Buchwald-Hartwig coupling palladium® acetate

Clausine V (151) was prepared in two steps (Scheme 32) [150]. Buchwald-Hartwig coupling of /n-anisidine (113) with 3-bromoanisole afforded the diaryla-mine 150. Different reaction conditions have been tried for the subsequent palladium(ll)-catalyzed oxidative cychzation to clausine V (151) (Table 3). Application of 0.1 equiv. of palladium(ll) acetate and 0.1 equiv. of copper(ll) acetate in glacial acetic acid under an oxygen atmosphere gave the best result for the catalytic process (49% yield). The turnover number of almost 5 confirmed that the system works in a catalytic mode. However, in this case the best yield (67%) was obtained using stoichiometric amounts of palladium(ll) acetate in air without co-oxidant. 

Buchwald-Hartwig amination of iodobenzene 92 with 2-benzyloxy-4-methyl-aniline 93 affords the diarylamine 94 in high yield (Scheme 32). In this case the Goldberg coupling gives poor yields. Oxidative cyclization of compound 94 using stoichiometric amounts of palladium(II) acetate in acetic acid under reflux leads to the carbazole 95, which by reductive debenzylation provides... 

The second coupling component, 6-aminocarbazole 1082, was prepared starting from the same known O-tosylate 1063 (165,665). Thus, Buchwald-Hartwig palladium-catalyzed amination of 4-bromonitrobenzene (1076) with 1063 afforded the diaryla-mine 1077. Treatment of 1077 with an excess of Pd(OAc)2 in acetic acid led to the carbazole 1078 in 53% yield. After protection of the carbazole nitrogen with a 2-trimethylsilylethoxymethyl (SEM) group, the product 1079 was subjected to alkaline... 

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