Synthesis of 3,4-Disubstituted 2H-Benzopyrans through C−C Bond Formation via Electrophilic Cyclization

Abstract

The electrophilic cyclization of substituted propargylic aryl ethers by I2, ICl, and PhSeBr produces 3,4-disubstituted 2H-benzopyrans in excellent yields. This methodology results in vinylic halides or selenides under mild reaction conditions and tolerates a variety of functional groups, including methoxy, alcohol, aldehyde, and nitro groups.

Expedient Syntheses of β‐Iodofurans by 5‐endo‐dig Cyclisations

“…These now form a considerable body of methodology, very recently exemplified and summarised by the Larock group. [18] Hence, this general type of cyclisation can now be regarded as a generally useful synthetic method. The present approach to β-iodofurans exemplifies this and has potential as a general furan synthesis.…”

Fast Synthesis of Benzofluorenes by Selenium‐Mediated Carbocyclizations

“…[2] The electrophilic cyclization of substituted propargylic aryl ethers by phenyl selenenyl bromide produces 3,4-disubstituted 2H-benzopyrans in excellent yields. [3] Spirocompounds can also be synthesized by a titanium tetrachloride promoted transfer of a phenylseleno moiety in a-phenylseleno alkenyl ketones. [4] More recently, asymmetric versions of the selenium-mediated carbocyclizations have been reported.…”

Synthesis of Naphthofurans by tBuOK‐Catalyzed Intramolecular Anionic Cycloaddition of Unsymmetrical Bis‐propargyl Ethers

“…[7] Up to now, the most useful methodology described for the preparation of these heterocycles is intermolecular annulation. Transition-metalcatalyzed [8] and electrophilic cyclization reactions [9] are extensively employed as powerful tools in intermolecular annulation. Such processes generally proceed through the activation of the triple bond of either terminal or internal alkynes followed by intramolecular nucleophilic attack on the activated triple bond.…”