Title of article :
Comparing and taming the reactivity of HWE and Wittig reagents with cyclic hemiacetals
Carrillo، نويسنده , , Jokin and Costa، نويسنده , , Anna M. and Sidera، نويسنده , , Mireia and Vilarrasa، نويسنده , , Jaume، نويسنده ,
Issue Information :
هفته نامه با شماره پیاپی سال 2011
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.
Wittig and HWE reactions , Oxa-Michael cyclisation , Lactols
Journal title :