3-Mercapto-2-butanone

Reaction of 3-mercapto-2-butanone with 3-methoxyacrylate in the presence of NaOMe gives tetrahydrothiophene 471 via intramolecular cyclization of the intermediate 470. Compound 471 is converted into thiophene 472 by treatment with HCl (Scheme 78) <2001JOC2493>. Its cost-effective and scaleable synthesis is also reported <20020PD357>. 

We have reacted natural Diacetyl with natural L-Cysteine to obtain both Tetramethylpyrazine and 3-Mercapto-2-butanone in commercially attractive yields (equation 3). 

An interesting end product, tetramethylpyrazine was also presented in the reaction mixture (27.3% of peak area of the total volatiles). Previous study of the model reaction of 2,3-butanedione and ammonium acetate did not yield any tetramethylpyrazine. It is probably due to the reducing environment provided by H2S which reduced 2,3-butanedione to 3-hydroxy-2-butanone. This explained that both 3-hydroxy-2-butanone and 3-mercapto-2-butanone were found in the reaction mixture. This study also supported the mechanism proposed by Elmore and Mottram 10) who observed that, during the reactions of hydroxyketones with aldehydes and ammonium sulfide, the formation of thiazoles was discouraged due to reducing environment provided by H2S derived from ammonium sulfide. It is also interesting to note that con aring to previous a-hydroxyketone series tetramethylpyrazine was present at trace levels whereas in the a-dicarbonyl series it was the major product under comparable tenq)erature conditions. The reason for this observed phenomenon is not obvious. It is possible that in the reaction system of acetoin and ammonium sulfide, the... 

Fig. 3.23 Formation of 2-furfurylthiol, 2-methyl-3-furathiol, 3-mercapto-2-pentanone and 3-mercato-2-butanone from pentose and cysteine...

One challenge cing the flavor industry today deals witii the stability of process/reaction flavors to heat, UV-light, oxidation, binding to food mafrices, diffusion and interactions with the enviroiunent in v ch they find application. Seeventer et al. (75) studied the stability of thiols formed from model system ribose/cystein, and reported that 2-methyl-3-furandiiol, 2-furfiirylthiol, 2-mercapto-3-butanone and furaneol decreased during storage. In brewed coffee. 

Mercapto-1 -phenyl-2-buten-1 -one, M-00044 1 -Phenyl-3-thioxo-1 -butanone, P-00202... 

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