Uncommon intramolecular palladium-catalyzed cyclization of indole derivatives

A novel synthetic strategy based on the intramolecular palladium-catalyzed oxidative cyclization reaction, allows the formation of C-C bond and the synthesis of β-carbolinones. The reaction has been performed in the presence of catalytic amount of PdCl₂(CH₃CN)₂ and benzoquinone as a reoxidant.     

Synthesis of N-substituted indole derivatives via PIFA-mediated intramolecular cyclization

[Structure: see text] A variety of N-arylated and N-alkylated indole derivatives were synthesized by way of a phenyliodine bis(trifluoroacetate) (PIFA)-mediated intramolecular cyclization. This novel method allows for the construction of an indole skeleton by joining the N-atom on the side chain to the benzene ring at the last synthetic step. Other novel pyrrole-fused aromatic compounds can also be achieved by this method.     

Synthesis of derivatives of indole and quinoline by the intramolecular catalytic cyclization of allylanilines

An effective method for the isolation of 3-methyl-2-ethylindole and 2,4-dimethyl-quinoline by the intramolecular cyclization of N-(1-methyl-2-butenyl)- and 2-(1-methyl-2-butenyl)anilines under the action of the catalyst PdCl₂ (DMSO)_n was developed. The influence of the nature of the solvent, the temperature, and the concentration of the catalyst on the yield and the ratio of the reaction products was investigated.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 325–327, March, 1986.     

Enantioselective synthesis of P-stereogenic benzophospholanes via palladium-catalyzed intramolecular cyclization

Enantioselective or diastereoselective intramolecular cyclization of functionalized secondary phosphines or their borane adducts catalyzed by chiral Pd(diphosphine) complexes gave P-stereogenic benzophospholanes in up to 70% ee. These results provide a new method for the synthesis of chiral phospholanes, which are valuable ligands in asymmetric catalysis. [reaction: see text]     

Copper-catalyzed domino intramolecular cyclization: a facile and efficient approach to polycyclic indole derivatives

A mild and efficient Cu(2)O-catalyzed domino intramolecular C-N coupling/C-Y (Y = O, S, N) bond formation was successfully achieved. Thus oxazino[3,2-a]indole, thiazino[3,2-a]indole and indolo[2,1-b]quinazoline derivatives were facilely assembled from readily accessible gem-dibromovinyl systems. The protocol is general and practical, affording a variety of the indole-incorporated products in good to excellent yields even under air atmosphere.     

A general and efficient palladium-catalyzed intramolecular cyclization reaction of beta-brominated porphyrins

A general and efficient synthesis of fused five-membered porphyrins from the readily available beta-brominated porphyrins via palladium-catalyzed intramolecular cyclization has been developed, which can be applied for various metal complexes of beta-brominated porphyrins or free base ones and generally results in good yields of the fused five-membered porphyrins.     

Synthesis and intramolecular cyclization of bisthiadiazinylmethane derivatives

Bisthiadiazinylmethane derivatives obtained from 1,2,6-thiadiazine 1,1-dioxides and formaldehyde, undergo unusual intramolecular cyclizations to thiadiazino [4,3-g] [2,1,3] benzothiadiazine tetraoxides. The structures of the newly synthesized compounds are discussed on the basis of ¹H and ¹³C-NMR data and X-ray analysis.     

Regioselectivity in the palladium-catalyzed addition of carbon nucleophiles to carbocyclic derivatives.

The regioselectivity of Pd-catalyzed malonate additions and arylations to cycloalkenyl esters can be predicted by completing a stereochemical analysis of the Pd-pi-allyl complex. The Pd-catalyzed malonate additions which have the greatest degree of regioselectivity are in which substituents have a steric influence in blocking the incoming nucleophile. Cyclopentenyl substrates displayed lower regioselectivity than the cyclohexyl counterparts presumably due to increased planarity of the system. Arylations using tin and hypervalent silicon reagents were compared.     

A new entry to polycyclic indole skeletons via palladium-catalyzed intramolecular heteroannulation

[reaction: see text] A one-step method was developed for elaboration of a variety of polycyclic indole skeletons via a novel palladium-catalyzed intramolecular indolization of 2-chloroanilines bearing tethered acetylenes. This novel intramolecular indolization method unveils an unusual syn amidopalladation pathway of a tethered alkyne.     

Synthesis of dipyrrolo-diazepine derivatives via intramolecular alkyne cyclization

A regioselective approach was developed for the synthesis of dipyrrolo-diazepine derivatives. The synthetic route to dipyrrolo-diazepines first involves the synthesis of dipyrromethanes, followed by reaction of propargyl bromide in the presence of NaH to attach one alkyne functionality to the pyrrole nitrogen atom. Intramolecular heterocyclization with NaH in DMF between the alkyne functionality and pyrrole nitrogen atom gave the desired structures in good yields.     

