Versatile synthesis of (Z)-1-alkylidene-1,3-dihydroisobenzofurans and 1H-isochromenes by palladium-catalyzed cycloisomerization of 2-alkynylbenzyl alcohols
An easy synthesis of (Z)-1-alkylidene-1,3-dihydroisobenzofurans and 1H-isochromenes by palladium-catalyzedcycloisomerization of readily available 2-alkynylbenzyl alcohols under neutral conditions is reported. Reactions were carried out at 70–100°C in the presence of catalytic amounts (1–2%) of PdI2 in conjunction with 2 equiv. of KI for 1.5–24 h. The preference towards the 5-exo-dig cyclization mode
Bromotrimethylsilane (TMSBr)-promoted intramolecular cyclization of (o-arylethynyl)benzylethers to form 1H-isochromenes at room temperature is reported. Further studies indicated that vinyl carbocations are the reaction intermediates which are stabilized by the conjugated aryl groups. Thus, O-addition of benzylethers/tetrahydropyrans to alkynes was achieved under metal-free, acidic conditions. These
报道了溴代三甲基硅烷 (TMSBr) 促进的 ( o -arylethynyl) 苄基醚在室温下分子内环化形成 1 H-异色烯。进一步的研究表明,乙烯基碳阳离子是由共轭芳基稳定的反应中间体。因此,在无金属、酸性条件下实现了苄基醚/四氢吡喃与炔烃的O-加成。这些反应条件与炔基普林斯反应相容;因此,使用一锅法直接由炔基苯甲醛和炔醇生产1 H-异色烯。
FeCl3·6H2O-catalyzed facile and efficient synthesis of pyrano[4,3-b]quinolines and isochromenes
作者:Mrityunjaya Asthana、Jay Bahadur Singh、Radhey M. Singh
DOI:10.1016/j.tetlet.2015.12.102
日期:2016.2
developed for the synthesis of 1,3-disubstituted 1H-pyrano[4,3-b]quinolines from o-arylethnylquinonylmethanol via 6-endo-dig cyclization of alcoholic –OH onto alkynes in good to excellent yields. The reaction conditions were successfully exploited on primary and tertiary alcohol analogs. The reagent was further generalized with the aromatic alcohol analogs providing the synthesis of isochromenes in
廉价的1摩尔%的FeCl 3 ·6H 2 ö试剂已经被用于合成开发1,3-二取代1 ħ吡喃并[4,3- b ]喹啉由ö经由6 -arylethnylquinonylmethanol -内将醇-OH环化成良好至优异收率的炔烃。反应条件已成功地用于伯醇和叔醇类似物。该试剂进一步用芳族醇类似物泛化,从而以高收率合成了异色烯。从伯醇到仲醇到叔醇的反应速率和产率的提高可以归因于烷基的诱导作用,其增强了羟基的亲核性并加速了环化模式。
Gold‐Catalyzed Carbocyclization/C=N Bond Formation Cascade of Alkyne‐Tethered Diazo Compounds with Benzo[
<i>c</i>
]isoxazoles for the Assembly of 4‐Iminonaphthalenones and Indenes
作者:Ming Bao、Xiongda Xie、Wenhao Hu、Xinfang Xu
DOI:10.1002/adsc.202100602
日期:2021.8.13
carbocyclization/C=Nbondformation cascade reaction has been developed for the synthesis of polyfunctionalized 4-iminonaphthalenones and indenes in good to high yields under mild reaction conditions. The reaction goes through 5/6-endo-dig diazo-yne carbocyclization to form the endocyclic vinyl carbene species from corresponding alkyne-tethered diazo compounds, followed by electrophilic addition/N−O bond cleavage/aromatization
2‐Substituierte Benzylbromide mit Carbonylfunktion in der Seitenkette sind in 2stufiger Reaktion aus 3‐substituierten Isocumarinen durch Lithiumalanatreduktion zu 3‐substituierten Isochromenen und deren Spaltung mit Bromwasserstoff zugänglich. Reaktionsprodukte und Mechanismus der Lithiumalanatreduktion werden diskutiert.