Question

Propose two different methods to synthesize oct-1-en-3-ol $\left[{\mathrm{CH}}_3{\left({\mathrm{CH}}_2\right)}_4\mathrm{CH}\left(\mathrm{OH}\right)\mathrm{CH}={\mathrm{CH}}_{{}_2}\right]$ using a Grignard reagent and a carbonyl compound. Oct-1-en-3-ol is commonly called matsutake alcohol because it was first isolated from the Japanese matsutake mushroom.

Short answer

Grignard reaction is the reaction of an organic compound with an organomagnesium compound called Grignard reagent. It is an important reaction used to make carbon-carbon bonds.

The carbon-magnesium bond in a Grignard reagent is highly polarized, with carbon having a slight negative charge.

This makes carbon a strong nucleophile and can attack electrophilic carbon atoms that are present within polar bonds.

Step-by-step solution

Grignard reaction

Grignard reaction is the reaction of an organic compound with an organomagnesium compound called Grignard reagent. It is an important reaction used to make carbon-carbon bonds.

The carbon-magnesium bond in a Grignard reagent is highly polarized, with carbon having a slight negative charge.

This makes carbon a strong nucleophile and can attack electrophilic carbon atoms that are present within polar bonds.

Reaction of the Grignard reagent with carbonyl compounds

In a reaction between a Grignard reagent and a carbonyl compound, the Grignard reagents act as a nucleophile (carbanion), and carbonyl carbon is the electrophile.

The addition of the Grignard reagent to carbonyl carbon produces an alkoxide ion intermediate which is protonated to form alcohols.

The Grignard reagent converts formaldehyde into primary alcohols, all other aldehydes into secondary alcohols, and ketones into tertiary alcohols.

Carbondioxide reacts with the Grignard reagent to form carboxylic acids.

Synthesis of Matsutake alcohol

Matsutake alcohol or oct-1-en-3-ol is secondary alcohol with a C=C at the alpha position. It can be synthesized by the Grignard reaction.

The carbonyl group from which the alcohol is synthesized can be found by breaking the C-C bond on either side of the hydroxyfunctional group. Therefore, the two possible carbonyl starting materials are:

Starting material 1

Starting material 2

The Grignard reaction of these carbonyls involves the synthesis of an appropriate Grignard reagent and reaction with the carbonyl. The Grignard reagent is synthesized from corresponding alkyl halide using magnesium and dry ether.

Synthesis of Matsutake alcohol from starting material 1:

The reaction uses pentyl magnesium bromide synthesized from Bromo pentane. Therefore, the overall reaction can be given as:

Method 1 for the synthesis of Matsutake alcohol

Synthesis of Matsutake alcohol from starting material 2:

The reaction uses vinyl magnesium bromide synthesized from bromo ethene. Therefore, the overall reaction can be given as:

Second method for the synthesis of Matsutake alcohol