Mechanism of palladium-catalyzed diene cyclization/hydrosilylation: direct observation of intramolecular carbometalation

The results of kinetic, deuterium-labeling, and low-temperature NMR studies have established a mechanism for the palladium-catalyzed cyclization/hydrosilylation of dimethyl diallylmalonate (1) with triethylsilane involving rapid, irreversible conversion of the palladium silyl complex [(phen)Pd(SiEt(3))(NCAr)](+) [BAr(4)](-) [Ar = 3,5-C(6)H(3)(CF(3))(2)] (4b) and 1 to the palladium 5-hexenyl chelate complex [(phen)Pd[eta(1),eta(2)-CH(CH(2)SiEt(3))CH(2)C(CO(2)Me)(2)CH(2)CH=CH(2)]](+) [BAr(4)](-) (5), followed by intramolecular carbometalation of 5 to form the palladium cyclopentylmethyl complex trans-[(phen)Pd[CH2CHCH2C(CO2Me)2CH2CHCH2SiEt3](NCAr)]+ [BAr4]- (6), and associative silylation of 6 to release 3 and regenerate 4b.     

Microwave-mediated intramolecular Diels-Alder cyclization of biodihydroxylated benzoic acid derivatives

The synthetic utility of biodihydroxylated benzoic acid derivatives for the construction of bridge bicyclo scaffolds was investigated. Biodihydroxylation of benzoic acid using Ralstonia eutropha B9 gave (1S,2R)-1,2-dihydroxycyclohexa-3,5-diene-1-carboxylic acid (DCD) in high optical purity (>95% ee). Protection of the intermediate and subsequent functional group transformation gave the required cyclization precursors in moderate to excellent overall yields. Subsequent intramolecular Diels-Alder cyclization of biodihydroxylated benzoic acid derivatives was carried out using either thermal or microwave conditions. Enantiomerically pure products with five chiral centers were obtained in 4-6 steps from achiral starting material.     

New palladium-catalyzed aerobic oxidative cleavage and cyclization of N-aryl peptide derivatives

Oxidative cleavage and cyclization cascades of N-aryl peptides have been achieved under palladium catalysis with air as the sole stoichiometric oxidant.     

One-pot,three-component synthesis of highly functionalized pyrimidone derivatives and access to indole fused pyrimidones via palladium-catalyzed intramolecular Heck reaction

A simple and facile approach to highly functionalized pyrimidone derivatives and indole fused pyrimidones has been developed. The synthesis of substituted pyrimidone derivatives in moderate to good yields involves [4+2] cycloaddition of 1,4-dipoles generated from α,β-unsarurated imines and dimethyl acetylenedicarboxylate (DMAD) with isocyanates as dipolarophiles. Furthermore, the pyrimidones resulted from 2-bromophenyl isocyanate could be transformed into various indole fused pyrimidones via intramolecular palladium-catalyzed Heck reaction under different conditions.     

New Heck coupling strategies for the arylation of secondary and tertiary amides via palladium-catalyzed intramolecular cyclization

A new synthetic protocol has been developed for the arylation of secondary and N-alkylated amide Heck precursors by the implementation of the palladium-catalyzed intramolecular Heck reaction strategies.     

Cu(I)-catalyzed cascade intramolecular cyclization of 2-propynol phenyl azides and diarylphosphine oxides for the synthesis of bisphosphorylated indole derivatives

The [Cu(OTf)]₂·C₆H₆ catalyzed cascade intermolecular addition–intramolecular cyclization reaction of easily prepared 2-propynol phenyl azides and diarylphosphine oxides was developed. This novel reaction leads to simultaneous formation of one C–N and two C–P bonds in a single step to give bisphosphorylated indole derivatives under mild conditions in moderate to good yields.     

Extending Pummerer reaction chemistry. Application to the oxidative cyclization of indole derivatives

Treatment of 2-(phenylsulfinyl)indoles bearing a pendant nucleophile at C(3) with Tf(2)O/lutidine triggers a Pummerer-like cyclization to furnish 3,3-spirocyclic-2-(phenylthio)indolenine products, which can, in turn, be hydrolyzed to 3,3-spirocyclic oxindoles. [reaction: see text]     

A facile synthesis of indolo[3,2,1-jk]carbazoles via palladium-catalyzed intramolecular cyclization

A new efficient synthesis of indolo[3,2,1-jk]carbazoles by the palladium-catalyzed cyclization of N-(2-bromoaryl)carbazoles is described. The reaction involves intramolecular C-C bond formation, coupled with the cleavage of a C-X bond and a C-H bond on carbazole ring. Substitutions on N-aryl core with either electron-donating or electron-withdrawing groups are introduced, and different reaction factors for cyclization are evaluated.