A first regioselective synthesis of 3-fluoroalkylated benzofurans via palladium-catalyzed annulation of fluorine-containing internal alkynes with variously substituted 2-iodophenol

Metal‐Catalyzed Asymmetric Michael Addition in Natural Product Synthesis

“…[7i] Their synthesis began with reductive coupling between known aldehyde 106 and amine 107,a nd this was followed by tert-butyloxycarbonyl (Boc) group protection.T his process afforded 108 in two steps. Freshly prepared 108 was subjected to an intramolecular Larocka nnulation [42] using [Pd 2 (dba) 3 ]-CHCl 3 /P(tBu) 3 ·HBF 4 as the catalyst [43] to give 3,4-fused benzofuran derivative 109 in 89 % yield. After at wo-step synthesis to give lactone 110,a symmetric Michael addition between lactone 110 and methyl vinyl ketone 111 catalyzed by Sc(OTf) 3 /N,N'-dioxide complex 112 furnished Michael adduct 113 in 85 %yield with 93 % ee.Initially,J ia and co-workersr eported that an amine-thiourea or ab i-Scheme12.…”

“…This process afforded 108 in two steps. Freshly prepared 108 was subjected to an intramolecular Larock annulation using [Pd 2 (dba) 3 ]‐CHCl 3 /P( t Bu) 3 ⋅HBF 4 as the catalyst to give 3,4‐fused benzofuran derivative 109 in 89 % yield. After a two‐step synthesis to give lactone 110 , asymmetric Michael addition between lactone 110 and methyl vinyl ketone 111 catalyzed by Sc(OTf) 3 / N , N ′‐dioxide complex 112 furnished Michael adduct 113 in 85 % yield with 93 % ee .…”

Five‐Membered Heterocycles: Benzofuran and Related Systems

“…Synthesis of 3-fluoroalkylated benzo [b]furans was achieved via a palladium-catalyzed reaction of fluorine-containing internal alkynes with various 2-iodophenols in the presence of P( t Bu) 3 as an essential ligand [28] (Scheme 7.14). …”

Catalytic Asymmetric Total Synthesis of (−)‐Galanthamine and (−)‐Lycoramine

“…[18,19] Av ariety of reaction conditions were screened and we found that under the reaction conditions of [Pd 2 (dba) 3 ]·CHCl 3 (5 mol %) and P(tBu) 3 ·HBF 4 (20 mol %) at 100 8 8C, the desired product 9a was obtained in 95 %y ield (see the Supporting Information). [20] Thesubstrate scope of this reaction was subsequently examined. Thetransformation was found to be quite general, and av ariety of 3,4-fused benzofurans containing either carbon, oxygen, or nitrogen tethers were obtained in reasonable yields ( Table 1).…”