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Unformatted text preview: 486 ENOLS AND ENOLATES 18.29 (a) The ﬁrst conversion is the halogenation of an aldehyde. As described in Section 18.2, this
particular conversion has been achieved in 80% yield simply by treatment with bromine in
CHCl3 Cyclohexanecarbaldehyde 1-Bromocyclohexanecarbaldehyde Dehydrohalogenation of this compound can be accomplished under E2 conditions by treatment with base. Sodium methoxide in methanol would be appropriate, for example, although
almost any alkoxide could be employed to dehydrohalogenate this tertiary bromide.
CH3OH 1-Bromocyclohexanecarbaldehyde (b) Cyclohexene-1carbaldehyde As the reaction was actually carried out, the bromide was heated with the weak base
N, N-diethylaniline to effect dehydrobromination in 71% yield.
Cleavage of vicinal diols to carbonyl compounds can be achieved by using periodic acid
(HIO4) (Section 15.12).
trans-1,2-Cyclohexanediol 1,6-Hexanedial The conversion of this dialdehyde to cyclopentene-1-carbaldehyde is an intramolecular aldol
condensation and is achieved by treatment with potassium hydroxide.
O O O O CH CH CH CH
OH HO CH (c) CH O O Cyclopentene-1carbaldehyde As the reaction was actually carried out, cyclopentene-1-carbaldehyde was obtained in 58%
yield from trans-1,2-cyclohexanediol by this method.
The ﬁrst transformation requires an oxidative cleavage of a carbon–carbon double bond.
Ozonolysis followed by hydrolysis in the presence of zinc is indicated.
2. H2O, Zn CH(CH3)2
4-Isopropyl-1methylcyclohexene Back Forward H2 O Main Menu TOC Study Guide TOC OO
3-Isopropyl-6oxoheptanal Student OLC MHHE Website ...
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This note was uploaded on 09/28/2011 for the course CHM 2210 taught by Professor Reynolds during the Fall '01 term at University of Florida.
- Fall '01
- Organic chemistry