Alternatively compounds of formula (V) can be prepared from compounds of formula (XV) and compound of formula (XXVII) where PG is a protecting group, such as BOC. Typical conditions comprise of 1 eq of compound (XV), 1.2 eq of compound (XXVII), 1.2 eq of anhydrous cesium carbonate, 3 eq of cesium fluoride, 0.1 eq of PdCl2(dppf).CH2Cl2 in dimethylformamide as solvent at 80-100??? C. for 2-48 h.