Bis(phosphine)cobalt-Catalyzed Highly Regio- and Stereoselective Hydrosilylation of 1,3-Diynes

Abstract

Seven bis­(phosphine) cobalt complexes and one tris­(phosphine) cobalt complex were tested for hydrosilylation of 1,3-diynes, among which dppp-CoCl2 (1 mol %) exhibited the best regio- and stereoselectivity, affording (E)-2-silyl-1,3-enynes through monohydrosilylation at the internal carbon of the 1,3-diyne unit via syn addition. Good functional tolerance was achieved, 32 substrates were tested, and the reactions could be readily amplified to a gram level. For most of the substrates, the transformation could be completed in 5 min at room temperature. To date, this is the most effective base-metal-catalyzed system for the selective hydrosilylation of 1,3-diynes.

Remote Site‐Selective Asymmetric Protoboration of Unactivated Alkenes Enabled by Bimetallic Relay Catalysis

“…( 4)]. [23] Moreover, given that a NHC-CoCl 2 catalyst can efficiently promote this chain-walking process [Eq. ( 5)], a stoichiometric reaction of Co(IMes) 2 Cl 2 , B 2 Pin 2 and NaO t Bu showed the formation of Co(IMes) 2 Cl [Eq.…”

Cobalt-Catalyzed (E)-Selective Hydrosilylation of 1,3-Enynes for the Synthesis of 1,3-Dienylsilanes

“…According to the previous studies, a proposed mechanism is shown in Scheme . Initially, the bisphosphine Co­(II)­Cl 2 complex reacts with NaHBEt 3 to generate the Co­(I)–H intermediate A .…”

“…More recently, Huang et al discovered a pincer Fe catalyst (2.0 mol %) for hydrosilylation of 4-alkyl-substituted, 1,4-disubstituted, and 1,1,4-trisubstituted 1,3-enynes, and after 12 h at 0 °C, a series of 4,3-adducts were generated (Scheme ). In consideration that Co catalysts are efficient for the selective hydrosilylation of alkynes and conjugated diynes, , we speculated that some of them might also be applied for hydrosilylation of 1,3-enynes. Co complexes based on a bisphosphine ligand can be good choices because many organic diphosphines are commercially available at low prices.…”

“…In consideration that Co catalysts are efficient for the selective hydrosilylation of alkynes and conjugated diynes, , we speculated that some of them might also be applied for hydrosilylation of 1,3-enynes. Co complexes based on a bisphosphine ligand can be good choices because many organic diphosphines are commercially available at low prices. Here, we present the Dppf-CoCl 2 -catalyzed hydrosilylation of 4-aryl-substituted 1,3-enynes and the Xantphos-CoCl 2 -catalyzed hydrosilylation of 4-alkyl-substituted 1,3-enynes, resulting in the isolation of a series of 3,4- and 4,3-adducts via syn -addition, respectively, under mild conditions.…”

Catalytic Hydrofunctionalization Reactions of 1,3-Diynes

“…In this context, Ge and colleagues reported in 2019 the regio-and stereoselective access to a broad range of silylfunctionalized 1,3-enynes by hydrosilylation of 1,3-diynes (syn addition), employing a catalyst generated from bench-stable Co(acac) 2 and 1,3-bis(diphenylphosphino)propane (dppp) (Scheme 29) [72]. Related hydrosilylation reactions, featuring the same regio-and stereocontrol, were subsequently described with other cobalt-based catalytic systems, such as complexes 51 [73] and 52 [74] (see Figure 8) or the CoCl 2 /dppp combination [75]. In these cases, the reducing agent NaHBEt 3 was systematically employed as a co-catalyst, allowing the reactions to proceed under milder conditions (r.t. or 30 • C) and shorter times (from 5 min to 1 h).…”