Copper‐Catalyzed Asymmetric Conjugate Addition of Trialkylaluminium Reagents to Trisubstituted Enones: Construction of Chiral Quaternary Centers

Abstract

Me3Al, Et3Al, and vinylalane species undergo enantioselective conjugate addition to a wide range of 2- or 3-substituted enones (cyclopent-2-enones, cyclohex-2-enones, 3-methyl cyclohept-2-enone) in the presence of catalytic amount of copper salt (copper thiophene carboxylate, [Cu(CH3CN)4]BF4 or [CuOTf]2C6H6) and tropos-phosphoramidite-based ligand. Thus, chiral quaternary centers can be built, with up to 98% ee after rigorous optimization of experimental conditions. It was shown that the main important parameter was the order of the introduction of the reagents. Then, the generated enantioenriched aluminium enolates and the chiral conjugate adducts were functionalized and used for subsequent reactions.

Chemoselectivity as a Delineator of Cuprate Structure in Catalytic 1,4‐Addition of Diorganozinc Reagents to Michael Acceptors

“…The following compounds were attained by literature procedures: 1 a, [11] 1 b, [12] L A , [17] 2 a, [14] 11, [12] and L D . [23] Alternative preparation of 1 b-c 2-Formyl-1,3-dithiane (2 a): [14] To a flame-dried flask containing 1,3-dithiane (2.50 g, 20.8 mmol) in dry THF (50 mL) at À30 8C nBuLi (14.0 mL, 1.6 m in hexane, 22.4 mmol) was added and the reaction mixture was stirred at this temperature for 1 h. The mixture was allowed to come to À10 8C and dry N,N-dimethylformamide (560 mL, 7.21 mmol) was added. The mixture was stirred for 2 h at À10 8C before warming to 0 8C and overnight stirring at room temperature.…”

Et3B-mediated and palladium-catalyzed direct allylation of β-dicarbonyl compounds with Morita–Baylis–Hillman alcohols

“…In a previous report, Alexakis and co-workers have demonstrated that copper-catalyzed conjugate addition of Grignard reagents onto α-methyl cyclic enones, affording mainly the trans -2,3-disubstituted cyclohexanones as being the thermodynamic products [52]. Similarly, we believe that the intramolecular conjugate addition of carbanion 3j onto α-substituted enone moiety is under thermodynamic control, leading to the tricyclic compound 6j , in which the two hydrogens H 2 and H 3 , are on a trans -ring junction whereas the second ring junction is cis (Fig.…”

Scalable Route to Chiral Phosphoramidites

“…The second reaction, formation of phosphoramidite 3, was reported to proceed in THF (Vuagnoux-d'Augustin et al;www.ccsenet.org/ijc International Journal of Chemistry Vol. 8, No.…”

“…A series of chiral ligands have been prepared, particularly the preparation of ligand 3 has been described in the literature (Vuagnoux-d'Augustin et al;2007) and is shown in Scheme 1. This ligand was used in the copper mediated asymmetry-inducing step in a production of taxadienone (Mendoza et al, 2012).…”