A highly efficient methodology for the preparation of N-methoxycarbazoles and the total synthesis of 3,3''''-oxybis(methylene)bis(9-methoxy-9H-carbazole)

摘要

A convenient and highly efficient method is described for the synthesis of N-methoxycarbazole derivatives,including those with sterically demanding,benzannulated,or strongly electron-donating or-withdrawing substituents.Various N-methoxycarbazole derivatives were directly prepared in good-to-moderate yields by the Pd_(2)(dba)_(3)CHCl_(3)/9,9-dimethyl-4,5-bis(diphenylphosphino)xanthene-catalyzed reactions of the corresponding dibromobiphenyl compounds and methoxyamine.Based on this methodology,the first total synthesis of 3,3′-[oxybis(methylene)]bis(9-methoxy-9H-carbazole),an antimicrobial dimeric carbazole alkaloid previously isolated from the stem bark of Murraya koenigii,was achieved in 18% yield over seven steps from 1,2-dibromobenzene.