title: Synthesis and highly selective bromination of Azacalix[4]pyrimidine macrocycles.
abstract: A number of N-substituted azacalix[4]pyrimidines were synthesized by two methods. While straightforward condensation reaction between 4,6-dichloropyrimidine and 4,6-bis(alkylamino)pyrimidines gave identically N-substituted azacalix[4]pyrimidines in low yields, a general and moderate-to-high yielding 1 + 3 macrocyclic fragment coupling reaction afforded azacalix[4]pyrimidines that contained either the same or different N-substituents. Upon treatment with N-bromosuccinimide (NBS) under controlled conditions, methylazacalix[4]pyrimidine was selectively brominated at lower rim to produce mono-, di-, and tribrominated azacalix[4]pyrimidines in good yields. While azacalix[4]pyrimidine derivatives adopted 1,3-alternate conformation in the solid state, the synthesized macrocycles were fluxional in solution, and the interconversion of various conformational structures was rapid relative to the NMR time scale.
authors.affiliation: Beijing National Laboratory for Molecular Sciences, CAS Key Laboratory of Molecular Recognition and Function, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China.
authors.forename: Li-Xia
authors.initials: LX
authors.lastname: Wang
authors.forename: De-Xian
authors.initials: DX
authors.lastname: Wang
authors.forename: Zhi-Tang
authors.initials: ZT
authors.lastname: Huang
authors.forename: Mei-Xiang
authors.initials: MX
authors.lastname: Wang
mesh_terms: D047250:Calixarenes / Q000138:chemical synthesis* / Q000737:chemistry; D002384:Catalysis; D054879:Halogenation; D047028:Macrocyclic Compounds / Q000138:chemical synthesis* / Q000737:chemistry; D008968:Molecular Conformation; D015394:Molecular Structure
chemical_list: D047028:Macrocyclic Compounds; C548254:azacalix(4)pyrimidine; D047250:Calixarenes