7, 127.6, 126.0, 123.4 (2C), 122.6, 104.4, 20.9…”

“…Yield 195 mg (78%), pale yellow oil. 1 H NMR (400 MHz, CDCl 3 ) δ = 7.60−7.58 (m, 2H), 7.55 (s, 1H), 7.34−7.32 (m, 2H), 7.30−7.26 (m, 2H), 7.18−7.12 (m, 1H), 6.83−6.81 (m, 2H), 6.78 (s, 1H), 3.71 (s, 3H) ppm; 13 C { 1 H} NMR (100 MHz, CDCl 3 ) δ = 158. 8,154.6,137.0,130.7,128.5 (2C),127.9,127.3,126.8 (2C),124.9,123.7 (2C),114.2 (2C),103.9,.…”

“…12 This process can be referred to as the extended Corey−Chaykovsky reaction. 13 Its realization is presumably resulted from the heterolysis of the C−O bond in the formed vinyloxiranes due to the excellent stabilization of the cationic center in the zwitter-ionic intermediate. Similar behavior was earlier described for some other enones containing substituents stabilizing efficiently the positive charge at the β-carbon atom that facilitates the vinyloxirane expansion to dihydrofuran.…”

α,β-Unsaturated Carbonyls for One-Pot Transition-Metal-Free Access to 3,6-Dihydro-2H-pyrans

“…Our group has been using the Corey–Chaykovsky ylide widely for the synthesis of donor–acceptor cyclopropanes and cyclopropane mono-carbonyls that were then used in numerous transformations to construct diverse hetero and carbocyclic systems. Over the years, CCR has broadly been explored for small ring synthesis; however, there are very limited reports on utilizing its reaction conditions for the construction of larger rings (five- or six-membered) and generally are not thoroughly studied . Nevertheless, it has always been fascinating to see if something unprecedented can be mined out of a well-known reaction condition, and in this direction, we anticipated using the Corey–Chaykovsky ylide for the construction of an epoxide adjacent to a reactive cyclopropanean epoxycyclopropane.…”