H2‐O‐T! Aromatic O‐heterocycles are a challenging substrates for asymmetrichydrogenation (H2). An in situ formed chiral N‐heterocyclic carbene (NHC) ruthenium complex allows the high yielding, completely regioselective, and highlyasymmetrichydrogenation of substituted benzofurans at room Temperature, giving valuable 2,3‐dihydrobenzofurans (see scheme).
H 2 ‐O‐T!芳族O杂环是不对称氢化(H 2)的具有挑战性的底物。原位形成的手性N-杂环卡宾(NHC)钌络合物可在T温度下以高收率,完全区域选择性和高度不对称氢化取代苯并呋喃,得到有价值的2,3-二氢苯并呋喃(参见方案)。
Anti-Markovnikov Hydroheteroarylation of Unactivated Alkenes with Indoles, Pyrroles, Benzofurans, and Furans Catalyzed by a Nickel–<i>N</i>-Heterocyclic Carbene System
作者:York Schramm、Makoto Takeuchi、Kazuhiko Semba、Yoshiaki Nakao、John F. Hartwig
DOI:10.1021/jacs.5b08039
日期:2015.9.30
benzofurans, and furans, to unactivated terminal and internal alkenes. The reaction is catalyzed by a combination of Ni(COD)2 and a sterically hindered, electron-rich N-heterocyclic carbene ligand or its analogous Ni(NHC)(arene) complex. The reaction is highly selective for anti-Markovnikov addition to α-olefins, as well as for the formation of linear alkylheteroarenes from internal alkenes. The reaction occurs
Reaction of alkynyl(p-phenylene)bisiodonium ditriflates (2) with sodiumphenoxide in methanol provides 2-substituted benzofurans (3). This result indicates that β-phenoxyalkylidenecarbenes generated by the reaction with phenoxide anion undergo novel intramolecular aromatic CH insertion to afford benzofurans.
One-Pot Synthesis of Substituted Benzo[<i>b</i>]furans from Mono- and Dichlorophenols Using Palladium Catalysts Bearing Dihydroxyterphenylphosphine
作者:Miyuki Yamaguchi、Haruka Katsumata、Kei Manabe
DOI:10.1021/jo401503t
日期:2013.9.20
on the phosphorus atom (Cy-DHTP) was found to be a powerful ligand for the palladium-catalyzed one-potsynthesis of substituted benzo[b]furans from 2-chlorophenols and terminal alkynes. This catalyst system was also applicable to the sequential one-potsynthesis of disubstituted benzo[b]furans from dichlorophenols via the Suzuki–Miyaura cross-coupling of chlorobenzo[b]furan with boronic acids. The use
发现在磷原子上带有环己基的二羟基叔苯基膦(Cy-DHTP)是钯催化由一锅法从2-氯酚和末端炔烃合成取代苯并[ b ]呋喃的强配体。该催化剂体系还适用于通过氯苯并[ b ]呋喃与硼酸的Suzuki-Miyaura交叉偶联从二氯苯酚一步法一锅合成二取代的苯并[ b ]呋喃。Cy-DHTP和XPhos这两种配体的使用是促进反应的关键。机理研究表明,Pd–Cy-DHTP催化剂是Sonogashira交叉偶联步骤中的活性物种,而Pd–XPhos催化剂则加速了Suzuki–Miyaura交叉偶联步骤。
One-pot synthesis of 2,3-disubstituted benzofurans from 2-chlorophenols using palladium–dihydroxyterphenylphosphine catalyst
2,3-Disubstituted benzofurans possessing 2-hydroxyphenyl moiety at the C-3 position were synthesized from readily available 2-chlorophenols and terminal alkynes by hydroxy-directed ortho-Sonogashira coupling and subsequent oxypalladation/reductive elimination, using Pd-dihydroxyterphenylphosphine catalyst. The catalyst accelerates not only the Sonogashira coupling but also the introduction of 2-hydroxyphenyl