Facile synthesis of silylated 4,5-disubstituted phthalates via inverse electron-demand cycloaddition of 2-pyrone-4,5-dicarboxylate with silylacetylenes
A facile and efficient synthesis of silylated 4,5-disubstituted phthalates through the inverse electron-demand [4+2] cycloaddition of 2-pyrone-4,5-dicarboxylate with various silylacety-lenes has been developed. The reaction was promoted by 4A molecular sieves (MS 4A) to afford the corresponding polysubstituted arenes with functionalizable silyl groups in good to high yield, thus providing versatile access to a wide variety of functionalized phthalates that represent promising intermediates for the synthesis of fine chemicals, particularly photochemically active compounds.
Synthesis of 2-Oxo-2H-pyran-5-carboxylate Derivatives
3-Substituted diethyl pent-2-enedioates are easily formylated by means of ethyl formate/TiCl4/4-methylmorpholine to produce the ethoxymethylene derivatives, which are smoothly cyclized either with HCOOH or PPA to the corresponding 2-oxo-2H-pyran-5-carboxylate derivatives.
Kvita, Vratislav
p. 411 - 416
(2007/10/02)
Alkynes from 5-Aminoisoxazoles
Diazotization of 5-aminoisoxazoles that bear at least one electron-withdrawing group by reaction with sodium nitrite in AcOH-H2O affords substituted acetylenes.A reaction path is proposed.