Calix[4]arenes with two different chemical modifications at the bridges

Hexabromocalix[4]arene derivatives (3a and 3b) possessing pairs of dibromomethylene and bromomethylene groups located at distal or proximal positions of the calix scaffold were prepared via photochemical bromination of tetramethoxycalix[4]arene. The dibromomethylene groups undergo hydrolysis to afford calix[4]arenes possessing pairs of carbonyl groups and bromomethylene groups located at distal or proximal bridges (4a and 4b, respectively). The bromomethylene groups of 4 undergo reactions with nucleophiles under S _N1 conditions to afford a wide array of derivatives possessing two different chemical modifications at the bridges.