64939-64-6Relevant articles and documents
Activation of iodosobenzene by catalytic tetrabutylammonium iodide and its application in the oxidation of some isoquinoline alkaloids
Huang, Wei-Jan,Singh, Om V.,Chen, Chung-Hsiung,Chiou, Sheng-You,Lee, Shoei-Sheng
, p. 1069 - 1078 (2007/10/03)
Oxidation of N-methyltetrahydroisoquinolines with iodosylbenzene in the presence of a catalytic amount of tetrabutylammonium iodide in various solvents afforded N-methyl-2H-3,4-dihydroisoquinol-1-ones in almost quantitative yields. The application of this finding to the oxidation of other isoquinolines, including tetrahydroisoquinolines, lycorine diacetate, and benzyltetrahydroisoquinolines, also afforded the corresponding lactams in good yields, however, accompanied by a few minor byproducts. Under similar conditions, tetrahydroberberine gave a rearranged compound, berberal, as the major product, accompanied by 8-oxoberberine and berberine.
Reaction of Protoberberine-type Alkaloids. Part 12. A Facile Method for Regiospecific Oxygenation and Excited Oxidative Ring-cleavage of Berberine Alkaloids
Kondo, Yoshikazu,Imai, Jiro,Inoue, Hideo
, p. 911 - 918 (2007/10/02)
Regiospecific photo-oxygenation and photo-oxidative ring-cleavage of protoberberine alkaloids is described.Irradiation of a solution of dihydroberberine (1) in the presence of Rose Bengal under aerated conditions gave 13-oxidoberberine (3) along with berberine (2) in 80 and 7percent yields, respectively.In contrast, 7,8-dihydrocoralyne (5) gave 13-oxidocoralyne (7) in nearly quantitative yield when an aerated solution of (5) was heated in the dark.Irradiation of a solution of (3) containing Rose Bengal with visible light afforded 8,13a-epidioxy-9,10-dimethoxy-2,3-(methylenedioxy)- 13-oxo-5,6,13,13a-tetrahydro-8H-dibenzoquinolizine (11) in 90percent yield.Under the same conditions, however, (7) gave 2'-acetylpapaveraldine (14) in 88percent yield.On the other hand, when an alcoholic solution of (5) or (7) containing sodium alkoxide was irradiated with a mercury lamp (Vycol filter) under bubbling oxygen, 6,7-dimethoxyisoquinolone (16) and 3-alkoxy-5,6-dimethoxy-3-methylisobenzofuran-1(3H)-one (17) or (18) were obtained in moderate yields.A reaction mechanism which involves the initial formation of an epidioxy-intermediate was evidenced by the fact that the photolysis of (7) was carried out in the presence of borohydride anion to give (16) and 5,6-dimethoxy-3-methylisobenzofuran-1(3H)-one (19).Irradiation of (11) in the same fashion gave berberal (20) and 2-(2-formyl-3,4-dimethoxybenzoyl)-3,4-dihydro-6,7-(methylenedioxy)isoquinolin-1(2H)-one (21) in 72percent and 4percent yields, respectively.Possible mechanisms are also presented.Reduction of (3) with sodium borohydride gave (+/-)-ophiocarpine (9) and (+/-)-13-epiophiocarpine (10), with the ratio (9):(10) varying depending upon the nature of the alcohol used as solvent.An interpretation which rationalizes these observations is suggested.
