Benzo phenanthridine synthesis

X-ray crystal structure, 6, 516 Benzophenanthridines synthesis from anils, 2, 416 Benzophenanthridines, tetrahydro-synthesis, 2, 469 Benzo[c]phenanthridines synthesis, 2, 414 from aryl isocyanides, 2, 411 from benzynes, 2, 432 Benzo[i]phenanthridines synthesis, 2, 414 Benzophenanthridinones... 

Reaction of Ar-Benzenesulfonyl-3-[bis(methyIthio)methyIenel-2r3-dihydro-l/F-quinoline-4-one 6.36 with Allyl and Benzyl Anions A New Regiospecific Synthesis of Phenanthridines and Benzo[/]phenanthridines... 

A more recent synthesis via the 2-aryl-l-tetralone intermediate developed by Janin and Bisagni (93T10305) provides a route to the benzo[c]phe-nanthrid-6(5//)-ones and 6-chlorobenzo[c]phenanthridines. Synthesis of... 

Synthesis of quaternary benzo[c]phenanthridine alkaloids and their analogs 97AHC(67)345. 

The protoberberine alkaloids (5-75) play important roles as precursors in the biosynthesis of a variety of related isoquinoline alkaloids such as protopine, phthalideisoquinoline, spirobenzylisoquinoline, rhoeadine, inde-nobenzazepine, secoberbine, and benzo[c]phenanthridine alkaloids. Chemical transformations of protoberberines to these alkaloids are particularly interesting and exciting from the biogenetic viewpoint and further from ready availability of starting protoberberines in nature or synthesis. 

A biomimetic synthesis of benzo[c]phenanthridine alkaloids from a protoberberine via the equivalent of a hypothetical aldehyde enamine intermediate has been developed (130,131). The enamide 230 derived from berberine (15) was subjected to hydroboration-oxidation to give alcohol 231, oxidation of which with pyridinium chlorochromate afforded directly oxyche-lerythrine (232) instead of the expected aldehyde enamide 233. However, the formation of oxychelerythrine can be rationalized in terms of the intermediacy of 233 as shown in Scheme 41. An alternative and more efficient... 

The above biomimetic method was successfully applied to synthesis of 2,3,8,9-tetraoxygenated fully aromatized benzo[c]phenanthridine alkaloids such as nitidine (243) (134,135), fagaronine (244) (134,135), and oxyterihanine (242) (136) (Scheme 42). The former two alkaloids attract many synthetic... 

The reaction of 6.36 with allyl and benzyl anions was examined with a view to develop an efficient method for the synthesis of phenanthridines and their benzo[/]-derivatives. The dithioacetal 6.36 when reacted with allyl anions yielded the corresponding... 

R. D., Synthesis of Quaternary Benzo[c]phenanthridine Alkaloids and Their Analogues, 67, 345. 

The intramolecular ortho-arylation of aryl amide ions with aryl iodides has been recently applied to the synthesis of phenanthridines 25 in excellent yields (Scheme 10.49) [66], By applying the same procedure, N-(2-iodobenzyl) naphthalene-amine and N-(2-chlorobenzyl) naphthalen-1-amine yield benzo[a]- andbenzo[c] phenanthridines in 98% and 84% yields, respectively [66]. 

During the synthesis of alkaloids through berberine and benzo[c]phenanthridine rings, a key tricyclic intermediate may be made by reaction of orc/zo-iodobenzamides with the enolate anion from 2-acetylhomoveratric esters (equation 84)570. Cyclization occurs spontaneously under the reaction conditions. 

The phenanthridine skeleton is synthesized by photocyclization of the enamides prepared from cyclohexanonimines and benzoyl chlorides (17,18). The benzo[c]phenanthridine skeletons are formed from the enamides prepared from 2-tetralonimines and benzoyl chlorides (19,20). More conveniently, the skeletons of protoberberine alkaloids are readily synthesized from the enamides prepared by simple acylation of 1 -methyl-3,4-dihy-droisoquinolines with benzoyl chlorides (21-24). This berbine synthesis is one of the most typical examples of the application of enamide photocyclization to alkaloid synthesis and can be further extended to the facile synthesis of the skeletons of the yohimbine group of indole alkaloids (25,26). 

Chelidonine, a representative benzo[c]phenanthridine alkaloid (1,2), was synthesized as the first application of this reaction in natural product synthesis (145). Initial thermal opening of the four-membered ring in 299 led to the formation of a transient -o-quinodimethane (301), which has a dienamide structure in the diene part and is then trapped by the suitably positioned multiple bond in the same molecule. They applied this intramolecular reaction to the acetylenic cyclobutene 300 for the synthesis of ( )-chelidonine (Scheme 110). 

Subsequently, Abramovitch et al. employed the Pschorr cyclisation of 100 in a synthesis of benzo[c]phenanthridine 102 <63CJC2265>. The key step involved addition of an aryl radical to C3 of an isoquinoline and proceeded in good yield (Scheme 33). Notably, no products derived from cyclisation to the pendent arene were observed [see also Scheme 56]. 

Cyclization to the benzo[c]phenanthridine (127) competes with rearrangement to the ring-expanded product (128) on irradiation of the amine oxide (129). A practical synthesis of the chlorin macrocycle (130) has been developed by irradiation of the seco-compound (131) in tetrahydrofuran containing TFA and Hiinig s base this is thought to take place by photocyc-lization of the ISrr-tautomer (132), followed by elimination of methanol. Analogous approaches have been employed in the syntheses of ( )-bonellin dimethyl ester and 20-methyl- and 20-cyano-isobacteriochlorins. " ... 

Dimethyl azodicarboxylate (164) has been reported to undergo a [ 4 + 2] photocycloaddition to the diene (165) to give the 2,3-diazabicyclo[2.2.2]octene (166). An analogous solid-state addition has been described in the ox-azolone (167) to give the photodimer (IbS), and oxidation of the photoadduct derived from 1-oxoanhydromethylberberine and nitrosobenzene has been used in a synthesis of ring C-substituted benzo[c]phenanthridines. ... 

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