Pd(II)-Catalyzed Dehydrogenative Olefination of Terminal Arylalkynes with Allylic Ethers: General and Selective Access to Linear (Z)-1,3-Enynes

Abstract

This work demonstrates a green and efficient method to prepare 1,3-enynes via Pd(II)-catalyzed direct dehydrogenative olefination of terminal arylalkynes with unactived allylic ethers. Various terminal arylalkynes can participate in the reaction, stereoselectively affording the desired conjugated (Z)-1,3-enynes in moderate to good yields.

Cross‐Dehydrogenative Alkynylation: A Powerful Tool for the Synthesis of Internal Alkynes

“…Interestingly, this palladium‐catalyzed cross‐dehydrogenative coupling is applicable to the C−H alkynylation of allylic ethers (Scheme ) . Thus, by heating a mixture of 5 mol % of Pd(OAc) 2 , 6 mol % of bis(diphenyphosphino)propane (dppp), aromatic terminal alkynes and 10 equivalents of allylic ethers in HOAc/MeCN at 80 °C for 40 h under a dinitrogen atmosphere, the corresponding branched 1,3‐enynes were generated in 25 %‐88 % yields.…”

Nickel-Catalyzed 3,3-Dialkynylation of 2-Aryl Acrylamides: Direct Access to gem-Diethynylethenes via Double Vinylic C–H Bond Activation

“…Initially, a model reaction of 2-phenyl- N -(quinolin-8-yl)­acrylamide 1a with 1-bromotriisopropylsilylacetylene 2 as the alkynylating reagent under the catalysis of Ni­(cod) 2 with Na 2 CO 3 as the base at 120 °C for 26 h provided mostly the monoalkynylated product, ( Z )-2-phenyl-5-(triisopropylsilyl)­pent-2-en-4-ynamide ( 4a ) in 60% yield, and no ( E )-isomer was identified, indicating that the reaction goes via a C–H/C–X cross-coupling process rather than a Heck pathway . In addition, a small amount of dialkynylated product 3a was isolated.…”

Transition‐Metal‐Catalyzed Selective Alkynylation of C−H Bonds

“…Another report by Jiang and co‐workers employed bromoalkynes for the stereoselective synthesis of E ‐enynes from unactivated olefins using palladium catalysts [72] . Remarkably, Zhang, Zhong and co‐workers presented the synthesis of Z ‐enynes via the Pd(II) catalyzed alkynylation of allylic ethers [73] . However, these reactions usually require a large number of alkene substrates and seldom results in homocoupling of alkynes.…”