6533b862fe1ef96bd12c6ad6
RESEARCH PRODUCT
Diastereoselective Functionalization of a Spherand‐Type Calixarene
Volker BöhmerRalf A. JakobiErich F. PaulusPatrick O'sullivanWalter Vogtsubject
chemistry.chemical_classificationStereochemistryTrimerCrystal structureCondensation reactionMedicinal chemistryInorganic Chemistrychemistry.chemical_compoundEthyl bromoacetatePolycyclic compoundchemistryCalixareneMethyleneCyclophanedescription
Condensation of 5,5'-di-tert-butyl-2,2'-dihydroxybiphenyl (1) with formaldehyde yields a cyclic trimer 2 (and tetramer 3) having three (four) methylene groups less than a calix[6]arene (calix[8]arene). Alkylation of the (flexible) trimer with ethyl bromoacetate gives exclusively the stereoisomer 4 with C 2 symmetry, while the isomer with D 3 symmetry is not observed. Two isomers 6a and 6b (C 2 and C 1 symmetry) are obtained by treatment with tert-butyl bromoacetate which both are converted by transesterification with methanol into the same hexamethyl ester 5 having C 2 symmetry. These results are rationalized by restricted rotation around Ar-Ar bonds for larger O-alkyl groups also around Ar-CH 2 -Ar bonds. The structure of the hexaethyl ester 4 is also confirmed by single crystal X-ray analysis
| year | journal | country | edition | language |
|---|---|---|---|---|
| 1994-02-01 | Chemische Berichte |