Gold-Catalyzed Intramolecular Aminoarylation to Pyrrolidines

Based on previous work on gold-catalyzed hydroamination reactions by the same group (Angew. Chem. Int. Ed. 2010, 49, 598), the corresponding gold-catalyzed intramolecular aminoarylation reaction of N-sulfonylalkenes with boronic acids has been shown to lead to N-protected pyrrolidines and piperidines. [dppm(AuBr)2] in combination with Selectfluor® as an oxidative agent was found to catalyze the formation of pyrrolidines at room temperature in good yields while the formation of piperidines required heating at 40-60 ˚C. The reaction is proposed to proceed via a redox cycle involving the initial oxidation of gold(I) into gold(III) by Selectfluor®. Based on studies of competitive reactions using Ph-AuPPh3 and ArB(OH)2 the incorporation of the Ar moiety was demonstrated, thus suggesting that the C-C bond formation does not proceed through a reductive elimination from a phenylgold(III) species but through a bimolecular reductive elimination process.