Big Chemical Encyclopedia

Chemical substances, components, reactions, process design ...

Articles Figures Tables About

Horner-Wadsworth-Emmons oxaphosphetane

Oxaphosphetane Fragmentation, Last Step of Wittig and Horner-Wadsworth-Emmons Reactions... [Pg.196]

Fig. 4.41. A HetVHet2 elimination from the presumed oxaphosphetane intermediate of a Horner-Wadsworth-Emmons reaction... Fig. 4.41. A HetVHet2 elimination from the presumed oxaphosphetane intermediate of a Horner-Wadsworth-Emmons reaction...
The mechanism of the Horner-Wadsworth-Emmons reaction of the lithium enolate derived from trimethyl phosphonoacetate with acetaldehyde has been investigated by ab initio calculations. Oxaphosphetane formation is rate determining, both in the gas phase and with one ether moleeule solvating. The transition state leading to trans-alkene is more stable than that giving the cis form. [Pg.22]

Ab initio calculations (RHF/6-31 -1- G ) have revealed that the Horner-Wadsworth-Emmons reaction of (Me0)2P0CHLiC02Me with ethanal occurs by carbonyl addition, rate-determining (in the gas phase or in the presence of one molecule of Mc20) oxaphosphetane formation, pseudorotation, P—C bond cleavage, and then O-C bond cleavage. The observed preference for rranx-relative to cts-alkene formation is consistent with the predicted transition-state stabilities. [Pg.385]

See other pages where Horner-Wadsworth-Emmons oxaphosphetane is mentioned: [Pg.15]    [Pg.472]    [Pg.361]    [Pg.362]    [Pg.44]    [Pg.180]    [Pg.15]   
See also in sourсe #XX -- [ Pg.165 ]



SEARCH



Emmons

HORNER WADSWORTH - EMMONS

Oxaphosphetane

Oxaphosphetanes

Wadsworth-Emmons

© 2024 chempedia.info