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Lithium cyclohexyl isopropylamide

Treatment of 20 with potassium fer -butoxide in tetrahydrofuran at — 80C C gave high dia-stereoselectivity and high yields in the intramolecular cyclization. Interestingly, the potassium butoxide must be wet, i.e., partly decomposed to achieve the best results. Lithium cyclohexyl-isopropylamide gave mediocre results123. With the unusual base system [/-BuOK (3.6 equiv) + H20 (1.8 equiv)] (1 S,2R)-trans-l was isolated in 85% yield and with 96.5% stereoselectivity. [Pg.755]

Regioselective reductions of the maleic anhydride derivatives (387) and (389) with lithium aluminum hydride yielded (388) and (390). Metallation of the O-methyltetronic acid (388) with lithium N- cyclohexyl-A- isopropylamide followed by treatment with, for example, p-anisaldehyde led to pulvinones such as (391) (79JCS(P1)70). [Pg.697]

Nevertheless, diastereomeric product 26 was used to test the validity of the Claisen approach. Thus, esterification of 26 with propionic anhydride offered the requisite ester 15 along with the inseparable diastereomer 15a (1 1 ratio). Kinetic deprotonation of the mixture of 15/15a was effected with lithium N-cyclohexyl-lV-isopropylamide (LICA) and, upon warming to room temperature, Ireland-Claisen... [Pg.131]


See other pages where Lithium cyclohexyl isopropylamide is mentioned: [Pg.214]    [Pg.1038]    [Pg.1310]    [Pg.56]    [Pg.329]    [Pg.161]    [Pg.112]    [Pg.47]   
See also in sourсe #XX -- [ Pg.214 ]




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