Enhanced cis-selectivities in olefination reactions employing ylides with modified stationary groups
Whereas triphenylphosphonioethanide manifests unsatisfactory cis-selectivities (84.0-95.5%), tris(o,o'-difluorophenyl)- and tri-o-tolylphosphonioethanide react with aliph. or arom. aldehydes and, resp., 2-alkenals or 2-alkynals to afford the olefins with cis/trans-ratios of 99:1 and 96:4 (or better). Triphenylphosphoniobutanide like other higher-homolog std. ylides shows excellent stereoselectivity (99% cis) when condensed with aliph. aldehydes but fails to produce cis-olefins derived from arom. aldehydes with >96% or 97% isomeric purity. In such cases tris(o,o'-difluorophenyl)phosphoniobutanide gave a 99% level of selectivity. [on SciFinder (R)]
1986
40
7-8
246
247
CAN 106:67399
29-7
Organometallic and Organometalloidal Compounds
Inst. Chim. Org.,Univ. Lausanne,Lausanne,Switz.
Journal
written in English.
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