Rhodium‐Catalyzed Asymmetric Macrocyclization towards Crown Ethers Using Hydroamination of Bis(allenes)

Abstract

Crown ethers (CE) are indispensable building blocks in supramolecular chemistry, coordination chemistry, catalysis and material science. Enantiomerically enriched CEs exhibit strong asymmetric induction in phase transfer catalysis, supramolecular catalysis and molecular recognition processes. Traditional methods (using chiral substrates) have often been used to access these valuable compounds, which limit their diversity and consequently their applicability. Thus, notwithstanding the ubiquitous applications of chiral CEs, their catalytic and stereoselective synthesis has remained basically unexplored. Herein, a practical catalytic method is described for the gram scale synthesis of a class of chiral CEs (aza‐crown ethers; ACEs) using rhodium‐catalyzed hydroamination of bis(allenes) with diamines. This diversity oriented synthetic approach furnishes vinyl functionalized ACEs in high yields and enantioselectivity. Using this approach, a wide range of chiral crown ethers with ring sizes ranging from 12 to 36 have been successfully prepared in high yields of up to 92%, dr of up to >20:1 and er of up to >99:1.These vinyl substituted CEs allow for further diversification giving facile access to various CE derivatives as well as to their three‐dimensional analogues using ring‐closing metathesis. Some of these chiral CEs themselves display high potential for use in asymmetric catalysis.