19775-50-9Relevant academic research and scientific papers
Two-Carbon Ring Expansion of Cyclobutanols to Cyclohexenones Enabled by Indole Radical Cation Intermediate: Development and Application to a Total Synthesis of Uleine
Leclair, Alexandre,Wang, Qian,Zhu, Jieping
, p. 1209 - 1215 (2022/01/19)
A single-electron transfer (SET) oxidation of indole or benzo[b]thiophene to a radical cation reverses the intrinsic polarity of these π-excessive bicyclic heteroarenes. Here we report an oxidative two-carbon homologation of cyclobutanols to cyclohexenones under a visible-light photoredox catalysis. 1-(Indol-2-yl)cyclobutan-1-ols are converted to 2,3,4,9-tetrahydro-1H-carbazol-1-ones, important structural motifs found in alkaloids and pharmaceuticals, with a broad substrate scope. A mechanistic study suggests that the reaction is initiated by an SET from an indole to an excited acridinium salt to generate the radical cation, which is followed by two consecutive 1,2-alkyl migrations and a rearomatization. Benzo[b]thiophene-substituted cyclobutanols are similarly converted to 2,3-dihydrodibenzo[b,d]thiophen-4(1H)-ones. A total synthesis of (±)-uleine featuring this ring-expansion process is documented.
Enantioselective Total Synthesis of (+)-Nordasycarpidone, (+)-Dasycarpidone, and (+)-Uleine
Delayre, Bastien,Fung, Cédric,Wang, Qian,Zhu, Jieping
, (2021/07/12)
The structure of uleine type alkaloids is characterized by the presence of a bridged tetracyclic hexahydro-1H-1,5-methanoazocino[4,3-b]indole ring system 1. Various strategies have been developed to access this polycyclic structural motif. We report herein a one-step conversion of appropriately functionalized 1,3,4-trisubstituted cyclopent-1-ene to 1 by way of an integrated oxidation/reduction/cyclization (iORC) process. This domino sequence, initiated by oxidative cleavage of cyclopentene ring, generated subsequently a cyclohexenone, an indole and a 1,3-bridged piperidine ring through formation of one C?C and two C?N bonds. Compound 1 is subsequently converted to nordasycarpidone, dasycarpidone and uleine. The chirality of the molecule was introduced by enzymatic desymmetrization of commercially available meso cis-3,5-diacetoxy-1-cyclopentene.
Palladium-Catalyzed Ullmann Cross-Coupling/Tandem Reductive Cyclization Route to Key Members of the Uleine Alkaloid Family
Tang, Fei,Banwell, Martin G.,Willis, Anthony C.
, p. 2950 - 2957 (2016/04/26)
The trisubstituted cyclohexenone 12, generated through a palladium-catalyzed Ullmann cross-coupling reaction between o-iodonitrobenzene and a 4,5-trans-disubstituted 2-iodo-2-cyclohexen-1-one, engaged in a tandem reductive cyclization process upon exposur
Total synthesis of (-)-20-epiuleine via stereocontrolled one-pot asymmetric azaelectrocyclization followed by novel 1,4-addition reaction
Sakaguchi, Taku,Kobayashi, Shohei,Katsumura, Shigeo
experimental part, p. 257 - 264 (2011/02/24)
The first asymmetric total synthesis of an indole alkaloid, (-)-20-epiuleine, containing the 2,3,4-trisubstituted piperidine core, was achieved using a stereocontrolled one-pot asymmetric 6π-azaelectrocyclization followed by a stereoselective 1,4-addition
A Novel Polonovski Rearrangement of the Uleine Skeleton
Blechert, Siegfried
, p. 2073 - 2082 (2007/10/02)
Modified Polonovski reaction of the alkaloid uleine (3) and subsequent treatment with oxygen afford dasycarpidone (8) in 65percent yield.Polonovski reaction of 1,13-dihydrouleine yields uleine.After formation of the corresponding N-oxides, 3 and 10a have been allowed to react with acyl halides giving halogenated uleine derivatives.The traditional mechanism cannot account for the formation of the reaction products.
2-CYANO Δ3 PIPERIDEINES - IX GENERAL STRATEGIES FOR THE SYNTHESIS OF CORYNANTHE-STRYCHNOS TYPE INDOLE ALKALOIDS
Grierson, David S.,Harris, Martin,Husson, Henri-Philippe
, p. 3683 - 3694 (2007/10/02)
The syntheses of three Corynanthe-Strichnos type indole systems illustrate how 2-cyano Δ3 piperideines 1 can be used as synthons for a general approach to the construction of complex alkaloids.By condensation of amino-nitrile 23 with sodium dimethylmalonate and subsequent deprotection of indole N and ring closure in HCl/MeOH, the cis indoloquinolizidine 16a was prepared in 45 percent overall yield.The reaction of 2-cyano-Δ3-piperideine 30 with the anion of β-ketoester 29 gave the stable enamine 31 (Y: 91 percent).Cyclization of 31, or its corresponding aminonitrile equivalent 32 under acidic conditions (TsOH) gave 34.Decarboxylation of 34 gave N-methyldesethylidene dihydroervitsine 25.Treatment of dihydropyridinium salt 42, or 2-cyano-Δ3-piperideine 43 with Et2AlCN in benzene gave 4-cyano-Δ2-piperideine 44 (isolated as its 2,4-dicyano adduct 45 in 37 percent yield).Mannich condensation of 45 with indole gave the epimeric nitriles 46a and b (Y: 65 percent).These compounds were reacted separately with CH3Li giving ketones 49 and 51 (Y:90 percent).Reaction of both 49 and 51 with 10-camphorsulfonic acid gave 20-epiuleine 36.
A STEREOSELECTIVE SYNTHESIS OF dl-3-EPIULEINE
Natsume, Mitsutaka,Kitagawa, Yoshinori
, p. 839 - 840 (2007/10/02)
A stereoselective synthesis of an indole alkaloid, 3-epiuleine, in racemic form is described.The key step involved is the ethylation of readily accessible compound 5 with Et2CuLi
