A convenient synthesis of acyclic conjugated enediynes

Highly Selective Synthesis of cis-Enediynes on a Ag(111) Surface

Cis-enediyne-type compounds have received much attention as potent antitumor antibiotics. The conventional synthesis of cis-enediynes in solution typically involves multiple steps and various side reactions. For the first time, selective one-step synthesis of cis-enediyne from a single reactant is reported on a Ag(111) surface with a yield up to 90 %. High selectivity for the formation of cis-enediyne originates from the steric effect posed by weak intermolecular interactions, which protect the cis-enediyne from further reaction. A series of comparative experiments and DFT-based transition-state calculations support the findings. The described synthetic approach for directing reaction pathways on-surface may illuminate potential syntheses of other unstable organic compounds.

Alkynylzirconation of alkynes and application to one-pot bisalkynylation of alkynes

Stereocontrolled alkynylzirconation of unactivated alkynes was achieved by the reaction of an alkyne with Cp2ZrEt2 and alkynyl halide in this order. After hydrolysis of the alkynylzirconation product, trisubstituted enyne derivatives were obtained in good yields. Functionalized enynes were also prepared by the reaction of the alkynylzirconation products with a variety of electrophiles. Subsequent addition of the second alkynyl halide to the alkynylzirconation products provided an in situ protocol for bisalkynylation of alkynes into (Z)-enediynes in good yields.

Synthesis of Bicyclic Enediynes from Bis[phenyl[(trifluoromethanesulfonyl)oxy]iodo]acetylene: A Tandem Diels-Alder/Palladium(II)- and Copper(I)-Cocatalyzed Cross-Coupling Approach

The reaction of bicycloalkenylbis(phenyliodonium) triflates 1a or b (available via the Diels-Alder reaction of bis[phenyl[(trifluoromethanesulfonyl)oxy]iodo]acetylene with cyclopentadiene or furan, respectively) with alkynylstannanes 2a-g at room temperature in DMF in the presence of catalytic amounts of trans-benzyl(chloro)bis(triphenylphosphine)palladium(II) and copper(I) iodide proceeds smoothly and with selectivity to afford good to excellent yields of bicyclic enediynes 3a-k.