Cycloaddition Of Internal Alkynes Research Articles

Regioselective Synthesis of Diverse Thio-, Seleno-substituted 1,2,3-Triazoles

: Thio-, seleno-substituted triazoles are useful scaffolds employed in the fields of organic synthesis, medicinal chemistry, and material science. A number of synthetic approaches to efficient formation of thio- and seleno-triazoles have been disclosed, including the interception of copper(I) triazolides generated in-situ, cycloaddition of internal alkynes (thio-, halo-, and metalated alkynes) to azides, and the coupling of azides and nonalkyne substrates. This mini-review intends to summarize the synthetic methods toward thio-, seleno-1,2,3-triazoles and the relative reaction mechanisms.

A Chiral N,N′‐Dioxide–ZnII Complex Catalyzes the Enantioselective [2+2] Cycloaddition of Alkynones with Cyclic Enol Silyl Ethers

AbstractA highly efficient enantioselective [2+2] cycloaddition between alkynones and cyclic enol silyl ethers was developed by using a chiral N,N′‐dioxide‐zinc(II) complex as a catalyst. This method functions well for a variety of terminal alkynes as well as cyclic enol silyl ethers, with good to excellent enantioselectivity (up to 97 % ee). This is also the first successful example for the catalytic enantioselective [2+2] cycloaddition of internal alkynes with cyclic enol silyl ethers to give fully substituted cyclobutenes. Meanwhile, the desired cyclobutene product can easily be transformed into fused cyclobutane derivatives.

A Chiral N,N'-Dioxide-Zn(II) Complex Catalyzes the Enantioselective [2+2] Cycloaddition of Alkynones with Cyclic Enol Silyl Ethers.

A highly efficient enantioselective [2+2] cycloaddition between alkynones and cyclic enol silyl ethers was developed by using a chiral N,N'-dioxide-zinc(II) complex as a catalyst. This method functions well for a variety of terminal alkynes as well as cyclic enol silyl ethers, with good to excellent enantioselectivity (up to 97 % ee). This is also the first successful example for the catalytic enantioselective [2+2] cycloaddition of internal alkynes with cyclic enol silyl ethers to give fully substituted cyclobutenes. Meanwhile, the desired cyclobutene product can easily be transformed into fused cyclobutane derivatives.

Rhodium-Catalyzed [6 + 2] Cycloaddition of Internal Alkynes with Cycloheptatriene: Catalytic Study and DFT Calculations of the Reaction Mechanism

A rhodium-catalyzed [6 + 2] cycloaddition of internal alkynes with cycloheptatriene is described. A series of substituted alkynes were cycloadded to cycloheptatriene through a [6 + 2] addition to give a variety of substituted bicyclic compounds in excellent yields. The optimal catalytic system for these transformations was a [Rh(COD)Cl]2 (5.0 mol %) catalyst in combination with CuI (10 mol %) and PPh3 (10 mol %). The proposed mechanism for this system includes an initial oxidative coupling reaction between the coordinated cycloheptatriene and the internal alkyne, followed by a [1,3]-shift of the Rh metal center and a reductive elimination from the Rh(III)–allyl complex to give the final product. Calculations using a model Rh(I) catalyst were also carried out to further understand this mechanism.

Cobalt-Catalysed [6+2] Cycloaddition of Internal Alkynes and Terminal ­Alkenes with Cycloheptatriene

The cobalt-catalysed [6+2] cycloaddition of cycloheptatriene with internal alkynes as well as with terminal alkenes is described. The cycloaddition process is most efficiently catalysed by cobalt dibromide[bis(triisopropylphosphite)] complexes in dichloromethane as the solvent of choice. In the cobalt-catalysed reaction of cycloheptatriene with norbornene an unexpected tricyclic [2+2] cycloaddition product was isolated in excellent yields.