4-Chloroisocoumarins can be conveniently prepared from 2-alkynylaryloate esters via the activation of alkynes by electrophilic chlorine, generated in situ from N-chlorosuccinimide (NCS) in the presence of 10 mol % trimethylsilyl chloride (TMSCl), which leads to 6-endo-dig-selective chlorinative annulation to give the desired products in moderate to quantitative yields. The procedure employs readily
Iodine-Mediated Solvent-Controlled Selective Electrophilic Cyclization and Oxidative Esterification of <i>o</i>-Alkynyl Aldehydes: An Easy Access to Pyranoquinolines, Pyranoquinolinones, and Isocumarins
作者:Akhilesh K. Verma、Vineeta Rustagi、Trapti Aggarwal、Amit P. Singh
DOI:10.1021/jo101526b
日期:2010.11.19
provides pyrano[4,3-b]quinolines 4a−f, via formation of cyclic iodonium intermediate Q; however, using alcohols as a solvent as well as nucleophile, o-alkynyl esters 5a−y were obtained selectively in good to excellent yields via formation of hypoiodide intermediate R. Subsequently, o-alkynyl esters were converted in to pyranoquinolinones 6a−i and isocoumarin 6j by electrophilic iodocyclization. This
Iodine-catalyzed and solvent-controlled selective electrophilic cyclization and oxidative esterification of ortho-alkynyl aldehydes
作者:Akhilesh Kumar Verma、Trapti Aggarwal、Vineeta Rustagi、Richard C. Larock
DOI:10.1039/b927185f
日期:——
4-Iodo-pyrano[4,3-b]quinolines and ortho-alkynyl esters were synthesized selectively from ortho-alkynyl aldehydes by an iodine-catalyzed and solvent controlled reaction.
A bromide salt mediated neighboring ester-participated bromocyclization of o-alkynylbenzoates is described here for synthesis of benzil-o-carboxylate. 4-bromoisocoumarins are also reached when phenyl o-alkynylbenzoate is used as the substrate. Mechanism studies suggest that the whole process is comprised by electrophilic bromocyclization and dibromohydration-based ring-opening, and the neighboring
Synthesis of 1,2,3,4-tetrasubstituted naphthalenes through a cascade reaction triggered by silyl acetal activation
作者:Hikaru Yanai、Nobuyuki Ishii、Takashi Matsumoto
DOI:10.1039/c6cc03510h
日期:——
1,2,3,4-Tetrasubstituted naphthalenes bearing four different substituents were synthesized in a regioselective manner by fluoride-induced cascadereaction of lactol silyl ethers, which could be easily prepared from 4-alkynylisocoumarins and ketene silyl...