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Intra‐ und extraannular funktionalisierte helical‐chirale [2.2]Metacyclophane: Synthese, Circulardichroismus und Struktur‐Chiroptik‐Beziehungen
Author(s) -
Vögtle Fritz,
Knops Peter,
Ostrowicki Andreas
Publication year - 1990
Publication title -
chemische berichte
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 0009-2940
DOI - 10.1002/cber.19901230918
Subject(s) - chemistry , racemization , bathochromic shift , enantiomer , circular dichroism , meso compound , stereochemistry , chiral column chromatography , crystallography , fluorescence , physics , quantum mechanics
Intra‐ und Extraannularly Functionalized Chiral [2.2]Metacyclophanes: Synthesis, Circular Dichroism, and Structure ‐ Chiroptic Relationships A simple one‐step cyclization reaction for the synthesis of the title compounds 1 ‐ 5 is presented; separation (enrichment) of enantiomers is achieved by HPLC mainly on (+)‐PTrMA. The kinetics of interconversion (racemization) of the new dihetera[2.2]metacyclophanes are determined: No racemization of the internally substituted phanes is found on heating until decomposition, whereas the extraannularly substituted compounds exhibit barriers of interconversion of about 130 kJ/mol, similar to that of the unfunctionalized skeleton 1a . For the pyridinophane 2 the barrier (110 kJ/mol) is lower corresponding to the decreased spatial requirement of the nitrogen lone pair compared to a C‐H bond. The circular dichroism curves of the intraannularly functionalized phanes are compared with those of the extraannularly functionalized reference compounds: A bathochromic shift of the Cotton effect at short wavelengths is found, which is increasing with the bulkiness of the internal functional group.