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24.2.9.1.23 Method 23: Synthesis from Ketene S,S-Acetals

DOI: 10.1055/sos-SD-024-00398

Kantlehner, W.Science of Synthesis, (200624358.

In general it is not possible to transform ketene S,S-acetals directly into ketene O,N-acetals. The reactions of ketene S,S-acetals with amino alcohols are exceptions, as cyclic ketene O,N-acetals, e.g. 26, are formed (Scheme 40). Examples include 2-aminoethanol,[‌62‌‌67‌] 2-aminophenol,[‌14‌,‌62‌‌65‌,‌68‌] 2-amino-5-nitrophenol,[‌62‌,‌64‌] 3-aminopropan-2-ol,[‌66‌] 2-aminopropan-1-ol,[‌69‌] 3-aminopropan-1-ol,[‌70‌] 2-amino-2-methylpropan-1-ol,[‌71‌] 3-amino-2,2-dimethylpropan-1-ol,[‌71‌] 2-amino-1-phenylpropan-1-ol,[‌72‌] 2-aminobutan-1-ol,[‌73‌] and amino polyols.[‌74‌] A comprehensive listing of the ketene O,N-acetals prepared from these amino alcohols has been published.[‌75‌] Cyclic ketene O,N-acetals have also been prepared from ketene S,S-acetals and serine esters (Scheme 40).[‌76‌] This ketene O,N-acetal synthesis has found application in carbohydrate[‌77‌,‌78‌] and steroid chemistry.[‌79‌]

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