Efficient Multicomponent Active Template Synthesis of Catenanes.

James E M Lewis,Stephen M Goldup,Florian Modicom

doi:10.1021/jacs.8b01602

James E M Lewis, Stephen M Goldup + Show 1 more

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https://doi.org/10.1021/jacs.8b01602

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Abstract

We describe a simple and high yielding active template synthesis of [2]catenanes. In addition to mechanical bond formation using a single premacrocycle bearing an azide and alkyne moiety, our method is also suitable for the co-macrocyclization of readily available bis-alkyne and bis-azide comonomers and even short alkyne/azide components which oligomerize prior to mechanical bond formation.

Highlights

Many of the seminal contributions1 to the synthesis of mechanically interlocked molecules2 focus on catenanes,3 reports of rotaxanes have grown to dominate the field,2i in part due to the potential for shuttling motions in rotaxanes that makes them attractive for the development of molecular machines.4,5 the higher synthetic challenge involved in catenane synthesis probably plays a role; whereas rotaxanes can be synthesized readily using threading-thenstoppering methodologies, catenane synthesis requires a macrocyclization event to capture the interlocked architecture with the attendant competition between cyclization and oligomerization
Reactions that allow the assembly of the new macrocycle from small building blocks such as Stoddart’s donor−acceptor6 and pimer7 systems, and the amide-templated examples developed by Vögtle, Hunter and Leigh are attractive due to their synthetic efficiency
The active template (AT) approach to rotaxanes10 has the potential to overcome many of the outstanding challenges in catenane synthesis as AT-reactions typically proceed in high yield and are extremely general with respect to the substrates employed, including sterically hindered examples

Summary

Introduction

Many of the seminal contributions1 to the synthesis of mechanically interlocked molecules2 focus on catenanes,3 reports of rotaxanes have grown to dominate the field,2i in part due to the potential for shuttling motions in rotaxanes that makes them attractive for the development of molecular machines.4,5 the higher synthetic challenge involved in catenane synthesis probably plays a role; whereas rotaxanes can be synthesized readily using threading-thenstoppering methodologies, catenane synthesis requires a macrocyclization event to capture the interlocked architecture with the attendant competition between cyclization and oligomerization. Macrocycle 2c required modification of the conditions to overcome a slower reaction and diminished selectivity for the catenane compared with 2a; addition of 1.5 equiv of 1 to 2c at 80 °C allowed quantitative consumption of 2c and isolation of [2]catenane 3c in 98% yield (entry 3).

Results

Conclusion