Designing large triangular chiral macrocycles: efficient

Area of Science:

• Supramolecular Chemistry
• Organic Synthesis
• Crystal Engineering

Background:

• Macrocyclic chemistry involves the synthesis and study of large ring structures.
• Hexaiminomacrocycles are a class of compounds with potential applications in host-guest chemistry and materials science.
• Understanding the relationship between molecular structure, symmetry, and conformational constraints is crucial for designing new macrocyclic compounds.

Purpose of the Study:

• To synthesize novel triangular 30- and 27-membered hexaiminomacrocycles.
• To investigate the reaction mechanism and conformational aspects governing macrocyclization.
• To characterize the synthesized macrocycles using X-ray crystallography and prepare their reduced derivatives.

Main Methods:

• [3 + 3] cyclocondensation reaction between (R,R)-1,2-diaminocyclohexane and terephthalaldehyde/isophthalaldehyde.
• Molecular modeling to study conformational constraints and reaction pathways.
• X-ray crystallographic analysis of the synthesized macrocycles.
• Sodium borohydride reduction to obtain cyclic hexaamines.

Main Results:

• Successful synthesis of triangular 30- and 27-membered hexaiminomacrocycles (4 and 5) with D(3) and C(3) symmetry, respectively.
• Molecular modeling indicated that conformational constraints dictate the macrocyclization process.
• X-ray analysis of cocrystal 4.AcOEt showed deviations from ideal D(3) symmetry due to the crystal environment.
• Preparation of reduced cyclic hexaamines (6 and 7) via sodium borohydride reduction.

Conclusions:

• The [3 + 3] cyclocondensation provides an efficient route to triangular hexaiminomacrocycles.
• Conformational factors play a significant role in the formation of these macrocyclic structures.
• Crystal packing forces can influence the observed symmetry of macrocycles in the solid state.
• The synthesized macrocycles can be readily reduced to corresponding cyclic hexaamines.