Carbolines

The reaction of tert-butyl (3-indolyl)carbinol with potassium cyanide yielded a nitrile which was reduced to-tert-butyltryptamine. 1-Methyl-4-tert-butyl--carboline was prepared by cyclization of the acetyl derivative of this amine with subsequent dehydrogenation. An attempt to obtain this compound through 4-(3-indolyl)-5,5-dimethyl-2-hexanone was unsuccessful.See [1] for communication II.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 621–622, May, 1971.     

Carbolines

Two methods of synthesizing 4-aryl- and 4-hetaryl--carbolines are proposed. The reaction of indole with aryl- and hetarylnitroolefins leads to the formation of -aryl- and -hetaryl-nitroethylindoles, which are reduced to the corresponding tryptamines. The latter can be converted by the usual methods into 3,4-dihydro- and 1,2,3,4-tetrahydro--carbolines. The second route is illustrated by the reaction of indole with 3-phenylaziridine-2-carboxylic acid ester. The resulting -phenyltryptophan, on subsequent treatment with acetaldehyde in potassium dichromate solution, is smoothly converted into 4-phenylharman.For Communication V, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1523–1527, November, 1973.     

Carbolines

The synthesis of 1-methyl-4-(-dimethylaminopropyl)--carboline from 3-(1-methyl-2-pyrrolidyl)indole is described.See [1] for communication IV.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 337–339, March, 1973.     

Carbolines

6-Benzyloxy-3-hexen-2-one, which served as the starting compound for the synthesis of 1-methyl-4-(2-benzyloxyethyl)-3,4-dihydro--carboline by a previously described method, was obtained by the reaction of -benzyloxypropionaldehyde with diethylphosphonoacetone.See [1] for communication III.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1074–1075, August, 1971.     

Carbolines

Unsaturated nitriles, which were reduced in two steps to tryptamines, were obtained by reaction of 3-indolylacetonitrile with heterocyclic aldehydes. Substituted -carbolines were synthesized by cyclization of the acetyl derivatives of the tryptamines and subsequent photochemical dehydrogenation.See [1] for the preceding communication.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1382–1387, October 1974.     

Carbolines

Anhydronium bases of 2-chloro--carbolines and 3,4-dihydro--carbolines are formed fay Beckmann rearrangement of - (3-indolyl) ketone oximes. In a number of cases the formation of anhydronium bases becomes the predominant process.See [1] for communication VII.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 386–391, March, 1976.     

Carbolines. 14. Synthesis of 5-azaellipticine

3-Acetyl-4-methylaminopyridine was obtained by cyanation of 3-acetylpyridine ethyleneketal N-oxide and subsequent chemical transformations of the nitrile group. Condensation of this product with oxindole led to the synthesis of 5H-5,11-dimethylindolo [3,2-j]-1,4-naphthyridine — the aza analog of the alkaloid ellipticine.See [1] for communication 13.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1211–1214, September, 1982.     

Carbolines,Part VIII. An Original Synthesis of the Antibiotic Eudistomin T

An original and short synthesis of Eudistomin T is reported. The approach is based on a convergent methodology which involves such reactions as metalation, heteroring cross-coupling and cyclization.     

Carbolines. Part VII. Anisidines,convenient tools to synthesize hydroxy-β-carbolines

The paper describes a convenient synthesis of hydroxy-β-carbolines from commercial anisidines based on key steps such as metalation, cross-coupling and cyclization. The first total synthesis of a major cyto-toxic constituent of a marine bryozoan is also reported, the 8-hydroxy-1-vinyl-β-carboline.     

Alkenyl Isocyanide Conjugate Additions: A Rapid Route to γ‐Carbolines

Isocyanides are exceptional building blocks, the wide deployment of which in multicomponent and metal‐insertion reactions belies their limited availability. The first conjugate addition/alkylation to alkenyl isocyanides is described, which addresses this deficiency. An array of organolithiums, magnesiates, enolates, and metalated nitriles add conjugately to β‐ and β,β‐disubstituted arylsulfonyl alkenyl isocyanides to rapidly assemble diverse isocyanide scaffolds. The intermediate metalated isocyanides are efficiently trapped with electrophiles to generate substituted isocyanides incorporating contiguous tri‐ and tetra‐substituted centers. The substituted isocyanides are ideally functionalized for elaboration into synthetic targets as illustrated by the three‐step synthesis of γ‐carboline N ‐methyl ingenine B.     

Divergent Synthesis of Hydro‐γ‐Carbolines and Multisubstituted Indoles through Grob Fragmentation/Mannich Cyclization

A distinct strategy for the divergent synthesis of hydro‐γ‐carbolines and multisubstituted indoles is reported. The stereochemical outcomes and a control experiment indicate that the reactions likely proceed through Grob fragmentation/Mannich cyclization rather than a concerted aza‐pinacol rearrangement.     

Construction of Chiral Tetrahydro‐β‐Carbolines: Asymmetric Pictet–Spengler Reaction of Indolyl Dihydropyridines

A highly efficient synthesis of the enantioenriched tetrahydro‐β‐carbolines was developed by using a chiral phosphoric acid catalyzed Pictet–Spengler reaction of indolyl dihydropyridines. The reaction proceeds under mild reaction conditions to afford the desired chiral tetrahydro‐β‐carbolines in good to excellent yields (up to 96 %) and high enantioselectivities (up to 99 % ee ). With this method, a formal synthesis of tangutorine and a total synthesis of deplancheine were achieved in a highly efficient manner.     

Zinc‐Catalyzed Alkyne Oxidation/CH Functionalization: Highly Site‐Selective Synthesis of Versatile Isoquinolones and β‐Carbolines

An efficient zinc(II)‐catalyzed alkyne oxidation/C? H functionalization sequence was developed, thus leading to highly site‐selective synthesis of a variety of isoquinolones and β‐carbolines. Importantly, in contrast to the well‐established gold‐catalyzed intermolecular alkyne oxidation, over‐oxidation can be completely suppressed in this system and the reaction most likely proceeds by a Friedel–Crafts‐type pathway. Mechanistic studies and theoretical calculations are described.     

Enantioselective Friedel–Crafts Alkylation of Indoles with Alkylidene Malonates Catalyzed by N,N′‐Dioxide–Scandium(III) Complexes: Asymmetric Synthesis of β‐Carbolines

An efficient catalytic asymmetric Friedel–Crafts alkylation of indoles with alkylidene malonates has been developed by using a chiral N,N′‐dioxide–Sc(OTf)₃ complex as the catalyst (see scheme). Some optically active intermediates containing the indole skeleton have been synthesized, such as indolepropionic acid, tryptamines, and β‐carbolines. The coordination between the scandium atom and the chiral N,N′‐dioxide compound has been revealed by X‐ray structure analysis.