Catalytic Enantioselective Conjugate Additions of (pin)B‐Substituted Allylcopper Compounds Generated in situ from Butadiene or Isoprene

Abstract

Multicomponent catalytic enantioselective transformations that entail the combination of butadiene or isoprene (common feedstock), an enoate (prepared in one step) and B2(pin)2 (commercially available) are presented. These processes constitute an uncommon instance of conjugate addition of an allyl moiety and afford the desired products in up to 83% yield and 98:2 enantiomeric ratio. Based on DFT calculations stereochemical models and rationale for the observed profiles in selectivity are provided.

Asymmetric Catalytic Formal 1,4‐Allylation of β,γ‐Unsaturated α‐Ketoesters: Allylboration/Oxy‐Cope Rearrangement

“…Compared with L 3 -PiPr 2 ,d erived from S-pipecolinic acid, l-proline-derived L 3 -PrPr 2 and l-ramiprilbased L 3 -RaPr 2 displayed higher activities,y ielding the desired products with 85 and 86 %yields,respectively (entry 5 vs.entries 6and 7). Good yields (67-92 %) with excellent enantioselectivities (92-99 % ee)w ere obtained (entries [10][11][12][13][14][15][16][17][18][19][20][21][22][23]. It was found that the amide units of the ligands showed an appreciable influence on both reactivity and enantioselectivity.W ith less sterically constrained amides (L 3 -RaEt 2 or L 3 -RaPh), both yields and ee values decreased dramatically (entries 8a nd 9).…”

“…[11] Morken and coworkers described the first example of asymmetric catalytic conjugate allylation of allylboronic acid pinacol esters to dialkylidene ketones with the use of either aN i 0 or Pd 0 complex as the catalyst (Scheme 1b). [13] Thef ormation of allyl metal species and metal-p complexation might be the key to delivering a-selective 1,4-addition products.I nc ontrast, allylboronic acids and their esters typically undergo g-addition with aldehydes,k etones,a nd imines to afford homoallylic alcohols and amines. [13] Thef ormation of allyl metal species and metal-p complexation might be the key to delivering a-selective 1,4-addition products.I nc ontrast, allylboronic acids and their esters typically undergo g-addition with aldehydes,k etones,a nd imines to afford homoallylic alcohols and amines.…”

Tertiary α‐Silyl Alcohols by Diastereoselective Coupling of 1,3‐Dienes and Acylsilanes Initiated by Enantioselective Copper‐Catalyzed Borylation

“…[8][9][10] The groups of Marek [8] and Chan [9] reported zinc-promoted alkynylations of acylsilanes with terminal alkynes as pronucleophiles (Scheme 1, top). [12][13][14][15][16][17][18][19] By this method, densely functionalized boron compounds are made available with high levels of regio-and stereocontrol. [10] Based on Itos [11a] and Miyauras [11b] seminal work on the catalytic generation of copper-based boron nucleophiles,their addition across p-systems followed by coupling of the copper intermediate with an impressive variety of electrophiles has recently flourished.…”

New C2-symmetric six-membered carbene ligands for asymmetric diethylzinc addition of arylaldehydes

“…Moreover, the same ligand 3 was proved to be an excellent ligand in multicomponent catalytic enantioselective transformations. 24 With similar starting materials, Wilhelm's group prepared several new tridentate NHC precursors 4 as ionic liquids, [25][26] and these salts were also used as catalyst in asymmetric diethylzinc addition to arylaldehydes, giving the corresponding secondary alcohols in good yields and moderate ees (up to 66%). …”