Palladium-Catalyzed Annulation Research Articles

Palladium-catalyzed annulation reactions of methyl o-halobenzoates with azabicyclic alkenes: a general protocol for the construction of benzo[c]phenanthridine derivatives

The annulation reaction of methyl o-halobenzoates with azabicyclic alkenes proceeds efficiently to give the corresponding benzo[c]phenanthridine derivatives in good to excellent yields using a developed base-free methodology based on our preliminary studies. Thirty-seven application examples validate the compatibility of the present strategy with different groups, particularly with the electron-deficient ones, that are difficult to access using other traditional methods. In addition, annulation reactions with non-symmetric azabicyclic alkenes are achieved in high regioselectivity.

Palladium-Catalyzed Annulation of 2,2′-Diiodobiphenyls with Alkynes: Synthesis and Applications of Phenanthrenes

A range of phenanthrene derivatives were efficiently synthesized by the palladium-catalyzed annulation of 2,2'-diiodobiphenyls with alkynes. The scope, limitations and regioselectivity of the reaction were investigated. The described method was adopted to synthesize 9,10-dialkylphenanthrenes, sterically overcrowded 4,5-disubstituted phenanthrenes and phenanthrene-based alkaloids. Reactions of highly methoxy-substituted biphenyls with 2-(2-propynyl)pyrrolidine and 2-(2-propynyl)piperidine gave 2-(9-phenanthylmethyl)pyrrolidines and 2-(9-phenanthylmethyl)piperidines, respectively. The products were transformed to phenanthroindolizidine and phenanthroquinolizidine alkaloids by the Pictet-Spengler reaction.

Palladium-catalyzed annulation of arynes by o-halobenzamides: synthesis of phenanthridinones.

The palladium-catalyzed annulation of arynes by substituted o-halobenzamides produces N-substituted phenanthridinones in good yields. This methodology provides this important heterocyclic ring system in a single step by simultaneous C-C and C-N bond formation, under relatively mild reaction conditions, and tolerates a variety of functional groups.

Palladium-Catalyzed Annulation of Allenes with Indole-2-carboxylic Acid Derivatives: Synthesis of Indolo[2,3-c]pyrane-1-ones via Ar–I Reactivity or C–H Functionalization

Two methodologies, one involving Ar-I reactivity and the other through C-H functionalization, for the formation of indolo[2,3-c]pyrane-1-ones via the corresponding allenes, are presented. A highly efficient approach to indolo[2,3-c]pyrane-1-one derivatives through the Pd-catalyzed regioselective annulation of allenes with 3-iodo-1-alkylindole-2-carboxylic acids is described. This method is fairly general for a wide range of allenes affording the respective indolo[2,3-c]pyrane-1-ones in good to excellent yields. In addition, a Pd(II)-catalyzed oxidative coupling of indole-2-caboxylic acid derivatives with allenes via direct C-H functionalization to afford the corresponding indolo[2,3-c]pyrane-1-ones in moderate to good yields has been developed.

Synthesis of Cyclopentacarbazolones via Palladium-Catalyzed Annulation of Internal Alkynes

Synthesis of Cyclopentacarbazolones via Palladium-Catalyzed Annulation of Internal Alkynes

ChemInform Abstract: Synthesis of 1,6‐Dihydropyrrolo[2,3‐g]indazoles Using Larock Indole Annulation.

Abstract The synthesis of 1,6-dihydropyrrolo[2,3-g]indazole derivatives is described. The indolic ring system is constructed via a Larock palladium-catalyzed annulation using terminal and internal alkynes. Additionally, when using internal alkynes for this reaction, we found that a directing effect on regioselectivity was mediated by the ester group of alkyl 3-substituted propiolate derivatives.

Synthesis of anti-HIV lithospermic acid by two diverse strategies

An efficient and convergent route for the synthesis of the natural product (+)-lithospermic acid, which possesses anti-HIV activity, was accomplished. The (±)-trans-dihydrobenzo[b]furan core therein was prepared by two different strategies. The first strategy involved the use of a palladium-catalyzed annulation to generate an appropriately substituted benzo[b]furan ester followed by a stereoselective reduction of a carbon-carbon double bond with Mg-HgCl(2)-MeOH. The second strategy relied on an aldol condensation between a suitably substituted methyl arylacetate and 3,4-dimethoxybenzaldehyde, followed by cyclization. Finally, a total synthesis of (+)-lithospermic acid was completed via coupling of a trans-dihydrobenzo[b]furan cinnamic acid with an enantiomerically pure methyl lactate.

ChemInform Abstract: Synthesis of 3,4‐Disubstituted Cinnolines by the Pd‐Catalyzed Annulation of 2‐Iodophenyltriazenes with an Internal Alkyne.

A simple and efficient synthesis of cinnolines was achieved by a palladium-catalyzed annulation methodology. 3,4-Disubstituted cinnolines are prepared via palladium-catalyzed annulation of 2-iodophenyltriazenes with an internal alkyne in moderate to good yields. Several internal alkynes are applicable to this reaction and it is compatible with a number of functional groups.

Palladium-Catalyzed Annulation Reactions for Diastereoselective Cyclopentene Synthesis

Palladium-catalyzed annulation reactions of conjugate acceptors and allenyl boronic ester provide substituted cyclopentenes in high yields and, where applicable, diastereoselectivities. This method provides rapid assembly of building blocks for natural product synthesis, including polycyclic lactone and lactam products. Reactions are hypothesized to initiate by conjugate addition of a nucleophilic propargylpalladium complex.

