Enhancement of alkene reactivity by a trifluoromethyl group: Synthesis of pyrrolidines via 1,3-dipolar cycloaddition
摘要:
Ethylenic compounds activated by a trifluoromethyl group undergo 1,3-dipolar cycloadditions with non-stabilized azomethine ylides to provide polysubstituted 3-trifluoromethyl-pyrrolidines in good yields, while non-fluorinated parent alkenes are in most cases unreactive in these reactions.
polar solvents the ratio of O vs. C alkylation products of ethyl 4,4,4-trifluoroacetoacetate (ETFAA)can be dependent on reaction time; in hexamethylphosphorictriamide (HMPA) or acetone, the SN2 cleavage of enol ethers of ETFAA with sodium iodide was observed with concomitant formation of the sodium enolate and the corresponding iodides, and in the case of an activated iodide the mono- and di-alkylation
CF3-Substituted alkenes have been described to be good partners in Diels-Alder reactions with the Danishefsky's diene and in 1,3-dipolar cycloadditions with nitrones and non-stabilized azomethine ylides. The influence of the CF3-group on both the activation of the double bond and the stereochemistry of the cycloaddition has been evaluated. New CF3-substituted mono- and polycyclic compounds 4 and 7, highly functionalized isoxazolidines 18, 19, 22 and 23 and pyrrolidines 12, 13 and 16 have been prepared.
BEGUE, JEAN-PIERRE;CHARPENTIER-MORIZE, MICHELINE;NEE, GERARD, J. CHEM. SOC. CHEM. COMMUN.,(1989) N, C. 83-84