Acylthio

Acylthio-4,5-dihydro-l,3-thiazole werden durch Bis-[2-methyl-propyl]-aluminiumhydrid mit guten Aus-beuten zu Aldehyden reduziert1. 

Acylthio-3-nitropyridines, prepared from the corresponding carboxylic acids, have been used as acylating agents when the corresponding acid chlorides are unstable [426]. 

Unabhangig wird eine analoge Reaktionssequenz unter Bildung eines 2-Acylthio-4,5-dihydro- 1,3-thiazols beschrieben250 ... 

Sodium/ammonia treatment also causes disruption of the ring in thiophene and simple thiophenes, however thiophene-2-carboxylic acid and 2-acylthio-phenes can be converted into the 2,5-dihydro-derivatives using lithium in ammonia. Side-chain reductions can be achieved selectively with reagents such as metal hydrides, which do not affect the ring. 

Nucleophilic replacement reactions (by AcS, Ph CO S , MeS , and PhCHaS") with methyl 0-toluene-p-sulphonyl-L-lactate and sodium L-2-chloropropionate give 2-acylthio- and 2-alkylthio-D-propionic acids and esters. Extensive racemization accompanies the use of excess thio-acetate or thiobenzoate, due to further 5 2 replacement reactions, as observed for LiAlH4 reduction of L-(2-methylthio)propionic acid or its methyl ester. Diborane reduction gives optically pure L-(2-methylthio)-propanol, however. This work includes a new synthesis of ( + )-2-mercaptopropionic acid, though by known methods, and establishes the D configuration for this isomer. 

Carbonyl Activation. The title reagent (1) reacts with acyl chlorides to produce 2-acylthio-l-methylpyridinium salts (2) as stable hygroscopic solids (eq 1). These may then be treated with a variety of oxygen and nitrogen nucleophiles in the presence of base to effect transfer of the acyl group to the nucleophilic species to produce (3) and regenerate (1). ... 

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