Comparing and taming the reactivity of HWE and Wittig reagents with cyclic hemiacetals |
| |
Authors: | Jokin CarrilloAnna M Costa Mireia SideraJaume Vilarrasa |
| |
Institution: | Departament de Química Orgànica, Facultat de Química, Universitat de Barcelona, Diagonal 647, 08028 Barcelona, Catalonia, Spain |
| |
Abstract: | A practical solution to the formation of mixtures of E/Z and open/cyclic isomers in the reaction of (2R,4S)-4-hydroxy-2-methylpentanal (as its hemiacetal, a lactol) with conjugated phosphoranes (stabilised Wittig reagents) and Horner-Wadsworth-Emmons reagents is disclosed. The HWE reaction has a strong bias to give oxolanes. On the other hand, stabilised Wittig reagents give unsaturated carboxyl derivatives of configuration E (major) and oxolanes (minor); the latter can be avoided by addition of CF3CH2OH or using morpholine amide phosphorane. |
| |
Keywords: | Lactols Wittig and HWE reactions Oxa-Michael cyclisation |
本文献已被 ScienceDirect 等数据库收录! |
|