Cobalt‐ and Nickel‐Catalyzed Regio‐ and Stereoselective Reductive Coupling of Alkynes, Allenes, and Alkenes with Alkenes

Abstract

Transition-metal-catalyzed coupling of two different C-C pi components through a metallacycle intermediate is a highly atom economical method to construct C-C bonds in organic synthesis. The metal-catalyzed coupling of an alkene and alkyne generally gives an Alder-ene or reductive coupling product. In this article, we focus on the cobalt- and nickel-catalyzed reductive coupling of alkynes, allenes, and alkenes with alkenes. These reductive coupling reactions provide convenient methods for the synthesis of various alkenes, dienes, functionalized alkanes, lactones, lactams, and cyclic alcohols in a highly regio- and stereoselective manner. A chemselective formation of metallacyclopentene intermediate from the two different C-C pi components and a low-valence metal species plays a key role for the high regio- and stereoselectivity of the catalytic reaction.

Unpredictable cycloisomerization of 1,11-dien-6-ynes by a common cobalt catalyst

“…In order to explain the formation of products 2 – 5 we proposed a possible mechanism (Scheme 3) in accordance with the generally accepted concepts [15,18]. The crucial step of this mechanism is the formation of metallacycle 6 from unsaturated cobalt(I) species [Co(PR 3 ) 2 Br] and the double and the triple bond of dienyne 1 (see Supporting Information File 1 for the calculated structure of 6 ).…”

“…Over the last decade the application of the cobalt catalytic system CoBr 2 /phosphine ligand/Zn/ZnI 2 for the carbon–carbon bond formation has become a subject of a growing interest (for reviews see [15–21]). This catalytic system has many advantages, including the availability of the cobalt salts and high tolerance to organic functional groups (for some recent examples see [22–27]).…”

Cobalt‐Catalyzed Intermolecular [2+2] Cycloaddition between Alkynes and Allenes

“…[9] Ogoshi and co-workers reported cobalt-catalyzed [2+ +2] cycloadditions between 1,3enynes and vinylarenes to give 1-alkenylcyclobutenes. [11] Inspired by these precedents, [12][13][14] the present study began with exploration of the reaction between 4-octyne (1a)a nd cyclohexylallene (2a;T able 1; see Tables S1-S3 in the Supporting Information for more detail). [11] Inspired by these precedents, [12][13][14] the present study began with exploration of the reaction between 4-octyne (1a)a nd cyclohexylallene (2a;T able 1; see Tables S1-S3 in the Supporting Information for more detail).…”

“…[4] With alkyne as the other unsaturated reactant, the [2+ +2] cycloaddition leading to a3 -alkylidenecyclobutene skeleton has been extensively explored in intramolecular settings under either thermal [5] or transition metal catalyzed [6] conditions (Scheme 1a). [11] Inspired by these precedents, [12][13][14] the present study began with exploration of the reaction between 4-octyne (1a)a nd cyclohexylallene (2a;T able 1; see Tables S1-S3 in the Supporting Information for more detail). [7c,d] To our knowledge,s elective intermolecular [2+ +2] cycloaddition between electronically unbiased alkynes and allenes under transition-metal catalysis remains elusive,w hereas different types of allene/ alkyne cycloadditions and dimerizations have been reported using rhodium and nickel catalysts.…”

Regiodivergent Ligand‐Controlled Rhodium‐Catalyzed [(2+2)+2] Carbocyclization Reactions with Alkyl Substituted Methyl Propiolates

“…[15] The divergence occurs for the preferential migratory insertion of the metal-alkyl bond in b to provide metallabicycloheptadiene c (cycle A), versus the metal-vinyl bond in e to provide the metallabicycloheptadiene f (cycle B). As illustrated, the first step in each of these processes is the formation of the metallabicyclopentene b and e from the oxidative addition of the metal into the 1,6-enyne 1.…”