γ-Selective Allylation of (E)-Alkenylzinc Iodides Prepared by Reductive Coupling of Arylacetylenes with Alkyl Iodides

Abstract

The first examples of Cu-catalyzed γ-selective allylic alkenylation using organozinc reagents are reported. (E)-Alkenylzinc iodides were prepared by Fe-catalyzed reductive coupling of terminal arylalkynes with alkyl iodides. In the presence of a copper catalyst, these reagents reacted with allylic bromides derived from Morita–Baylis–Hillman alcohols to give 1,4-dienes in high yields. The reactions are highly γ-selective (generally γ/α > 49:1) and tolerate a wide range of functional groups such as ester, cyano, keto, and nitro.

Synergistic Copper/Palladium Catalysis for the Regio- and Stereoselective Synthesis of Borylated Skipped Dienes

“…Consequently, general methods that allow for the efficient and stereoselective preparation of skipped dienes are in high demand. Among the catalytic methodologies available for the synthesis of these important molecules, transition-metal-catalyzed allylic substitution using alkenylmetal reagents has become a powerful tool. − Great advances have been made in this field, and nowadays selective protocols based on palladium, copper, and iridium catalysis are available. However, these methodologies involve the preparation and use of stoichiometric amounts of basic alkenylmetal reagents.…”

Cobalt-catalyzed branched selective hydroallylation of terminal alkynes

“…Skipped dienes derivatives are important motifs in biologically active natural products and medicines [1][2][3] . Traditionally, there are several methods for the preparation of these useful compounds, such as allylation of alkenyl metallic reagents [4][5][6][7] , allyl metalation of alkynes [8][9][10][11][12] , and Alder ene reaction of alkynes 13,14 . However, these methods are mainly restricted to using stoichiometric amounts of metallic reagents or limited substrate scope.…”

Z-Selective Synthesis of Vinyl Boronates through Fe-Catalyzed Alkyl Radical Addition

“…Our approach is based on Fe-catalyzed stereoselective addition of an alkyl radical, generated from an alkyl halide under reductive conditions, to ethynylboronic acid pinacol ester ( 1 , Figure b). The approach is built upon our previous work, − which showed that an alkyl radical was generated through the reaction of an alkyl halide with an Fe­(I) species, produced by reduction of an Fe­(II) catalyst with Zn (Figure c,d). The alkyl radical could be trapped by a terminal aryl alkyne to form a vinyl radical stabilized by an aryl group.…”