Carbonyl Activation by Selenium- and Tellurium-Based Chalcogen Bonding in a Michael Addition Reaction.

Patrick Wonner,Lukas Vogel,Stefan M Huber,Tim Steinke

doi:10.1002/chem.201905057

Patrick Wonner, Lukas Vogel + Show 2 more

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https://doi.org/10.1002/chem.201905057

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Abstract

In the last years the use of chalcogen bonding—the noncovalent interaction involving electrophilic chalcogen centers—in noncovalent organocatalysis has received increased interest, particularly regarding the use of intermolecular Lewis acids. Herein, we present the first use of tellurium‐based catalysts for the activation of a carbonyl compound (and only the second such activation by chalcogen bonding in general). As benchmark reaction, the Michael‐type addition between trans‐crotonophenone and 1‐methylindole (and its derivatives) was investigated in the presence of various catalyst candidates. Whereas non‐chalcogen‐bonding reference compounds were inactive, strong rate accelerations of up to 1000 could be achieved by bidentate triazolium‐based chalcogen bond donors, with product yields of >90 % within 2 h of reaction time. Organotellurium derivatives were markedly more active than their selenium and sulphur analogues and non‐coordinating counterions like BArF 4 provide the strongest dicationic catalysts.

Highlights

In the last years the use of chalcogen bonding—the noncovalent interaction involving electrophilic chalcogen centers—in noncovalent organocatalysis has received increased interest, regarding the use of intermolecular Lewis acids
In 2017, first such cases employing neutral sulphur-based or cationic selenium-based catalysts were reported by Matile[10] and our group,[5a] with the reactions involving the reduction of quinolines and an SN1-based carbon–carbon bond formation, and similar ones were being investigated later on.[5b,11] Recently, our group could confirm the superior performance of cationic chalcogen bonding catalysts versus neutral ones in a direct comparison,[12] and we reported the first activation of a nitro group,[5c] using tellurium-based dicationic catalysts
In 2019, Wang et al described the use of bidentate selenophosphonium compounds as catalysts in a multicomponent reaction involving several carbonyl species, which likely constitutes the first activation of this functional group by chalcogen bonding.[13]

Summary

Introduction

In the last years the use of chalcogen bonding—the noncovalent interaction involving electrophilic chalcogen centers—in noncovalent organocatalysis has received increased interest, regarding the use of intermolecular Lewis acids. Even though 4I-BArF4 constitutes a relatively strong halogen bond donor, derivatives of which had been used successfully as Lewis acids before,[16] both compounds showed only little activity with less than 5 % yield of compound 3 (Table 1, entries 2 and 3).

Results

Conclusion