Brønsted acid−catalyzed synthesis of tetrasubstituted allenes and polysubstituted 2H-chromenes from tertiary propargylic alcohols
作者:Natalia Cabrera-Lobera、Noelia Velasco、Roberto Sanz、Manuel A. Fernández-Rodríguez
DOI:10.1016/j.tet.2019.05.023
日期:2019.8
A practical and environmentally benign Brønstedacid−catalyzed protocol for the preparation of all-carbon tetrasubstituted allenes, consisting in the direct SNˈ addition of tri- or dimethoxy arenes or allyltrimethylsilane to tertiary propargylic alcohols, has been developed. In addition, a straightforward synthesis of densely substituted 2H-chromenes by metal-free tandem allenylation/heterocyclization
Palladium-catalyzed deacetonative coupling of aryl propargylic alcohols with aryl chlorides in water
作者:Feng Chang、Yanping Liu
DOI:10.1080/00397911.2017.1297457
日期:2017.5.19
propargylic alcohols with aryl chlorides has been developed. The reaction occurs smoothly in neat water with 2 mol% PdCl2 as catalyst, and various synthetically useful functional groups, including ether, aldehyde, ketone, and heterocyclics, are well tolerated. Moreover, the reaction could proceed through a consecutive Sonogashira/deacetonative process using 2-methyl-3-butyn-2-ol and aryl chlorides as coupling
5-<i>E</i><i>ndo</i>-<i>T</i><i>rig</i> Radical Cyclizations of Bromomethyldimethylsilyl Diisopropylpropargylic Ethers. A Highly Diastereoselective Access to Functionalized Cyclopentanes
An efficient radical sequence involving a 5-exo-dig, a diastereoselective 1,5-H transfer, and a rarely observed in an all-carbon system 5-endo-trig cyclization allows the construction of cyclopentyl derivatives 2 bearing four controlled stereogenic centers from diisopropyl precursors 1. Olefins 3 were also isolated as minor side products. The effect of the acetylenic substituent Y has been investigated
The efficient addition of terminal alkynes to aldehydes or ketones to give propargyl alcohols in yields of 66-96 % can be achieved by activation with catalytic amounts of CsOH⋅H2 O [Eq. (a)]. A CsOH-catalyzed addition of acetonitrile derivatives to terminal alkynes is also possible.
Mild and Solvent‐Free Alkynylation of Ketones on the KF/Alumina