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Unformatted text preview: 566 CARBOXYLIC ACID DERIVATIVES: NUCLEOPHILIC ACYL SUBSTITUTION Step 6 is ester saponiﬁcation. It yields a 16-carbon chain having a carboxylic acid function at one
end and an alcohol at the other.
Compound F 1. KOH, ethanol HOC(CH2)5CH 2. H CH(CH2)7CH2OH Compound G
(C16H30O3) In step 7, compound G cyclizes to ambrettolide on heating.
HO O O Compound G 20.35 (a) Ambrettolide This step requires the oxidation of a primary alcohol to an aldehyde. As reported in the literature, pyridinium dichromate in dichloromethane was used to give the desired aldehyde in 84%
CH2Cl2 CH(CH2)7CO2CH3 HCCH Compound A CH(CH2)7CO2CH3
Compound B O
(b) CH Conversion of
appropriate. to @ CH ? CH2 is a typical case in which a Wittig reaction is O
HCCH CH(CH2)7CO2CH3 (C6H5)3P CH2 H2C Compound B (c) CH(CH2)7CO2CH3 Compound C
(observed yield, 53%) Lithium aluminum hydride was used to reduce the ester to a primary alcohol in 81% yield.
H2C CHCH CH(CH2)7CO2CH3 1. LiAlH4
2. H2O H2C Compound C (d ) CHCH CHCH CH(CH2)7CH2OH Compound D The desired sex pheromone is the acetate ester of compound D. Compound D was treated with
acetic anhydride to give the acetate ester in 99% yield.
OO H2C CHCH CH(CH2)7CH2OH CH3COCCH3
pyridine Compound D O
H2C CHCH CH(CH2)7CH2OCCH3 (E )-9,11-Dodecadien-1-yl acetate Acetyl chloride could have been used in this step instead of acetic anhydride.
20.36 Back Forward (a) The reaction given in the problem is between a lactone (cyclic ester) and a difunctional
Grignard reagent. Esters usually react with 2 moles of a Grignard reagent; in this instance Main Menu TOC Study Guide TOC Student OLC MHHE Website ...
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