very high regioselectivities for a number of terminal alkenes bearing various functional groups. In one case, the enantiomeric excess of a chiral product, i.e. a 3,5-dimethylhexa-1,4-diene derivative, was determined by chiral RP-HPLC to be 78% ee. The application of cobalt catalysts to the hydrovinylation of unsymmetrical alkenes and 1,3-dienes was investigated using modular phosphine-phosphite ligands
Not a Diels-Alderreaction but a 1,4-hydrovinylation takes place on treatment of 1,3-dienes with functionalized alkenes in the presence of the catalyst system [CoBr2 (dppe)]/ZnI2 /Bu4 NBH4 (dppe = 1,2-bis(diphenylphosphanyl)ethane). With this reaction the 1,4-dienes with different substituents R1 -R4 can be obtained in high selectivity and good to excellent yields.
Regio- and Diastereoselective Michael Additions by Unsymmetrical Allylic Anions Upon Ethyl Propiolate
作者:Ailing Hong、Jonathan M. Friedman
DOI:10.1080/00397919708005003
日期:1997.9
Abstract A convenient and efficient procedure for regio- and diastereoselective addition of prenyl and geranyl anions to ethylpropiolate is reported. This 1,4-addition reaction produces exclusively the trans isomer at the double bond deriving from the triple bond of ethylpropiolate without rearrangement of the starting primary, allylic carbanion nucleophile.