Highly stereoselective allylic ethylation with alkoxytitanacyclopropane reagents. Synthesis of (1R/S,7R)-1,7-dimethylnonyl propanoate, the Western corn rootworm sex attractant
摘要:
Allylic ethylation of 2-((E)-dodec-2-en-4-yloxy)tetrahydro-2H-pyran with ethylmagnesium bromide in the presence of titanium(IV) isopropoxide proceeds Via a S(N)2' pathway to afford (E)-3-methyltridec-4-ene with excellent syn-diastereoselecivity. This transformation is used as a key step in the synthesis of (1R/S,7R)- 1,7-dimethylnonyl propanoate, the Western corn rootworm (Diabrotica virgifera virgifera) sex attractant. (C) 2008 Published by Elsevier Ltd.
Alkenes from β-lithiooxyphosphonium ylides generated by trapping α-lithiated terminal epoxides with triphenylphosphine
作者:David M Hodgson、Rosanne S D Persaud
DOI:10.3762/bjoc.8.219
日期:——
Terminal epoxides undergo lithium 2,2,6,6-tetramethylpiperidide-induced alpha-lithiation and subsequent interception with Ph(3)P to provide a new and direct entry to beta-lithiooxyphosphonium ylides. The intermediacy of such an ylide is demonstrated by representative alkene-forming reactions with chloromethyl pivalate, benzaldehyde and CD(3)OD, giving a Z-allylic pivalate, a conjugated E-allylic alcohol