DIBAL-H Reduction

General Procedure (Ester to alcohol & Nitrile to Aldehyde):

To a solution of Ester or Nitrile (1 eq.) in DCM or THF or toluene at -78 ^oC is added DIBAL-H in THF or toluene (1M solution, 1 eq.) dropwise and maintained at -78 ^oC under nitrogen atmosphere for 2 h. It is slowly brought to room temperature and continued stirring for additional 6 h. The reaction is monitored by TLC. The reaction is quenched by adding methanol slowly, followed by addition of aqueous Rochelle’s salt solution. The resultant suspension is filtered through celite and washed with ethyl acetate/DCM. The layers are separated. The organic layer is then successively washed with water (10 Vol x 2) and brine solution, dried over sodium sulphate, filtered and concentrated under reduced pressure to get the desired compound. The crude product is purified by column chromatography.

General Procedure (Ester to aldehyde at -78 ^oC):

To a solution of Ester (1 eq.) in DCM or THF or toluene at -78 ^oC is added DIBAL-H in THF or toluene (1M solution, 1 eq.) dropwise and maintained at -78 ^oC under nitrogen atmosphere for 2 h (It is important to maintain the temp. at or below -78 ^oC to ensure further reduction does not occur). The reaction is monitored by TLC. The reaction needs to be maintained at -78 ^oC throughtout.

The reaction is quenched by adding methanol slowly, followed by addition of aqueous Rochelle’s salt solution. The resultant suspension is filtered through celite and washed with ethyl acetate/DCM. The layers are separated. The organic layer is then successively washed with water (10 Vol x 2) and brine solution, dried over sodium sulphate, filtered and concentrated under reduced pressure to get the desired compound. The crude product is purified by column chromatography.

DIBAL shall be quenched by several other methods (Quenching methods of LAH and DIBAL are almost same)

(a) by adding water (1 Vol) , 10 % NaOH (1.5 Vol), and finally again water (3 Vol).

(b) by adding saturated aqueous Na₂SO₄

(c) by adding aqueous solution of Rochelle’s salt (sodium potassium tartrate, KNaC₄H₄O₆)

• Quenching reactions: Aluminium based reagents (LibreTexts Chemistry) – LAH & DIBAL-H

Note:

• DIBAL-H reduces (a) esters to alcohols, (b) nitrile to aldehyde and (c) Lactone to Lactol

• If the reaction is maintained at -78 ^oC, DIBAL-H reduction of ester results in aldehyde (partial reduction). However, it is bit difficult to control DIBAL-H reduction to stop at aldehyde stage

For more details on reactions and reagents, 
refer to the tab "Reaction, Reagents and Mechanism"

Typical Procedure:

Ester to Alcohol using DIBAL:

• Ester reduction (ChemSpider) – Ester to Alcohol — Open access

• Ester to Alcohol-1 (OrgSyn) — Open access

• Ester to Alcohol-2 (OrgSyn) — Open access

Lactone to Lactol using DIBAL:

• Reduction of chroman-2-ones to lactols using diisobutylaluminium hydride (ChemSpider) – Lactone to Lactol — Open access

• Lactone to Lactol-1 (OrgSyn) — Open access

Ester to Aldehyde (partial reduction) using DIBAL:

• Dibal reduction of an amino acid derived methyl ester (ChemSpider) -Ester to Aldehyde (partial reduction at low temp.) — Open access

• Ester to Aldehyde-1 (OrgSyn)- Partial reduction at low temp. — Open access

• Ester to Aldehyde-2 (OrgSyn)- Partial reduction at low temp. — Open access

• Ester to Aldehyde-3 (OrgSyn)- Partial reduction at low temp, followed by Grignard — Open access

For more details on reactions and reagents, 
refer to the tab "Reaction, Reagents and Mechanism"

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