4.1.13  General method D for the synthesis of compounds 23, 24 and 25
To a solution of 20 in anhydrous NMP (conc. 0.03 M) was added the corresponding bromide reagent (3.00 eq) and DIEA (3.00 eq). After stirring for 4 h at 110 °C under microwaves, the reaction mixture was diluted with AcOEt and brine. The aqueous layer was extracted with AcOEt and the combined organic extracts were washed with brine, dried over Na2SO4 and concentrated under vacuum. The residue was purified by flash column chromatography (silica gel, linear gradient 0–4% MeOH in DCM) to give the desired compound as a colorless solid.