4-Acetylamino-2,2,6,6-tetramethyl-piperidine

The olefin metathesis of 3-hydroxy-4-vinyl-l,2,5-thiadiazole 112 and a McMurry coupling reaction (Ti3+ under reductive conditions) of the aldehyde 114 were both unsuccessful <2004TL5441>. An alternative approach via a Wittig reaction was successful. With the use of the mild heterogenous oxidant 4-acetylamino-2,2,6,6-tetramethyl-piperidine-l-oxoammonium perfluoroborate (Bobbitt s reagent), the alcohol 113 was converted into the aldehyde 114. The phosphonium salt 115 also obtained from the alcohol 113 was treated with the aldehyde 114 to give the symmetrical alkene 116 (Scheme 16) <2004TL5441>. 

Conversion of substituted benzoins to corresponding benzils occurs in quantitative yield when ZnO—DABCO eomplex is used to catalyse aerobic oxidation by O2 in toluene in the presence of K2CO3. The use of chiral ligand (118), in the presence of ZnS04 7H20 and 4-acetylamino-2,2,6,6-tetramethyl-piperidine-l-oxoammonium perchlorate (TEMPO), resulted in isolation of benzil along with enantiomerically enriched benzoin (43% ee). ... 

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