Sulfoxides, 3-keto Pummerer rearrangement

Among other electrophilic reagents ctq>able of twinging about the Pummerer rearrangement are halides of organic and inorganic acids. As these halides transform sulfoxides into a-chlorosulfides they complement the sulfide chlorination route to these compounds. Thionyl chloride reacts readily with sulfoxides and 3-keto sulfoxides methyl phenyl sulfoxide furnishes chloromethyl phenyl sulfide (equation 37). Benzoyl chloride and acetyl chloride behave similarly. d yanuric chloii is transformed into cyanuric acid by dimethyl sulfoxide, which in turn is transformed into methyl chloromethyl sulfide (equation 3g).54,S5... 

Synthesis of P-Keto Sulfoxides. Optically active p-keto sulfoxides are very useful building blocks (eq 4) because they can be stereoselectively reduced to afford either diastereomer of the corresponding p-hydroxy sulfoxide under appropriate conditions (Diisobutylaluminum Hydride or Zinc ChloridefDlBALf and thus give access to a wide variety of compounds chiral carbinols by desulfurization with Raney Nickel or LithiumJethyhmme ini the case of allylic alcohols epoxides via cyclization of the derived sulfonium salt butenolides by alkylation of the hydroxy sulfoxide 1,2-diols via a Pummerer rearrangement followed by reduction of the intermediate. ... 

Stream of nitrogen. The initial product, the jS-keto sulfoxide II, undergoes intramolecular ester condensation with formation of the 1,3-indanedione system. Ill, which in the presence of hydrochloric acid undergoes Pummerer rearrangement to 2-chloro-2-methylmercapto-l,3-indanedione (IV). This crystalline product (m.p. 63°) is obtained in yield of 80% and is hydrolyzed in boiling water nearly quantitively to ninhydrin (V). 

Pummerer rearrangement (5,3-4). The Pummerer rearrangement of P-hydroxy sulfoxides to derivatives of a-hydroxy aldehydes has been extended to the rearrangement of 3-keto sulfoxides. Thus rearrangement of (1) with acetic anhydride-sodium acetate in toluene under reflux gives the S-aryl thioester (2) in 74% yield. The ester is hydrolyzed by base to mandelic acid (3). In the absence of sodium acetate the normal product of the Pummerer rearrangement... 

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