Fast and selective organocatalytic ring-opening polymerization by fluorinated alcohol without a cocatalyst

Wei Zhao,Ji Li,Nikos Hadjichristidis,Yanfeng Lv,Zihao Feng,Yonghao Ni

doi:10.1038/s41467-019-11524-y

Abstract

Organocatalysis is an important branch of catalysis for various organic transformations and materials preparation. Polymerizations promoted by organic catalysts can produce polymeric materials without any metallic residues, providing charming materials for high-value and sensitive domains such as biomedical applications, microelectronic devices and food packaging. Herein, we describe a fluorinated alcohol based catalytic system for polypeptide synthesis via catalytic ring-opening polymerization (ROP) of α-amino acid N-carboxyanhydride (NCA), fulfilling cocatalyst free, metal free, high rate and high selectivity. During polymerization, the fluorinated alcohol catalyst forms multiple dynamic hydrogen bonds with the initiator, monomer and propagating polymer chain. These cooperative hydrogen bonding interactions activate the NCA monomers and simultaneously protect the overactive initiator/propagating polymer chain-ends, which offers the whole polymerization with high activity and selectivity. Mechanistic studies indicate a monocomponent-multifunctional catalytic mode of fluorinated alcohol. This finding provides a metal free and fast approach to access well-defined polypeptides.

Highlights

Organocatalysis is an important branch of catalysis for various organic transformations and materials preparation
As an elegant alternative to organometallic and enzymatic catalysis, hydrogen-bonding organocatalysis has been a promising pathway for innovative polymer synthesis, especially for the preparation of metal-free polymers required for advanced packaging, medical and microelectronic applications[37,38,39,40,41,42]
Methodology of fluorinated alcohols and provides a pathway for polypeptides synthesis, fulfilling metal free, high activity, and high selectivity. Other merits of this strategy are: (1) the 1,3-BisHFAB catalyst and the aminoalcohol initiator used in this study are all commercially available organic chemicals, (2) the catalyst can be removed from final polypeptide after polymerization, which provides a facile way to get clean polypeptides for researchers who focus on the functions and applications of polypeptides but have backgrounds other than organic chemistry

Summary

Introduction

Organocatalysis is an important branch of catalysis for various organic transformations and materials preparation. Without (−)-sparteine, the polymerization cannot happen (Fig. 1a)[66] To the best of our knowledge, so far there has been no report of utilizing a fluorinated alcohol as a catalyst for polymerization in the absence of base cocatalyst In this contribution, we show that 1,3-bis(2-hydroxyhexafluoroisopropyl)benzene (1,3-Bis-HFAB), a small fluorinated alcohol, without the assistance of a Lewis base cocatalyst, can catalyze a fast and selective ROP of α-amino acid N-carboxyanhydride (NCA), resulting in well-defined polypeptides. These cooperative hydrogen-bonding interactions activate the monomer and simultaneously protect the overactive initiator/polymer chain from side reactions, offering high reaction rates and selectivity in the polymerization (Fig. 2) This finding represents a nonconventional catalysis a 1,3-Bis-HFAB (catalyst)

Methods

Results

Conclusion