Intramolecular aryl transfer to thionium ions in an approach to alpha-arylacetamides.

An intramolecular aryl transfer to thionium ions has been exploited in a fluorous synthesis of alpha-arylacetamides.

A dearomatizing, thionium ion cyclization for the synthesis of functionalized, azaspirocyclic cyclohexadienones.

Thionium ions, generated by the addition of thiols to N-benzylglyoxamides, undergo a dearomatizing spirocyclization. The alkyl or arylsulfanyl group introduced during the thionium ion cyclization can act as a synthetic handle and a stereochemical control element during modifications of the azaspirocyclic frameworks (R(F) = CH(2)CH(2)C(8)F(17)).

Highly stereoselective oxy-michael additions to beta,gamma-unsaturated alpha-keto esters: rapid enantioselective synthesis of 3-hydroxybutenolides.

The highly diastereoselective oxy-Michael addition of the "naked" anion of (6S)-methyl delta-lactol to gamma-substituted beta,gamma-unsaturated alpha-keto esters leading to the direct formation of THP*-protected gamma-hydroxy alpha-keto ester derivatives is described. Subsequent acid-mediated deprotection affords the 3-hydroxybutenolides in high yields.

Unusual retention behaviour of 4-substituted piperidines on polybutadiene and polystyrene coated zirconia by comparison to reverse phase silica.

The retention properties of a range of N-methylated and N-des-methyl 4-substituted piperidines on polybutadiene (PBD) and polystyrene (PS) coated zirconia have been studied and compared to those of Xterra RP(18) and Genesis C(18) silica. The effect of buffer type and pH are investigated with regard to the elution order on all three stationary phases. The change in the elution order is linked to the degree of substitution of the piperidine nitrogen and appears to be independent of the rest of the structure, indicating that this moiety is most heavily involved in the separation mechanism on the zirconia phases.