Ni‐Catalyzed Cyclization of Enynes and Alkynylboronates: Atom‐Economical Synthesis of Boryl‐1,4‐dienes

Abstract

We report a novel atom‐economical Ni‐catalyzed cyclization reaction of enynes with alkynylboronates. The reaction employs a non‐expensive Ni salt, a phosphine‐based ligand and easy‐handling alkynylboronates as boron–carbon source. The reaction provides complex fused‐bicyclic compounds containing borylated 1,4‐cyclohexadienes in high yields in short reaction times, involving the formation of two C−C bonds in one step. A reasonable reaction mechanism is proposed based on mechanistic experimental results.

Nickel‐Catalyzed Arylative Cyclizations of Alkyne‐ and Allene‐Tethered Electrophiles using Arylboron Reagents

“…Overall, two new bonds are formed to give cyclic products, typically of general structure 4 or 7. It should be mentioned that mechanistically different transitionmetal-catalyzed arylative and alkylative cyclizations of alkyneand allene-tethered electrophiles also exist, which proceed via oxidative cyclization to give metallacyclic intermediates, [45][46][47][48][49][50][51][52][53][54][55][56][57][58][59] and these reactions are not covered in this review.…”

Regio- and stereocontrolled synthesis of borylated E-enynes, Z-enediynes and derivatives from alkenyl-1,2-bis-(boronates)

“…12 Boron-enyne is an important scaffold for the generation of enediyne systems. There are several reports in the literature on the synthesis of boryl-functionalized enynes catalyzed with metals such as Cu, Ni, Co and Pt [13][14][15][16][17][18][19][20] or with phosphine. 21 However, these reactions are neither regioselective nor stereoselective.…”