Macrocycles bisaryl ether

Many other reactions have been used to construct macrocycles, and many are related to specific bond formations and therefore not very widely applicable. Since bisaryl ethers and biphenyl units are relatively common in naturally occurring macrocycles [4] (both units can be found in the important antibiotic vancomycin, 20, Fig. 7), some approaches to their synthesis will... 

Having stitched together the four aryl building blocks, all that essentially remained from 37 to complete the AB/C-O-D fragment were two macrocyclization events. The first of these closures, the formation of the C-O-D bisaryl ether system, was mildly effeeted through treatment of this compound with CuBr Me2S and K2CO3 in a mixture of pyridine and MeCN at 82 °C. Unfortunately, this macrocyclization failed to afford any atropselectivity in that both 36 and 84 were obtained in a 1 1 ratio in 67 % combined yield. 

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