Asymmetric 1,4-addition of alkenylzirconium reagents to α,β-unsaturated ketones catalyzed by chiral rhodium complexes

Asymmetric Synthesis of the Epimeric (3S)-3-((E)-Hex-1-enyl)-2-methylcyclohexanones

“…Among several known enantioselective 1,4-additions of organometallic reagents to α,β-unsaturated ketones, we obtained the best results with the recently reported rhodium(I)-catalysed addition of alkenylzirconocene chlorides with BINAP as chiral ligand [3,4]. This result also follows Nicolaou's report of the tandem reaction of the rhodium-catalysed asymmetric additions of alkenylzirconium reagents followed by trapping of the zirconium enolate by aldehydes [5].…”

“…The same coupling in epimer 1b (5.3 Hz) is indicative of a cis-relationship (Figure 1). The absolute configuration was assigned on the basis of the results obtained by Oi and Inoue [3]. 1 H-NMR structural assignment of 1a.…”

“…Both cyclohexanones are being converted to derivatives in which the bicyclic CD-entity is replaced by a single six-membered D-ring and in which the hexenyl substituent serves as a latent aldehyde for the introduction of the A-ring [2]. We describe herein in detail a synthesis of 4a and 4b featuring a highly enantioselective 1,4-addition of alkenylzirconocene to 2-cyclohexenone catalysed by the chiral rhodium complex generated from [Rh(cod)Cl] 2 and (R)-BINAP [3], followed by trapping of the O-enolate with formaldehyde.…”

Rhodium‐ and Palladium‐Catalyzed Asymmetric Conjugate Additions

“…Alkenyl zirconium species, derived from the hydrozirconation [194] of primary alkynes by Schwartz reagent ([Cp 2 Zr(H)(Cl)]), are useful reagents in Rh-catalyzed ECAs [59,195,196]. Aryl-lead [197], -tin [54,57,198], and triarylbismuth [199] compounds are also competent aryl-transfer agents in Rh-catalyzed conjugate additions, even in the presence of air and water [200].…”

Rhodium Catalyzed 1,4-Conjugate Addition of 1,5-Azastibocines with Electron Deficient Olefins

“…11) Inspired by this work, a number of main group compounds were investigated for the transition metal catalyzed 1,4-conjugate addition including organo-aluminum, 12) -boron, 13) -tin, 14) -silicon, 15) -bismuth, 16) -indium, 17) -plumbum, 18) -zirconium 19) and -zinc 20) compounds. Unlike copper reagents, these compounds exhibit a tolerance for hard electrophiles such as water and the reactions can be carried out in an aqueous medium.…”