Benzaldehyde → Benzyl Alcohol

HRID 425267Notes

Reaction equation

HRID 425267 reaction equation
B.[CH:2](=[O:9])[C:3]1[CH:8]=[CH:7][CH:6]=[CH:5][CH:4]=1.C(C1C=CC=CC=1)(=[O:12])C.B.[CH2:20]([C:22]1[CH:23]=[CH:24][C:25]([CH3:28])=N[CH:27]=1)[CH3:21]>>[CH2:2]([OH:9])[C:3]1[CH:8]=[CH:7][CH:6]=[CH:5][CH:4]=1.[CH2:21]([OH:12])[CH2:20][C:22]1[CH:23]=[CH:24][CH:25]=[CH:28][CH:27]=1

Participants

6

Reactant 4

HCID 240Benzaldehyde2×HCID 6331BoraneHCID 7410AcetophenoneHCID 178419175HCID 178419175, compound

Product 2

HCID 244Benzyl AlcoholHCID 60542-Phenylethanol

Procedure

The chemoselectivity of the new borane complexes with substituted pyridines (1) in reduction reactions was investigated in a competitive reactivity study by reacting equimolar amounts of benzaldehyde and acetophenone with 5-ethyl-2-methylpyridine borane (1 equivalent of borane hydride relative to 1 equivalent of benzaldehyde, see example 10). The reaction was immediate and exothermic taking the reaction temperature to 70° C. The benzaldehyde was reduced much faster than the ketone, resulting in a 91:9 ratio of benzyl alcohol to phenethylalcohol. Of the combined carbonyl substrates, 37% was reduced and 63% remained unreduced (50% expected), which indicated that two of the three available hydride atoms were available for the reduction under these conditions. It is common that carbonyl reductions with borane frequently stop when two of the three borane hydride atoms have reacted, owing to the poor reactivity of the dialkoxyborane [(RO)2BH] species formed.

Workup

  1. customto 70° C

Sources & evidence

ORD record
ord-a54b26dc373142edb6b18f4fa5dbe49d
Source dataset
uspto-grants-2012_01
Patent number
US08106200B2

Reaction notes

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