Question

Question: Synthesize each compound from cyclohexanone and organic halides having $\le$4 C’s. You may use any other inorganic reagents.

a.

b.

c.

Short answer

Answer

a.

b.

c.

Step-by-step solution

Reaction of ketone with alkyl halides in presence of a base.

The reaction of a ketone and an alkyl halide results in the formation of a new carbon-carbon (C-C) bond.

The reaction involves two steps:

Abstraction of an acidic proton (proton adjacent to the carbonyl carbon) from the ketone generating a carbanion.

The attack of the carbanion on the alkyl carbon (of the alkyl halide) and the removal of the halide group.

Gillman reagent

Gilman reagent is a di organocopper reagent (R₂ CuLi) where R represents an alkyl or an aryl group.

Gilman reagent shows conjugate addition on an alpha-beta unsaturated ketone.

Synthesis of the given compounds

a.

Synthesis of a

The reaction of cyclohexanone with LDA and then methyl bromide results in the formation of alpha-methyl cyclohexanone.

The reaction of this compound with LDA and ethyl bromide leads to the substitution of the ethyl group on the other alpha carbon.

b.

The reaction of cyclohexanone with bromine in presence of acetic acid yields bromocyclohexanone .

The reaction of and lithium carbonate yields $\alpha ,\beta$unsaturated cyclohexanone.

The reaction of this compound with the Gilman reagent yields the desired compound.

c.

Synthesis of c

The substitution of alkyl groups on the alpha carbons is carried out using LDA and the appropriate alkyl halide.

The reaction of this compound with bromine molecule (in presence of acetic acid) and lithium carbonate yields the desired product