The Fukuyama reduction is an organic reaction and an organic reduction in which a thioester is reduced to an aldehyde by a silyl hydride in presence of a catalytic amount of palladium. This reaction was invented in 1990 by Tohru Fukuyama.^[1] In the original scope of the reaction the silyl hydride was triethylsilane and the catalyst palladium on carbon:

Fukuyama reductions are used for the conversion of carboxylic acids (as thioester precursor) to aldehydes which is considered a difficult procedure because of the ease of secondary reduction to an alcohol.

The basic reaction mechanism for this reaction takes place as a catalytic cycle:

• Oxidative addition:

  ${\displaystyle {\ce {{R-C(O)-SR}+ Pd^0 -> RC(O)-Pd^{II}-SR}}}$

• Transmetallation:

  ${\displaystyle {\ce {{RC(O)-Pd^{II}-SR}+R3SiH->{RC(O)-Pd^{II}-H}+R3Si-SR}}}$

• Reductive elimination:

  ${\displaystyle {\ce {RC(O)-Pd^{II}-H -> {RC(O)-H}+ Pd^0}}}$

In a variation of the Fukuyama reduction the core BODIPY molecule has been synthesized from the SMe-substituted derivative:^[2] Additional reagents are copper(I)-thiophene-2-carboxylate (CuTC), Pd(dba)2 and tri(2-furyl)phosphine

In the related Fukuyama coupling the hydride is replaced by a carbon nucleophile.