Cyclization Of Terminal Alkynes Research Articles

Cu‐catalyzed synthesis of 1‐naphthols with terminal alkynes and 2‐bromoaryl ketones

A Cu‐catalyzed straightforward synthesis of 1‐naphthols via an 6‐endo‐dig cyclization of terminal alkynes with 2‐bromoaryl ketones in water is reported. The Cu(I) catalytic system tolerates various electron‐withdrawing and electron‐donating functional groups on both substrates and exhibits unique 6‐endo‐dig selectivity to give 1‐naphthols in moderate to good yields.

Retracted: Direct synthesis of 1‐naphthylamines enabled by 6‐endo‐dig cyclization strategy using copper catalysis

Here, we describe a facile approach for the synthesis of substituted 1‐naphthylamines via three‐component 6‐endo‐dig cyclization of terminal alkynes with 2‐bromoaryl ketones, primary or secondary amines in water under Pd‐free conditions. The Cu(I) catalytic system avoids a fundamental problem related to these substrates, which competitively evolve through 5‐endo‐dig cyclization pathways under metal catalysis. This unique performance unlocks a rapid access to a diverse 1‐naphthylamines library that previously required longer synthetic routes. The synthetic potential of this method was further demonstrated by the gram‐scale synthesis, and the mechanism study showed that the reaction experienced sequential halide exchange, imine‐enamine tautomerization and 6‐endo‐dig cyclization.

Synthesis of 1-pyrroline derivatives via cyclization of terminal alkynes with 2-azaallyls.

An efficient transition-metal-free cyclization reaction to prepare 1-pyrroline derivatives bearing various functional groups is described. In this method, a simple combination of a base and a solvent allows the cyclization reaction of terminal alkynes and 2-azaallyls to be carried out efficiently under mild and metal-free conditions. This cyclization reaction will provide an efficient method for the synthesis of medicinally relevant polysubstituted and multifunctionalized pyrrolines.

Synthesis of 2,5-disubstituted selenophenes via a copper-catalyzed regioselective [2+2+1] cyclization of terminal alkynes and selenium.

Herein, a straightforward method for the synthesis of 2,5-disubstituted selenophenes via [2+2+1] cyclization of easily accessible terminal alkynes and elemental selenium has been developed. This reaction features high atom- and step-economy, excellent regioselectivity, good functional group tolerance and the use of stable and non-toxic selenium as a selenium source. A series of control experiments suggests that the reaction might undergo Glaser coupling reaction of two molecules of alkynes, followed by insertion of H2Se and subsequent cyclization. Moreover, the newly formed products can be further converted to diverse conjugated selenophene-based derivatives, demonstrating their potential applications in organic synthesis and materials science.

Photocatalytic Markovnikov-type addition and cyclization of terminal alkynes leading to 4-sulfonyl quinoline-2(1H)-ones.

A new and expedient photocatalytic protocol for the construction of quinolin-2(1H)-ones via Markovnikov-type sulfonylation/6-endo-trig cyclization/selective C(O)-CF3 bond cleavage starting from N-alkyl-N-(2-ethynylphenyl)-2,2,2-trifluoroacetamides and sulfinic acids has been developed. It is as an unprecedented protocol for the preparation of 4-sulfonylquinoline-2(1H)-ones with high efficiency, mild reaction conditions, acceptable yields and a wide range of substrates.

Visible light-induced deoxygenation/cyclization of salicylic acid derivatives and aryl acetylene for the synthesis of flavonoids

A visible-light-induced photocatalytic strategy for the synthesis of flavonoids has been developed through the deoxygenative/cyclization reaction of salicylic acid derivatives with aryl acetylene using diphenyl sulfide as an O-transfer reagent. Based on the controlled experiments, the mechanism of visible-light-induced free radical coupling cyclization was proposed. The protocol obtained 51 flavonoids in good yields and has been successfully applied to the synthesis of some natural flavones.

Atom Efficient Synthesis of Selectively Difluorinated Carbocycles through a Gold(I)-Catalyzed Cyclization.

The intramolecular carbocyclization of difluorinated enol acetals has been achieved for the first time using gold(I) catalysis. Difluorinated enol acetals bearing a pendant alkene group can be cyclized and reduced in one pot to form fluorinated diol motifs. Alternatively, the cyclization of terminal alkynes allows for the synthesis of fluorinated pyran scaffolds. Both cyclization processes can be performed under mild conditions allowing access to complex products rich in functionality. The cyclic systems are synthesized concisely (maximum four steps) from trifluoroethanol, an inexpensive fluorinated feedstock.

Synthesis and biological evaluation of benzimidazole-linked 1,2,3-triazole congeners as agents.

BackgroundBenzimidazoles and triazoles are useful structures for research and development of new pharmaceutical molecules and have received much attention in the last decade because of their highly potent medicinal activities.FindingsA simple and efficient synthesis of triazole was carried out by treatment of 2-(4-azidophenyl)-1H-benzo[d]imidazole (6) with different types of terminal alkynes in t-BuOH/H2O, sodium ascorbate, and Zn(OTf)2, screened for cytotoxicity assay and achieved good results. A series of new benzimidazole-linked 1,2,3-triazole (8a-i) congeners were synthesized through cyclization of terminal alkynes and azide. These synthesized congeners 8a-i were evaluated for their cytotoxicity against five human cancer cell lines. These benzimidazole-linked 1,2,3-triazole derivatives have shown promising activity with IC50 values ranging from 0.1 to 43 μM. Among them, the compounds (8a, 8b, 8c, and 8e) showed comparable cytotoxicity with adriamycin control drug.ConclusionsIn conclusion, we have developed a simple, convenient, and an efficient convergent approach for the synthesis of benzimidazole-linked 1,2,3-triazole congeners as agents.Graphical Synthesis of 1,2,3-triazole derivativesElectronic supplementary materialThe online version of this article (doi:10.1186/s13588-014-0014-x) contains supplementary material, which is available to authorized users.

ChemInform Abstract: Synthesis of (E)‐3‐Alkylidene‐1‐pyrrolines by the Rhodium‐Catalyzed Cyclization of Terminal Alkynes with Homopropargylic Amines.

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Synthesis of 2‐Substituted Indoles via Pd/C‐Catalyzed Reaction in Water.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Synthesis of 2-Substituted Indoles via Pd/C-Catalyzed Reaction in Water

A general and one-pot synthesis of 2-alkyl/aryl substituted indoles via a tandem Pd/C mediated coupling/5-endo-dig cyclization of terminal alkynes (including acetylenic carbinols) with o-iodoanilides in water is reported.The reaction is carried out using PPh 3 and Cul as co-catalysts and 2-aminoethanol as a base. The reaction appears to tolerate a variety of functional groups present in the alkynes and does not require the use of any organic co-solvent.

The first cobalt catalyzed [2 + 2 + 2] alkyne cyclotrimerization in aqueous medium at room temperature.

Chelate complex 1 (5 mol%) was found to catalyze the [2 + 2 + 2] cyclization of terminal alkynes in good yields in a 80/20 mixture of water and ethanol at room temperature without further activation.