Cyclo-pentanone, substituted

Cyclic ketones react faster than the aliphatic ketones in the order cyclo-pentanone > cyclohexanone > higher-membered cyclic ketones. a-Substi-tuted ketones give the less substituted enamines, which in turn could be alkylated to put a substituent on this position of the ketone [51] (Eq. 11). 

Similar arguments apply to many alicyclic ketones the substituted carbon of the ring of 2-substituted cyclohexanones and cyclo-pentanones showed the major ability to migrate to nitrogen (reaction... 

The reaction of monooxo C-H acids such as acetone/ ethyl methyl ketone,or cyclo-pentanone with monocyclic A, 0-acetals or bicyclic A, 0-acetals or aminals gave the expected substitution products 1. Aqueous buffer solutions of pH 5.5 were reported to be sufficient for activation of bicyclic aminal precursors. Monocyclic aminal or hemiaminal starting materials were less reactive. Remarkably, methyl cyanoacetate could not be aminocyclopropylated. The sterical course of the reaction of bicyclic derivatives was not determined. 

The reaction can also be extended to quatemized benzyl Meldrum acids 24, affording products 25 with a different substitution on the cyclo-pentanone ring (Table 3.10). The method is also applied to the synthesis of... 

Methods for derivatization of aldehydes and ketones using preformed Mannich reagents have been summarized.2-(Morpholinothio)benzothiazole (55) is a key reagent in a synthesis of 2-substituted cyclopentenones from the cyclo-pentanone (Scheme 47). 

Similarly Ni catalysts are useful substitutes to Pd for the selective olefin reduction in an a,/8-unsaturated ketone. Finely divided Ni (and partially deactivated by washing it with a 0.1% MeOH solution of acetic acid) in a mixture 5% HCCl3/EtOH is efficient at RT and atm P. Neutral catalysts, U—Ni—N, obtained by refluxing precipitated Ni with isopropanol, also shows selectivity, mesityl oxide being reduced to methyl-1 pentanone-2 . 4-Cyclopentene-l,3-dione, 5, can be converted into 1,3-cyclo-pentanedione, 6, by hydrogenation over partially deactivated neutral Ni catalyst ... 

---