Ru(II)Porphyrinate-based molecular nanoreactor for carbene insertion reactions and quantitative formation of rotaxanes by active-metal-template syntheses

Liniquer A Fontana,Arthur F P Alcântara,Marlon P Almeida,Marcos A Ribeiro,Vitor H Rigolin,Jackson D Megiatto,Wdeson P Barros

doi:10.1038/s41467-020-20046-x

Abstract

Selectivity in N–H and S–H carbene insertion reactions promoted by Ru(II)porphyrinates currently requires slow addition of the diazo precursor and large excess of the primary amine and thiol substrates in the reaction medium. Such conditions are necessary to avoid the undesirable carbene coupling and/or multiple carbene insertions. Here, the authors demonstrate that the synergy between the steric shielding provided by a Ru(II)porphyrinate-based macrocycle with a relatively small central cavity and the kinetic stabilization of otherwise labile coordinative bonds, warranted by formation of the mechanical bond, enables single carbene insertions to occur with quantitative efficiency and perfect selectivity even in the presence of a large excess of the diazo precursor and stoichiometric amounts of the primary amine and thiol substrates. As the Ru(II)porphyrinate-based macrocycle bears a confining nanospace and alters the product distribution of the carbene insertion reactions when compared to that of its acyclic version, the former therefore functions as a nanoreactor.

Highlights

To expand the scope of porphyrinate-based molecular capsules, incorporation of nanoreactor concepts[33] are highly desirable
The carbene transfer/insertion reactions promoted by Ru(II) porphyrinates from diazo derivatives are versatile synthetic methods as they catalyze a wide range of chemical transformations such as cyclopropanation, 1,3-dipolar cycloadditions, X–H (X = C, N, O, and S) insertions and olefination of aldehydes in the presence of phosphines[34,35,36,37,38,39,40,41,42]
The methodologies based on carbene transfer/insertion processes promoted by Ru(II) porphyrinates suffer from a serious drawback, which is the concurrent dimerization side-reaction of the carbene intermediates

Summary

Introduction

To expand the scope of porphyrinate-based molecular capsules, incorporation of nanoreactor concepts[33] are highly desirable. Selectivity to the secondary amine product is hard to achieve and requires careful control of the diazo concentration and reaction temperature as well as to use a large excess of the amine substrate (10× relative to the diazo derivative)[42] to avoid double carbenoid insertions that lead to the tertiary amine analog. It is reported the molecular design and coordinative properties of a Ru(II)porphyrinate-based molecular capsule that works as a nanoreactor. The findings reported demonstrate how the steric features of porphyrinate molecular capsules in combination with formation of mechanical bonds can be explored to change the reaction outcomes of challenging chemical transformations; the fundamental principle of nanoreactors

Methods

Results

Conclusion