Active template synthesis.

Area of Science:

• Supramolecular Chemistry
• Organic Synthesis
• Materials Science

Background:

• Active template synthesis utilizes structural elements (metals or functional groups) as both templates and catalysts.
• This approach facilitates covalent bond formation for constructing mechanically interlocked molecular architectures.
• It differs from passive templating by enabling traceless synthesis, ideal for molecules without strong intercomponent binding.

Purpose of the Study:

• To review the concept, advantages, and limitations of active template synthesis for interlocked molecules.
• To chart the diverse reactions employed in active template synthesis.
• To discuss applications in molecular machinery, catalysis, and materials science.

Main Methods:

• Metal-ion-mediated synthesis, notably using copper(I)-catalyzed alkyne-azide cycloaddition (CuAAC).
• Metal-free active template synthesis, leveraging crown ether cavities to accelerate reactions.
• Kinetic control to capture interlocked structures from transiently assembled intermediates.

Main Results:

• Successful synthesis of various rotaxanes, catenanes, and knots since 2006.
• Demonstration of traceless synthesis for mechanically interlocked molecules.
• Metal-free methods enable rotaxane synthesis without recognition elements, including molecular pumps and superbases.

Conclusions:

• Active template synthesis is a versatile strategy for constructing complex mechanically interlocked molecular architectures.
• The method offers advantages in traceless synthesis and constructing molecules with minimal intercomponent interactions.
• It has broad applicability in advanced fields like molecular machinery and materials science.