New chemoselective metalating agents for solid-phase synthesis

Development of new soluble, chemoselective metalating reagents is essential for exploring solid-phase organometallic chemistry. Cuprates and zincates were expected to be potentially usable for solid-phase chemistry, and, we s tarted to investigate chemoselective solid-phase halogen-metal exchange rea ctions using ate complexes. At 0 degrees C, the halogen-zinc exchange react ions proceeded smoothly in the presence of 2.2 equiv of LTBZ, and the subse quent reaction with an electrophile followed by cleavage with NaOMe/MeOH-TH F gave the desired product in an excellent yield. The immobilized organozin cate on polymer support was also transformed into the immobilized organocup rate by treatment with lithium cyanothienylcuprate. The palladium-catalyzed cross-coupling reaction of the immobilized organozincate with iodobenzene proceeded smoothly at room temperature to give an unsymmetrical biaryl. Thi s methodology is considered to provide a new chemoselective method for soli d-phase carbon-carbon bond formation.