Regioselective synthesis of dihydrofurans from 2,2-dibromo 1,3-diones and olefins using copper

Hexafluoro‐2‐Propanol‐Promoted Electro‐Oxidative [3+2] Annulation of 1,3‐Dicarbonyl Compounds and Alkenes

“…Therefore, numerous methods to build this structural motif have been developed over the past decades. Undoubtedly, the most attractive strategy is the oxidative [3+2] annulation between 1,3‐dicarbonyl compounds and alkenes . However, stoichiometric strong oxidants, transition metal salts, harsh reaction conditions or pre‐functionalized substrates are indispensable in the reported literatures employing the [3+2] annulation strategy (Scheme a).…”

“…Undoubtedly, the most attractive strategy is the oxidative [3 + 2] annulation between 1,3-dicarbonyl compounds and alkenes. [7][8][9][10][11][12][13][14][15][16][17] However, stoichiometric strong oxidants, transition metal salts, harsh reaction conditions or pre-functionalized substrates are indispensable in the reported literatures employing the [3 + 2] annulation strategy (Scheme 1a). Due to the existence of these drawbacks, it is imperative to develop a method fulfilling the demands of green and sustainable chemistry.…”

Selectivity in cyclopropanations and 1,3-cycloadditions in transition metal-catalyzed decompositions of 2-diazocyclohexane-1,3-diones and the corresponding phenyliodonium ylides

“…The structure of 10a was established by comparison of the spectral data with those of the known product resulting from reaction of 2,2-dibromodimedone with styrene in the presence of copper. 13 The origin of the cycloadduct is not clear. The reaction of 1b in the presence of [Rh 2 {(S)-nttl} 4 ] resulted only in racemic cyclopropane 9a and racemic cycloadduct 10a.…”

“…The structure of the adducts is consistent with the higher polar character of the ketone group over that of the ester function. It was tentatively assigned for 12 on the grounds of 13 C NMR shift calculations using SpecTool. 14 The signals attributed to C(3b), C (4) The X-ray structure of 12 confirms the tentative assignement.…”

Synthesis of 4-hydroxy-1-methylindole and benzo[b]thiophen-4-ol based unnatural flavonoids as new class of antimicrobial agents☆

“…Easy and efficient methods are available for synthesis of 2-substitutedtetrahydrobenzofurans, but these methods can only be applied for synthesis of 2,3-dihydro-2-substituted-tetrahydrobenzofurans due to their limitations. 15,16 Recent studies have shown use of rhodium acetate in dipolar cycloaddition of diazacyclohexane-1,3-diones with vinyl acetates followed by acid catalyzed dehydration to produce 1 in 41-71% yield. 17 Our attempt to synthesize 1, commenced from commercially available cyclohexane-1,3-dione as shown in Scheme 1.…”