Synthesis of Highly Functionalized Biaryls by Condensation of 2-Fluoro-1,3-bis(silyloxy) 1,3-Dienes with 3-Cyanochromones and Subsequent Domino “Retro-Michael/Aldol/Fragmentation”
The Me3SiOTf-mediated condensation of 1-ethoxy-2-fluoro-1,3-bis(trimethylsilyloxy) 1,3-dienes with 3-cyanochromones afforded 3-cyano-2-(4-ethoxy-3-fluoro-2,4-dioxobutyl)-chroman-4-ones. Their reaction with triethylamine afforded fluorinated azaxanthones or biaryls. The product distribution depends on the structure of the diene. The formation of the biaryls can be explained by an unprecedented domino "retro-Michael/aldol/fragmentation" reaction.
Nucleophilic fluorination of β-ketoester derivatives with HBF4
作者:Raffaele Pasceri、Hannah E. Bartrum、Christopher J. Hayes、Christopher J. Moody
DOI:10.1039/c2cc37284c
日期:——
Treating readily available α-diazo-β-ketoesters with HBF4 results in nucleophilic fluorination by the usually inert and stable tetrafluoroborate anion. The resulting α-fluoro-β-ketoesters are highly versatile synthetic intermediates, for example in the preparation of fluoro-heterocycles, as illustrated by the direct formation of fluoro-pyrimidines, -pyrazoles and -coumarins in a single step.