Hoch asymmetrische NHC‐katalysierte Hydroacylierung nichtaktivierter Alkene

Abstract

NHC‐Katalyse, Proto(n)‐Typ: Die Titelreaktion liefert 21 verschiedene Chroman‐4‐on‐Produkte in guten Ausbeuten und mit exzellenten Enantioselektivitäten, jeweils unter Bildung eines quartären Stereozentrums. Auf der Grundlage von DFT‐Rechnungen konnten mögliche Übergangszustände und ein Mechanismus der Stereoinduktion formuliert werden.

Catalytic Asymmetric Intermolecular Stetter Reactions of Enolizable Aldehydes with Nitrostyrenes: Computational Study Provides Insight into the Success of the Catalyst

“…For TS5 the gauche (+) conformation is favored because it is well solvated owing to its large dipole moment. The anti conformation for the Re-face attack is favored [19] because of the stabilizing interaction between the hydrogen of the hydroxy group and the carbon a to the nitro group, [20] favorable electrostatic interactions between the alkyl group of the aldehyde and the nitro group, and because it is well solvated. These combined effects are enough to favor the Re-face attack over the Si-face attack.…”

Asymmetric Synthesis of Highly Substituted β‐Lactones through Oxidative Carbene Catalysis with LiCl as Cooperative Lewis Acid

“…We started our investigations using cinnamaldehyde 1 a and malonate 2 a as substrates. As oxidant, bisquinone 3 15 (1.2 equiv) was chosen and optimizations were conducted using the chiral salts A 16 or B 17 (5 mol %) as NHC precursors. We were pleased to find that with 1,8‐diazabicyclo[5.4.0]undec‐7‐ene (DBU) (1.2 equiv) as a base and A as the catalyst, the reaction proceeded efficiently at room temperature in THF to give lactone 4 aa within 2 h in 84 % yield with complete diastereoselectivity and 48 % enantiomeric excess (Table 1, entry 1).…”

Recent Advances in Organocatalytic Methods for Asymmetric CC Bond Formation

“…Chiral triazolium salt 138 gives rise to excellent yields and enantioselectivity (Scheme 69). [152] Glorius et al also developed a related procedure involving two hydroacylation steps. At first an unsaturated intermediate is formed by intramolecular hydroacylation of an alkine substituted salicylaldehyde.…”

“…applied allyl ether derivatives of salicylaldehydes for the construction of quaternary all‐carbon stereocenters. Chiral triazolium salt 138 gives rise to excellent yields and enantioselectivity (Scheme ) 152…”