New and efficient synthesis of solid-supported organotin reagents and their use in organic synthesis

Novel resin-bound organotin reagents have been prepared, including for the first time resin-bound dimethyl tin reagents. Mild methodology has also been developed for the very efficient synthesis of resin-bound distannanes. The resin-bound tin chloride reagents have been used in a catalytic Stille coupling cycle and the resin-bound distannanes have been used in atom transfer cyclisations and proved to be much more effective than previously described resin-bound distannanes. As expected the use of resin-bound tin reagents facilitated their easy removal at the end of the reaction, and consequently residual tin levels in the organic products were low or negligible. The resin-bound distannanes could not, however, be successfully used for the palladium catalysed stannylation of a simple aryl iodide, which would have provided a useful approach to radiolabeling of aromatic substrates. The reasons for the failure in the stannylation process is unclear but crystal structure evidence indicates that there is a hypervalent interaction between the resin-bound tin atom and an adjacent ether oxygen which may effect the reactivity of the tin intermediates in the stannylation sequence.