Biaryl dialdehyde

An efficient atropo-enantioselective total synthesis of the axially chiral bicoumarin (+)-isokotanin was accomplished by J. Bringmann and co-workers.The key steps in this synthetic approach were the formation of a configurationally stable seven-membered biaryl lactone by the Cannizzaro reaction of the corresponding biaryl dialdehyde followed by a kinetic resolution by atroposelective ring cleavage. 

Scheme 14). Using a standard Ullmann coupling protocol, bromoaldehyde 30 was heated with activated Cu in DMF to provide the desired biaryl dialdehyde in good yields.Treatment of 29 with... 

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