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  • Title: Synthesis and highly selective bromination of Azacalix[4]pyrimidine macrocycles.
    Author: Wang LX, Wang DX, Huang ZT, Wang MX.
    Journal: J Org Chem; 2010 Feb 05; 75(3):741-7. PubMed ID: 20043627.
    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.
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