Synthesis of heterocycles via electrophilic cyclization of alkynes containing heteroatom

Cu-Catalyzed Transannulation Reaction of Pyridotriazoles with Terminal Alkynes under Aerobic Conditions: Efficient Synthesis of Indolizines

The Cu(I)-catalyzed denitrogenative transannulation reaction of pyridotriazoles with terminal alkynes en route to indolizines was developed. Compared to the previously reported Rh-catalyzed transannulation reaction, this Cu-catalyzed method features aerobic conditions and much broader scope of pyridotriazoles and alkynes.

Rhodium(iii)-catalyzed annulation of arenes with alkynes assisted by an internal oxidizing N–O bond

Rh(iii)-catalyzed C–H activation of 3-aryl-dihydroisoxazoles in the coupling with diarylacetylenes has been developed under redox-neutral conditions.

Recyclable (PhSe)2-catalyzed selective oxidation of isatin by H2O2: a practical and waste-free access to isatoic anhydride under mild and neutral conditions

A practical and waste-free synthesis of isatoic anhydride was reported. The feature of this methodology is the simple isolation procedure by filtration, which facilitates the direct recovery and reuse of both organoselenium catalysts and solvents.

Silver-catalyzed direct spirocyclization of alkynes with thiophenols: a simple and facile approach to 3-thioazaspiro[4,5]trienones

A convenient and efficient silver-catalyzed direct oxidative spirocyclization of alkynes with thiophenols leading to 3-thioazaspiro[4,5]trienones has been developed under air.

Regioselective and diastereoselective iodocyclization reaction of alkene-thioureas: an efficient approach to bicyclic β-lactams

Bicyclic β-lactams, i.e. 3-thia-1-dethiacephams were synthesized via a highly regioselective and diastereoselective iodocyclization reaction of alkene-thioureas with molecular iodine.

Ni(ii)-catalyzed dehydrative alkynylation of unactivated (hetero)aryl C–H bonds using oxygen: a user-friendly approach

Ni(ii)-catalyzed dehydrative alkynylation of unactivated C(sp²)–H bonds with terminal alkynes under atmospheric pressure of oxygen is described.

O-Transfer-facilitated cyclizations of propargylamides with TMSN3: selective synthesis of tetrazoles and dihydroimidazoles

Herein, we disclose the O-transfer-facilitated cyclizations of propargylamides with TMSN₃ to selectively afford functionalized tetrazoles and diiodomethylated dihydroimidazoles.

NIS-mediated intramolecular oxidative α-functionalization of tertiary amines: transition metal-free synthesis of 1,2-dihydro-(4H)-3,1-benzoxazin-4-one derivatives

A novel method for direct α-functionalization of tertiary amines via NIS-mediated oxidative C–O bond formation, where NIS serves as both an oxidant and an iodination reagent, has been developed.

Access to polysubstituted indoles or benzothiophenes via palladium-catalyzed cross-coupling of furfural tosylhydrazones with 2-iodoanilines or 2-iodothiophenols

Palladium-catalyzed cross-coupling of furfural tosylhydrazones with 2-iodoanilines or 2-iodothiophenols produces polysubstituted indoles or benzothiophenes, respectively.

Fast and highly chemoselective alkynylation of thiols with hypervalent iodine reagents enabled through a low energy barrier concerted mechanism

Among all functional groups, alkynes occupy a privileged position in synthetic and medicinal chemistry, chemical biology, and materials science. Thioalkynes, in particular, are highly useful, as they combine the enhanced reactivity of the triple bond with a sulfur atom frequently encountered in bioactive compounds and materials. Nevertheless, general methods to access these compounds are lacking. In this article, we describe the mechanism and full scope of the alkynylation of thiols using ethynyl benziodoxolone (EBX) hypervalent iodine reagents. Computations led to the discovery of a new, three-atom concerted transition state with a very low energy barrier, which rationalizes the high reaction rate. On the basis of this result, the scope of the reaction was extended to the synthesis of aryl- and alkyl-substituted alkynes containing a broad range of functional groups. New sulfur nucleophiles such as thioglycosides, thioacids, and sodium hydrogen sulfide were also alkynylated successfully to lead to the most general and practical method yet reported for the synthesis of thioalkynes.

A new strategy to construct a C=C-CF3 subunit via CuBr-catalyzed domino reaction of homopropargyl amines: an efficient synthesis of trifluoromethyl containing building blocks 4-trifluoromethyl-2,3-dihydro-pyrroliums

A new strategy for the construction of a C=C-CF3 subunit has been developed via CuBr-catalyzed domino cyclization-trifluoromethylation of homopropargyl amines with Umemoto's reagent. 4-Trifluoromethyl-2,3-dihydro-pyrroliums were produced in high yields. The usefulness of these products has been demonstrated by the transformation of them into various other trifluoromethylated molecules.

Recent advances in the synthesis of thiophene derivatives by cyclization of functionalized alkynes

This review is intended to highlight some recent and particularly interesting examples of the synthesis of thiophene derivatives by heterocyclization of readily available S-containing alkyne substrates.

Access to novel imidazo[1,5-a]pyrazine scaffolds by the combined use of a three-component reaction and a base-assisted intramolecular cyclization

A novel and practical two-step approach to an intriguing class of imidazo[1,5-a]pyrazines with exocyclic C=X (X = CH2, O) bonds is described. The process utilizes a sequential three-component reaction of propargyl amine or aminoester, 1,2-diaza-1,3-dienes and isothiocyanates to furnish functionalized 2-thiohydantoins which are transformed into thiohydantoin-fused tetrahydropyrazines by subsequent regioselective base-promoted cyclization.

Stereoselective bromocyclization of allylated aldoxime ethers

The intramolecular bromoamination of allylated aldoxime ethers leads first to isoxazolidinium salts which then undergo a skeletal rearrangement to form bromo-5,6-dihydro-4H-1,3-oxazines. Aliphatic aldoxime ethers with α-protons undergo multiple brominations before rearrangement.

Metal-free oxidative ipso-carboacylation of alkynes: synthesis of 3-acylspiro[4,5]trienones from N-arylpropiolamides and aldehydes

A general and metal-free radical route to synthesis of 3-acylspiro[4,5]trienones is established that utilizes TBHP (tert-butyl hydrogenperoxide) as an oxidation and a reaction partner to trigger the oxidative ipso-carboacylation of N-arylpropiolamides with aldehydes. This method offers a new difunctionalization of alkynes through oxidative cross coupling of the aldehyde C(sp(2))-H bond with an ipso-aromatic carbon.