RESUMEN
Herein, attempted oxidation of selected allenols with PCC affording α'-hydroxydienones rather than simple oxidation products is described. The formation of the products observed is rationalized via a series of sigmatropic shifts, followed by hydrolysis.
RESUMEN
Trifluoromethyl-substituted superelectrophiles were generated in superacid (CF(3)SO(3)H), and their chemistry was examined. The strong electron-withdrawing properties of the trifluoromethyl group are found to enhance the electrophilic character at cationic sites in superelectrophiles. This leads to greater positive-charge delocalization in the superelectrophiles. These effects are manifested by the unusual chemo-, regio-, and stereoselectivities shown by the superelectrophiles in chemical reactions.
Asunto(s)
Fluoroacetatos , Piridinas/química , Mesilatos/química , Piridinas/síntesis química , Ácido Trifluoroacético/químicaRESUMEN
Treatment of 2-tosyloxycyclopentanone with substituted furans in the presence of a chiral amino alcohol catalyst and K2HPO4 results in the formation of (4 + 3) cycloaddition products with enantioselectivities that exceed 90% in certain cases.
RESUMEN
A 3-phenylsulfanyl-substituted allylic alcohol and an ester thereof were treated with Brønsted acids or a gold catalyst, respectively, to generate vinylthionium ions. These species react with dienes, primarily substituted furans, to give products of either (4 + 3)-cycloaddition or Friedel-Crafts alkylation. The results are rationalized on the basis of a stepwise mechanism in which the relative rates of ring closure versus proton loss in the intermediate σ-complex determine the course of the reaction.