Synthesis of 1,6-dihydropyrrolo[2,3- g]indazoles using Larock indole annulation

The synthesis of 1,6-dihydropyrrolo[2,3- g]indazole derivatives is described. The indolic ring system is constructed via a Larock palladium-catalyzed annulation using terminal and internal alkynes. Additionally, when using internal alkynes for this reaction, we found that a directing effect on regioselectivity was mediated by the ester group of alkyl 3-substituted propiolate derivatives.

Synthesis of 3,4-disubstituted cinnolines by the Pd-catalyzed annulation of 2-iodophenyltriazenes with an internal alkyne

A simple and efficient synthesis of cinnolines was achieved by a palladium-catalyzed annulation methodology. 3,4-Disubstituted cinnolines are prepared via palladium-catalyzed annulation of 2-iodophenyltriazenes with an internal alkyne in moderate to good yields. Several internal alkynes are applicable to this reaction and it is compatible with a number of functional groups.

Intramolecular palladium-catalysed enolate arylation of 2- and 3-iodoindole derivatives for the synthesis of β-carbolines, γ-carbolines, and pyrrolo[3,4-b]indoles

The palladium-catalysed intramolecular α-arylation of carbonyl compounds with amino-tethered 2- and 3-iodoindoles provides a useful methodology for the synthesis of indolo-b-fused nitrogen heterocycles. A variety of substituted tetrahydro β- and γ-carbolines, and pyrrolo[3,4-b]indoles, have been prepared by means of this palladium-catalysed annulation process.

Synthesis of 3-(aminomethylene)-2-oxoindolines by palladium-catalyzed annulation of 3-chloro-2-iodo-N-arylacrylamides with amides or amines

A new palladium-catalyzed C-H bond activation-annulation-amination tandem method was presented for selectively synthesizing 3-(aminomethylene)-2-oxoindolines. In the presence of Pd(dba)(2), xantphos (L8), AgOAc and Na(2)CO(3), a variety of 3-chloro-2-iodo-N-arylacrylamides underwent the reaction with amides or amines to afford the corresponding 3-(aminomethylene)-2-oxoindolines in moderate to good yields.

Organic photovoltaics incorporating fulleroisoquinolinones as n-type materials

Fulleroisoquinolinones have been synthesized by palladium-catalyzed annulation of N-alkyl benzamides with C(60). A device incorporating fulleroisoquinolinones and the conjugated polymer P3HT exhibited power conversion efficiency up to 2.3% under AM 1.5G irradiation.

Palladium-Catalyzed Annulation Route to 6H-Benzo[c]chromenes

Reported is the synthesis of 6H-benzo[c]chromenes 3 via the palladium-­catalyzed annulation of 2-(2-iodophenoxy)-1-­substituted ethanones 1 with arynes generated in situ from 2. Both EDGs and EWGs were uniformly ­tolerated on the 2-iodophenoxy starting material. A lower yield was observed for an aliphatic ketone (R² = Me, 30% yield) compared to the aromatic ketones. Application of substituted aryne precursors led to an equimolar mixture of regioisomers as expected. Two possible mechanisms are presented, although proof for the formation of the aryne (e.g. by trapping with furan) is lacking.

ChemInform Abstract: Synthesis of Isoindolo[2,1-a]indoles by the Palladium-Catalyzed Annulation of Internal Alkynes.

ChemInform Abstract: Synthesis of Isoindolo[2,1-a]indoles by the Palladium-Catalyzed Annulation of Internal Alkynes.

ChemInform Abstract: Synthesis of Isocoumarins and α-Pyrones via Palladium-Catalyzed Annulation of Internal Alkynes.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform Abstract: A Simple and Efficient Enantioselective Synthesis of 2-Alkylidene-3-alkyl-1,4-benzodioxanes by Palladium-Catalyzed Annulation of Benzene-1,2-diol and Propargylic Carbonates

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform Abstract: Formation of 4-Methylphenanthrenes in Palladium-Catalyzed Annulation of Diethyl 2,2′-Diiodo-4,4′-biphenyldicarboxylate with Internal Alkynes, Using Methyl Nitrobenzoates as the Methylating Agent.

The reaction of diethyl 2,2‘-diiodo-4,4‘-biphenyldicarboxylate (7) with diarylacetylenes in the presence of 3,5-(NO2)2C6H3CO2Me (MeDNB) or 4-(NO2)C6H4CO2Me (MePNB), Pd(OAc)2 (10 mol %), K2CO3, and Bu4NBr, in DMF at 100 °C, gives 4-methyl-9,10-diaryl-2,7-phenanthrenedicarboxylic acid diethyl esters in good yields. The methyl group at position 4 originates from the electron-deficient methyl nitrobenzoates. High regioselectivity for the annulation of 7 with nonsymmetrical diarylalkynes was observed with the selectivity controlled mainly by electronic factors rather than by steric factors. A competitive kinetic isotope study was carried out using a 1:1 mixture of MePNB and MePNB-d3 in the annulation reaction of 7 which gave 4-methyl- and 4-(methyl-d3)phenanthrene in a 67:33 ratio, leading to an apparent value of kH/kD = 1.26. Possible mechanisms for the methyl transferring process are discussed.

ChemInform Abstract: Palladium-Catalyzed Annulation Reaction of o-Bromobenzaldehydes with Carbonyl Compounds to Produce Naphthol and/or Naphthalene Derivatives.

ChemInform Abstract: Palladium-Catalyzed Annulation Reaction of o-Bromobenzaldehydes with Carbonyl Compounds to Produce Naphthol and/or Naphthalene Derivatives.