Iridium porphyrin-catalysed asymmetric carbene insertion into primary N-adjacent C-H bonds with TON over 1000000.

Abstract

Selective functionalization of ubiquitous C-H bonds in organic molecules provides a straightforward and efficient approach to construct complex molecules with fewer synthetic steps and high atom economy, thus promoting more sustainable and economical chemical synthesis. A formidable challenge in the field is to increase the turnover numbers (TONs) for catalytic C-H functionalization reactions reported in the literature (generally <10,000) to reasonably high levels to reduce the cost of the reaction. Another challenge is the selective functionalization of less reactive primary C(sp³)-H bonds compared to other types of more reactive C-H bonds. We now demonstrate an efficient iridium porphyrin-catalysed asymmetric carbene insertion into primary N-adjacent C(sp³)-H bond of N-methyl indoline and N-methyl aniline derivatives. Using chiral iridium porphyrin as a catalyst, chiral β-amino acid derivatives have been obtained with very high yields and excellent ee values (up to 99%), and TONs as high as 84,000 to 1,380,000. The reaction can be readily performed on a 100 g scale while retaining its high efficiency and selectivity. We also show that this iridium catalysis can efficiently access oligomers and polymers of β-amino acid derivatives via stepwise C-H insertion, demonstrating its potential applications in materials science via C-H bond functionalization reactions.