Enantioselective Cyanosilylation of Alkynyl Ketones Catalyzed by Combined Systems Consisting of Chiral Ruthenium(II) Complex and Lithium Phenoxide

Abstract

Asymmetric cyanosilylation of alkynyl ketones with the catalyst systems consisting of amino acid/2,2′‐bis(diphenylphosphino)‐1,1′‐binaphthyl (BINAP)/ruthenium(II) complex and lithium phenoxide (Ru⋅Li cat.) was studied. The reaction was conducted in tert‐butyl methyl ether (TBME) at −78 °C with a substrate‐to‐catalyst molar ratio (S/C) as high as 2000. A series of simple and functionalized ketones was converted into the alkynyl tertiary cyanohydrin derivatives in up to 99% ee. Appropriate selection of an amino‐acid ligand of the catalyst according to the substrate structure was crucially important to achieve high enantioselectivity and a wide scope of substrates. Transformation of the chiral cyanohydrin product into a functionalized lactone was also examined.magnified image

Waste-Minimized Cyanosilylation of Carbonyls Using Fluoride on Polymeric Ionic Tags in Batch and under Continuous Flow Conditions

“…Therefore, catalytic methods are more commonly applied as they provide better results with mild experimental conditions. Several catalysts have been developed for the cyanosilylation of carbonyls, either under homogeneous − or heterogeneous conditions, − along with methodologies for recovering and reusing homogeneous catalysts. , From the sustainability point of view, easily separable solid catalysts are the preferable choice. The heterogeneous catalysts developed for cyanosilylation reactions may tentatively be classified into three major categories: (i) polyoxometalates, − which mainly act as Lewis bases; (ii) metal–organic frameworks − that exert mainly the role of Lewis acids; and (iii) organocatalysts (e.g., supported phosphine and supported ionic liquid-like phase , ).…”

Catalytic Transfer Hydration of Cyanohydrins to α-Hydroxyamides

“…Hydration of cyanohydrins ( 1 ) to α-hydroxycarboxamides ( 2 ) represents a primary target in this field (Figure A­(i)) . Cyanohydrins are readily available through (asymmetric) cyanation of aldehydes or ketones . Further, α-hydroxyamide substructures are found in various bioactive compounds and are easily convertible to α-hydroxyl esters, α-hydroxycarboxylic acids, and acrylic analogs. , The hydration of acetone cyanohydrin by manganese oxide catalyst is used in the industrial production of methyl methacrylates .…”

Ynones in Reflex‐Michael Addition, CuAAC, and Cycloaddition, as Well as their Use as Nucleophilic Enols, Electrophilic Ketones, and Allenic Precursors

“…Reactions of ynones with C nucleophiles (TMSCN,[16a] umpolung of alkynes,[16b] 1,3‐diketones[16c]), or N nucleophiles (amides,[17a] anilines,[17b] aminoindoles,[17c], [17g] methoxylamine,[17d] alkylamines,[17e] sufonylamines[17f] and NH 4 OAC[17h]) will be discussed in this review.…”

“…In 2017, Fang and co‐workers[16b] disclosed a carbene‐catalyzed cyclization of alkynyl 1,2‐diketones (Eq. 28‐1).…”

“…The Singh group[16c] observed an aldol‐cycloisomerization cascade of ynones with 1,3‐diketones, which led to dihydrofurans 29.2 (up to 98 % ee ) (Eq. 29‐1).…”