Berbine derivatives, synthesis

Pd(OAc)2] in the presence of PPh3 was used as catalyst. The use of vinyl bromides in lactam formation has also been reported.498 Imides were obtained from aryl bromides. The method has further been applied to the synthesis of diazepam and 1,4-benzodiazepines499 and to a-methylene lactams and lactones.S00 501 In connection with the synthesis of natural products, the reaction has been employed in the preparation of hexadehydrohimbane,502 anthramycin503 and berbine derivatives.504 The catalyst was prepared in situ from [Pd(OAc)2] (106) and PPh3 in all cases. The mechanism of lactam formation is analogous to that for amides (Scheme 42). 

The arylenamide photocyclisation protocol continues to provide convenient access to intermediates of interest in alkaloid synthesis. Spirocyclic 5-lactam (55) has been prepared from cycloalkylenamide (54) and irradiation of enones (56) yields the corresponding spiroketones (57). Analogous photocyclisations have led to nitro-substituted berbine derivatives. The piperidine arylenamides (59) are efficiently photocyclised to the corresponding benzo[b]quinolizine-6-ones (60), providing convenient access to benzoquinolizidine derivatives. In contrast,... 

Brown etal. reported the synthesis of many berbine derivatives, isopavine alkaloids, and amurensinine (56f) (581, 629). They describe some rearrangements of those alkaloids. 3-Hydroxy-2-methoxy-9,10-methylene-dioxyberbine (59d) and 3-hydroxy-2-methoxy-10,ll-methylenedioxy-berbine (60h) were synthesized through the N-formyl derivatives of... 

A very common method for the synthesis of berbine alkaloids is based on the one-pot double cyclization of iV-(phenylethyl)benzeneacetamide derivatives (e.g. 305) in the presence of phosphorus pentachloride or phosphorus oxychloride (Scheme 67) <81H(16)449,81S818,85AP(318)168,85IJC(B)360>. 

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