Synthesis of 4-Hydroxy-4H-chromenes by Reaction of Salicylic Aldehydes with Alkynals Catalyzed by Silyl Prolinol Ethers
作者:José Alemán、José García Ruano、Cuauhtémoc Alvarado、Vanesa Marcos、Alberto Núñez
DOI:10.1055/s-0030-1260020
日期:2011.6
report an oxa-Michael/Baylis-Hillman tandem reaction between salicylaldehydes and alk-2-ynals activated by silyl prolinol ethers, affording 2,3-disubstituted 4-hydroxy-4H-chromenes in good yields and enantiomeric ratios (up to 98:2). organocatalysis - proline - chromenes - asymmetricsynthesis - aminocatalysis
Enantioselective Synthesis of 4-Isoxazolines by 1,3-Dipolar Cycloadditions of Nitrones to Alkynals Catalyzed by Fluorodiphenylmethylpyrrolidines
作者:José Alemán、Alberto Fraile、Leyre Marzo、José Luis García Ruano、Cristina Izquierdo、Sergio Díaz-Tendero
DOI:10.1002/adsc.201200033
日期:2012.6.18
The first organocatalytic enantioselective 1,3‐dipolar reaction between nitrones and alkynalscatalyzed by (S)‐2‐(fluorodiphenylmethyl)pyrrolidine to give 4‐isoxazolines (2,3‐dihydroisoxazoles) with high enantiomeric excess, excellent yields and low catalyst loading (1–5 mol%) is presented. The catalytic loading could be reduced to 1 mol% with only slight increases in reaction times.