BETA-KETO SULFOXIDES .6. CONVERSION OF OMEGA-(METHYLSULFINYL)ACETOPHENONE INTO DI- AND TRI-OMEGA-(METHYLMERCAPTO)ACETOPHENONE . SYNTHESIS OF ALPHA-HYDROXY ALDEHYDES, ALPHA-KETO THIO ESTERS, ALPHA-KETO ESTERS, ALPHA-HYDROXY THIO ESTERS, AND ALPHA-HYDROXY ESTERS . CHEMISTRY OF ALPHA-KETO MERCAPTALS

A convenient synthetic conversion of β-keto sulfoxides to α-hydroxy aldehydes involves the sequence, RCOCH2-SOCH3 → RCOCH(Cl)SCH3 → RCOCH(SCH3)2 RCH(OH)CH(SCH3)2 → RCH(OH)CHO. Convenient syntheses of mandelaldehyde, atrolactaldehyde, benzilaldehyde, and 2-phenyl-2-ethylglycolaldehyde were developed. The α-chloro β-keto sulfides are readily converted to α-keto acetals. α-Keto mercaptals undergo O-alkylations and O-acylations in the presence of base. Bromination of the α-keto mercaptal followed by hydrolysis yielded S-methyl phenylthioglyoxylate (C6H5COCOSCH3). Reaction of phenylglyoxal methyl mercaptal with methanesulfenyl chloride in the presence of base yielded ω,ω,ω-tri(methylmercapto)acetophenone which can also be converted to S-methyl phenylthioglyoxalate. A convenient synthesis of S-methyl thiomandelate is described: C6H5COC(SCH3)3 → C6H5CH(OH)C(SCH3)3 → C6H5CH(OH)COSCH3. Bromination of the methyl mercaptal of phenylglyoxal in basic solution in the absence of water leads to cis- and trans-1,2-dibenzoyl-1,2-di(methylmercapto)ethylene, a product also formed in the pyrolysis of ω-chloro-ω-(methylmercapto)acetophenone. © 1969, American Chemical Society. All rights reserved.