Few layer 2D pnictogens catalyze the alkylation of soft nucleophiles with esters

Vicent Lloret,José Alejandro Vidal-Moya,Stefan Wild,Maria Varela,Antonio Leyva-Pérez,Sunghwan Shin,Antonio Doménech-Carbó,Gonzalo Abellán,Florian Maier,Andreas Hirsch,Frank Hauke,Miguel Ángel Rivero-Crespo,Hans-Peter Steinrück,Bettina S J Heller

doi:10.1038/s41467-018-08063-3

Abstract

Group 15 elements in zero oxidation state (P, As, Sb and Bi), also called pnictogens, are rarely used in catalysis due to the difficulties associated in preparing well–structured and stable materials. Here, we report on the synthesis of highly exfoliated, few layer 2D phosphorene and antimonene in zero oxidation state, suspended in an ionic liquid, with the native atoms ready to interact with external reagents while avoiding aerobic or aqueous decomposition pathways, and on their use as efficient catalysts for the alkylation of nucleophiles with esters. The few layer pnictogen material circumvents the extremely harsh reaction conditions associated to previous superacid–catalyzed alkylations, by enabling an alternative mechanism on surface, protected from the water and air by the ionic liquid. These 2D catalysts allow the alkylation of a variety of acid–sensitive organic molecules and giving synthetic relevancy to the use of simple esters as alkylating agents.

Highlights

Group 15 elements in zero oxidation state (P, As, Sb and Bi), called pnictogens, are rarely used in catalysis due to the difficulties associated in preparing well–structured and stable materials
Mechanistic studies unveil that the catalytic FL pnictogen selectively adsorbs the nucleophile and ester on surface, with the help of the electronic stabilization generated by the few layers underneath
Sonication of ground BP or Sb crystals dispersed in bmim-BF4 was performed in an argon-filled glovebox (

Summary

Introduction

Group 15 elements in zero oxidation state (P, As, Sb and Bi), called pnictogens, are rarely used in catalysis due to the difficulties associated in preparing well–structured and stable materials. The few layer pnictogen material circumvents the extremely harsh reaction conditions associated to previous superacid–catalyzed alkylations, by enabling an alternative mechanism on surface, protected from the water and air by the ionic liquid These 2D catalysts allow the alkylation of a variety of acid–sensitive organic molecules and giving synthetic relevancy to the use of simple esters as alkylating agents. We show the synthesis of two different exfoliated, few layer 2D pnictogens, phosphorene (few-layer black phosphorous (FLBP)) and antimonene (FL-Sb), and their use as catalysts in the alkylation of alcohols, thiols, and indoles with simple esters, in good yields and with excellent selectivity To our knowledge, this is the first organic reaction catalyzed by pristine 2D-pnictogens reported so far. FL-Sb exhibits a better performance than FL-BP, in accordance with its higher polarizability, enabling acid-sensitive aromatic derivatives to be selectively alkylated with simple esters

Methods

Results

Conclusion