Cobalt-Catalyzed Regio- and Stereoselective Hydrosilylation of 1,3-Diynes To Access Silyl-Functionalized 1,3-Enynes

Abstract

A regio- and stereoselective hydrosilylation of 1,3-diynes has been developed relying on catalysts generated from bench-stable Co­(acac)2 and dppp ligand. A variety of symmetrical and unsymmetrical 1,3-diynes undergo this transformation, yielding the corresponding silyl-functionalized 1,3-enynes in high yields with excellent regioselectivity. Gram-scale reactions and further transformations of the silyl-containing 1,3-enyne products highlight the synthetic utilities of this Co-catalyzed hydrosilylation of 1,3-diynes.

Hydroelementation of diynes

“…Therefore, considering the reaction methodology, conditions, and application of a specific type of catalyst (often tailored-made) is of prior importance, especially when such complex diyne molecules are used as reagents. 68,73,74,156,163 The simplicity of the hydrosilylation process, its high tolerance towards various functional groups present in the reagent structures, as well as the diversity of the selectivities, which can be tuned by the proper choice of the catalyst, has rendered this transformation the first choice for the synthesis of organosilicon compounds. The reactivity of the silyl group in coupling reactions or desilylation processes has allowed the application of the resulting compounds (e.g., 1,3-enyne or 1,3-diene fragments), in the synthesis of natural or biologically active compounds.…”

“…Depending on the type of the catalyst, reagents, their concentration, ratio, and process conditions, silylated 1,3-enynes, 1,3dienes, or allenes can be formed, frequently as a complex mixture of products (up to nine different compounds can potentially be formed). 62,73,74,156,164 Many papers describe the hydrosilylation of monoalkynes, 14,41,48,49,51 but the addition of the Si-H bond to 1,3-diynes is much more demanding and limited only to a few papers. The hydrosilylation of 1,3-diynes occurs mainly in the presence of noble metal complexes (Rh, Pt, Pd, Ru).…”

“…might be applied in various transformations leading to fine organic and organometallic compounds and materials. 67,68,[156][157][158][159][160][161][162] This broad applicability is a result of the ease of substitution of the silyl group with a broad range of functional groups, as well as the formation of different silylated products: 1,3-enynes, allenes, polymers, or cyclic compounds, depending on the type of diyne starting material (conjugated or separated with alkyl or aryl spacers). Moreover, silyl-substituted compounds are easy to handle, simple for isolation, stable in air, and active in many chemical transformations.…”

“…The reactivity of the silyl group in coupling reactions or desilylation processes has allowed the application of the resulting compounds (e.g., 1,3-enyne or 1,3-diene fragments), in the synthesis of natural or biologically active compounds. 67,68,[156][157][158][159][160] To systemise the results in this section, the information is ordered according to the hydrosilylation of conjugated 1,3diynes, 1,n-diynes, as well as the formation of various products, 1,3-enynes, allenes, polymers, or cyclic compounds.…”

Asymmetric Cobalt‐Catalyzed Regioselective Hydrosilylation/Cyclization of 1,6‐Enynes

“…[8b] Considering complete lack of chiral catalysts for asymmetric hydrosilylation/cyclization of 1,6-enynes to synthesize enantioenriched cyclic alkylsilanes,w eb ecome particularly interested in identifying chiral cobalt catalysts for the synthesis of such chiral cyclic alkylsilane compounds during our continuous effort in developing cobalt-catalyzed hydrosilylation reactions of unsaturated hydrocarbons. [11] Herein, we report cobalt-catalyzed asymmetric hydrosilylation/cyclization of 1,6-enynes that yields chiral alkylsilane or vinylsilane products with excellent enantioselectivity.W ea lso showed that chiral organosilane products from these reactions can be converted to avariety of chiral heterocyclic compounds via stereospecific transformations of either SiÀHorCÀSi bonds.Mechanistic studies reveal the chelation of 1,6-enynes to cobalt catalysts and the factors that control the regioselectivity of this cobalt-catalyzed hydrosilylation/cyclization of 1,6-enynes.…”