Rhodium-Catalyzed Asymmetric Rearrangement of Alkynyl Alkenyl Carbinols:  Synthetic Equivalent to Asymmetric Conjugate Alkynylation of Enones

Abstract

Asymmetric 1,3-rearrangement of an alkynyl group of alkynyl alkenyl carbinols giving β-alkynylketones took place in high yields with high enantioselectivity in the presence of a hydroxyrhodium/(R)-binap catalyst. The present method including a key β-alkynyl elimination step in the catalytic cycle is synthetically equivalent to the asymmetric conjugate addition of terminal alkynes to β-substituted enones.

Selektive C‐C‐Bindungsspaltung zur stereoselektiven Synthese acyclischer Systeme

“…Das hierbei in situ erzeugte Enon befindet sich während dieser Transformation in direkter Nähe zum Metallatom, was letzten Endes die Alkinylierung durch die Organorhodiumspezies ermçglicht (Schema 28). [85] Schema 29 zeigt, dass a,a-disubstituierte Arylmethanole in der Lage sind, mit Arylbromiden, mittels einer Palladiumkatalysierten Fragmentierung der C(sp 2 )-C(sp 3 )-Bindung, zu reagieren. [86] Diverse andere Systeme sind ebenfalls in der Lage, nach einer Fragmentierung der Kohlenstoff-Kohlenstoff-Bindung reaktive Intermediate zu bilden.…”

Synthetic Chemistry with an Eye on Future Sustainability

“…Trost et al pioneered a palladium-catalyzed conjugated direct addition of terminal alkynes to electron-deficient alkynes [71]. Highly efficient, direct, and asymmetric conjugated additions of terminal alkynes to electron-deficient alkenes have been developed more recently [72]. Further, direct addition of terminal alkynes to aldehydes was reported by Yamaguchi et al [73], Han and Huang [74], and Carreira et al [75].…”

Combining NHC–Cu and Brønsted Base Catalysis: Enantioselective Allylic Substitution/Conjugate Additions with Alkynylaluminum Reagents and Stereospecific Isomerization of the Products to Trisubstituted Allenes

“…[11] 3) Catalytic EAS with alkenes possessing the suggested substitution pattern have been less widely investigated [12] and provide a challenge in reaction efficiency and/or enantioselectivity (vs. variants that afford quaternary carbons or disubstituted olefins [9] ). 4) Carboxylic esters and derivatives would allow for exploration of the influence of electronic effects and a chelating Lewis basic group on the catalytic EAS and the subsequent alkyne-to-allene interconversion.…”