The Enantioselective Allylation and Crotylation of Sterically Hindered and Functionalized Aryl Ketones: Convenient Access to Unusual Tertiary Carbinol Structures

Bestimmte Silberkomplexe katalysieren selektiv entweder die Allenylierung oder asymmetrische Propargylierung von Ketonen. Ohne Ligand entstehen Allenylalkohole als Hauptprodukte, der Zusatz des Liganden Walphos‐8 ergibt enantiomerenangereicherte Homopropargylalkohole. Die Methode kann auf die Umwandlung von prochiralen Diarylketonen in enantiomerenangereicherte tertiäre Diarylalkohole angewendet werden.

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Silver‐Catalyzed Allenylation and Enantioselective Propargylation Reactions of Ketones

Kohn¹,

Ichiishi²,

Jarvo³

2013

“…However, the substrate scope for ketones is generally not satisfactory and furthermore these methods require the use of more than one equivalent of toxic stannanes, which is undesirable with respect to safety and environmental considerations. In recent years, significant advances in ketone allylation have been achieved through the development of catalytic (asymmetric) allylsilylations by using (chiral) copper(I)8 or silver(I)9 Lewis acids 10. Most recently, very elegant, catalytic asymmetric allylborations catalyzed by chiral Lewis11 or Brønsted12 acids have also been reported 13.…”

Section: Examination Of Various Indium Catalysts In the Allylation Ofmentioning

confidence: 99%

Catalytic Activation of Pinacolyl Allylboronate with Indium(I): Development of a General Catalytic Allylboration of Ketones

Schneider

Kobayashi

2007

Hilfe in der Gruppe: Die neuartige Aktivierung eines Gruppe‐13‐Reagens (Bor) durch einen Gruppe‐13‐Katalysator in niedriger Oxidationsstufe (Indium) wurde für die Entwicklung einer allgemeinen katalytischen Allylborierung von Ketonen genutzt. Dieses effiziente C‐C‐Verknüpfungsverfahren ist mit einer Vielzahl an funktionellen Gruppen kompatibel (siehe Schema; B(pin)=Pinacolylboronat).

“…Organozinc compounds have been used for asymmetric additions of alkyl compounds to ketones3 or α‐ketoesters4 and for additions of vinyl,5 alkynyl,2c, 6 or aryl compounds7 to ketones. For allyl addition reactions, the considerably toxic allyl tin compounds have been the commonly used reagents,8 and in fewer cases, allyl silicon2e, 9 or allyl boron compounds10 have been used. In addition to these reagents, organoaluminum compounds are excellent nucleophiles for organic reactions11 owing their high reactivities, a greater Lewis acidity of the aluminum center, and low toxicities.…”

Section: Optimization Of [Alph3(thf)] Additions To 2′‐acetonaphthone mentioning

confidence: 99%

Highly Enantioselective Aryl Additions of [AlAr₃(thf)] to Ketones Catalyzed by a Titanium(IV) Catalyst of (S)‐Binol

Chen

Gau

2007

The asymmetric catalytic C À C bond formation by addition of an organozinc reagent to aldehydes for the synthesis of enantiomerically pure secondary alcohols as building blocks for bioactive compounds has been extensively studied, and numerous catalytic systems have been developed to yield excellent enantioselectivities.[1] Since tertiary alcohols appear in bioactive compounds, [2] the construction of chiral quaternary carbon centers is synthetically important owing to the inertness of ketones toward additions of carbon nucleophiles and less differentiation of the two groups attached to the carbonyl carbon atom. Despite efforts in recent years, only limited examples of catalytic asymmetric additions to ketones have been reported to give excellent stereoselectivities. Organozinc compounds have been used for asymmetric additions of alkyl compounds to ketones [3] or a-ketoesters [4] and for additions of vinyl, [5] alkynyl, [2c, 6] or aryl compounds [7] to ketones. For allyl addition reactions, the considerably toxic allyl tin compounds have been the commonly used reagents, [8] and in fewer cases, allyl silicon [2e, 9] or allyl boron compounds [10] have been used. In addition to these reagents, organoaluminum compounds are excellent nucleophiles for organic reactions [11] owing their high reactivities, a greater Lewis acidity of the aluminum center, and low toxicities. However, the use of organoaluminum compounds in asymmetric catalysis is rare. In the past few years, asymmetric catalytic alkylation, [12] allylation, [13] and alkynylation [14] reactions employing organoaluminum reagents have been established to achieve good to excellent enantioselectivities. Recently, we demonstrated that the novel [AlAr 3 (thf)] reagents are powerful aryl nucleophiles for additions to aldehydes catalyzed by the titanium catalyst of (R)-H 8 -binol (binol = 2,2'-dihydroxy-1,1'-binaphthyl) with the reactions complete in only 10 min. [15] In studies of asymmetric aryl additions to ketones, [7] only a few papers have been reported in just two catalytic systems. The first system is a zinc catalyst of (+)-daib (3-exo-(dimethylamino)isoborneol) with which direct additions of the ZnPh 2 reagent afford phenylation products.[7a] The second system is a series of titanium catalysts of disulfonamides [16] with which additions of ZnPh 2 or aryl zinc reagents furnish phenylation or arylation products. [7b-f] However, generation of aryl zinc reagents from excess ZnEt 2 and aryl boron compounds requires reaction conditions at elevated temperatures for 12-16 h. Furthermore, the arylation reactions have not reached a satisfactory level in yields and stereoselectivities.[7f] To extend applications of [AlAr 3 (thf)] reagents in catalysis, we report herein the first example of asymmetric aryl additions of organoaluminum reagents to ketones. The (S)-binol molecule was selected as the ligand since binol is a remarkable ligand applied to many varieties of asymmetric reactions [17] and since dititanium complexes of binol ligands with known structures [...