Cobalt‐Catalyzed One‐Pot Asymmetric Difunctionalization of Alkynes to Access Chiral gem‐(Borylsilyl)alkanes

Abstract

Enantioselective cobalt‐catalyzed one‐pot hydrosilylation and hydroboration of terminal alkynes has been developed employing a cobalt catalyst generated from Co(acac)2 and (R,R)‐Me‐Ferrocelane. A variety of terminal alkynes undergo this asymmetric transformation, affording the corresponding gem‐(borylsilyl)alkane products with high enantioselectivity (up to 98 % ee). This one‐pot reaction combines (E)‐selective hydrosilylation of alkynes and consecutive enantioselective hydroboration of (E)‐vinylsilanes with one chiral cobalt catalyst. This protocol represents the most straightforward approach to access versatile chiral gem‐(borylsilyl)alkanes from readily available alkynes with commercially available cobalt salt and chiral ligand.

Low‐coordinate cobalt(0) N‐heterocyclic carbene complexes as catalysts for hydrosilylation of alkynes

“…[ 1 ] Efforts on this aspect have led to the development of a variety of cobalt catalysts for alkyne hydrosilylation reactions that are useful for the preparation of vinylsilanes. [ 2 ] Representative catalysts of the type include cobalt pyridine imine complexes, [ 3 ] cobalt bipyridine complexes, [ 4 ] cobalt imidazole complexes, [ 5 ] cobalt phosphine complexes, [ 6 ] and cobalt N ‐heterocyclic carbene (NHC) complexes. [ 7 ] Along with the diversity of the ligands in these cobalt catalysts, the oxidation states of the cobalt centers also vary.…”

“…[ 2 ] Indeed, a number of structurally well‐defined cobalt(I) complexes proved robust catalysts for alkyne hydrosilylation reactions. [ 6d,6g,7a ] In contrast to the prevailing use of cobalt (II) and cobalt(I) catalysts, explorations on cobalt(0) catalysts for alkyne hydrosilylation are relatively rare. To our knowledge, the dicobalt carbonyl complexes‐catalyzed reactions reported by Isobe, [ 8 ] Konno, [ 9 ] and Deng [ 7b ] are the only known examples (Figure 1a–c).…”

Enantioselective Cobalt-Catalyzed Hydroboration of Fluoroalkyl-Substituted Alkenes to Access Chiral Fluoroalkylboronates

“…In recent years, base metal catalysts, such as chiral cobalt, 9 iron, 10 and copper complexes, 11 have been employed to catalyze enantioselective hydroboration of 1,1-disubstituted alkenes with HBpin to prepare chiral alkylboronates. During our continuous efforts in developing cobalt-catalyzed asymmetric synthesis of alkylboronates, 12 we became interested in identifying chiral cobalt catalysts for asymmetric hydroboration of simple fluoroalkyl-substituted alkenes to access organoboronates containing fluoroalkyl-substituted stereogenic carbon centers. Migratory insertion of fluoroalkyl-substituted alkenes into metal-hydride and metal-boryl intermediates is a fundamental step in metal-catalyzed hydroboration reactions, and possible ways of migratory insertion of a CF 3 -substituted alkene into Co-H and Co-Bpin bonds are depicted in Figure 1 D. 1,2-Insertion of a CF 3 -substituted alkene into a ( L )Co-H or ( L )Co-Bpin species would generate alkylcobalt intermediates III and IV with fluorine atoms located on their γ-carbon atoms.…”

Recent progress in the chemistry of β-aminoketones

“…31,32 The alternative synthetic routes also involved the direct reductive hydroamination of carbonyl alkynes through the chemo-and regioselective synthesis of enamines with the hydroamination of terminal alkynes under catalytic conditions. [33][34][35][36][37][38] b-Aminoketones were efficiently prepared under mild, green, and catalyzed conditions. [39][40][41] Specically, Mannich reactions were further applied in the synthesis of a variety of adaptable compounds incorporating a b-aminoketone motif in water following green approaches, comprising coumarins, 42 Betti bases, 43 spiro heterocycles, 44 oxindoles, 45 and uorinated aminoketones 46 (Fig.…”