Aluminum hydride, diisobutyl- DIBAL carboxylic acids

Acylthiazolidine-2-thiones (593), easily prepared from carboxylic acids and thiazolidine-2-thione, can be reduced to the corresponding aldehydes with diisobutyl-aluminum hydride in toluene at -78 to -40 °C in 70-90% yield or with lithium tri-f-butoxyaluminum hydride in THF at -20 to 0 °C in 80-90% yield (Scheme 130) (79BCJ555). The formation of the aluminum-containing six-membered chelate (594) in this reaction process is probable and is supported by the fact that no decrease in yield is observed on changing the mole ratio of DIBAL from 1.2 to 2.1 equivalents. 

The aldehyde intermediate can be isolated if 1 equivalent of diisobutyl-aluminum hydride (DIBAH, or DIBAL-H) is used as the reducing agent instead of UAIH4. The reaction has to be carried out at -78 °C to avoid further reduction to the alcohol. Such partial reductions of carboxylic acid derivatives to aldehydes also occur in numerous biological pathways, although the substrate is either a thioester or acyl phosphate rather than an ester. 

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See also in sourсe #XX -- [ , ]

See also in sourсe #XX -- [ , , ]

See also in sourсe #XX -- [ , , ]

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