5-(Trimethylstannyl)-2H-pyran-2-one and 3-(trimethylstannyl)-2H-pyran-2-one: New 2H-pyran-2-one synthons

5-(Trimethylstannyl)-2H-pyran-2-one (11) and 3-(trimethylstannyl)-2H-pyran-2-one (30), readily prepared from the corresponding bromo-2H-pyran-2-ones, undergo Pd(0)-catalyzed coupling reactions with a variety of enol triflates to give 5- and 3- substituted 2H-pyran-2-ones, respectively, This reaction is applicable to the enol triflates of 14 beta-hydroxy-17-ketosteroids, and therefore may prove useful in convergent syntheses of lucibufagins and bufadienolides.