Synthesis of antibiotics WS 5995 A and C and related compounds by palladium-catalyzed coupling of 2-bromonaphthoquinones with organostannanes

Article abstract of DOI:10.1021/jo00099a045

The synthesis of arylnaphthoquinones can be performed simply by using as the key reaction the Pd(0)- and Cu(I)-catalyzed coupling of arylstannanes with 2-bromonaphthoquinones as the electrophiles. The palladium-catalyzed coupling reaction is general and allows for the functionalization of the unprotected quinone nucleus with alkyl, alkenyl, and aryl substituents. The coupling process tolerates the presence of a chelated peri hydroxyl and steric crowding of a 2,6-disubstituted arylstannane, although the preparation of a 2,6,2',6'-tetrasubstituted biaryl by coupling of 2-bromo-3,5-bis(acetyloxy)-1,4-naphthoquinone as the electrophile with 2,6-disubstituted arylstannanes was unsuccessful. The syntheses of quinonoid antibiotics WS 5995 A and C was accomplished by using this method as the key step. Benz[b]phenanthridinone 1, hypothetical intermediate in the biosynthesis of benz[b]phenanthridine alkaloids, was also prepared from antibiotic WS 5995 C or by addition of ammonia to the 2-aryl-1,4-naphthoquinone 41 followed by heterocyclization.