Jeffrey L. Katz and colleagues, Colby College, Maine, USA, report the first single-step, regioselective synthesis of diazadioxacalix[4]arenes and diazadioxa[1₄]cyclophanes with alternating N/O-bridge patterns. The macrocycles are formed regioselectively by condensation of 3- or 4-amino-phenols with 1,5-difluoro-2,4-dinitrobenzene.
The obtained bridge-pattern selectivity greatly facilitates the regioselective formation of asymmetrically functionalized macrocycles.

Investigations into the rates of conformational interconversion of the described macrocycles, further mechanistic details of their synthesis, and resolution of enantiomers, are ongoing and will be reported in due course.

• Single-Step, Regioselective Synthesis of Diazadioxacalix[4]arenes and Diazadioxa[14]cyclophanes Bearing an Alternating N/O-Bridge Pattern,
  Nicholas P. Bizier, Jack P. Vernamonti, Jeffrey L. Katz,
  Eur. J. Org. Chem. 2012.
  DOI: 10.1002/ejoc.201200137