Ring on solid supports

An intramolecular Heck cyclization strategy was developed for the construction of indole and benzofuran rings on solid support [82], enabling rapid generation of small-molecular libraries by simultaneous parallel or combinatorial synthesis. Sn2 displacement of resin-bound y-bromocrotonyl amide 97 with o-iodophenol 96 afforded the cyclization precursor 98. A subsequent intramolecular Heck reaction using Jeffery s ligand-free conditions furnished, after double bond tautomerization, the resin-bound benzofurans, which were then cleaved with 30% TFA in CH2CI2 to deliver the desired benzofuran derivatives 99 in excellent yields and purity. 

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