Enantioselective addition of diethylzinc to benzaldehyde in the presence of ephedrine derivatives

On the Scope of Trimethylaluminium‐Promoted 1,2‐Additions of ArZnX Reagents to Aldehydes

“…[13] However, at the outset of our investigations no asymmetric 1,2-addition of organozinc halides to aldehydes was known. We aimed to use a promoter to convert the organozinc Abstract: A practical asymmetric 1,2-addition of functionalised arylzinc halides to aromatic and aliphatic aldehydes is described by the use of aminoalcohol catalysis in the presence of AlMe 3 . The process is simple to carry out, uses only commercially available reagents/ligands and provides moderate to good (80-96 % ee) enantioselectivities for a wide range of substrates.…”

“…Since the seminal papers of Oguni (1984, first use of an aminoalcohol ligand), [1] Noyori (1986, first highly enantioselective catalyst), [2] Chaloner (1987, first use of an ephedrinebased ligand) [3] and Soai (1991, first asymmetric use of Phzinc reagents) [4] the addition of ZnR 2 species to aldehydes has become one of the "workhorse" reactions of asymmetric catalysis (Scheme 1). The legions of papers generated by this field are well documented in comprehensive reviews.…”

Dimethylzinc‐Mediated, Enantioselective Synthesis of Propargylic Amines

“…Application of compounds bearing a cyclic amine moiety, (1R,2S)-22 a [35] and (1R,2S)-22 b, [29] provided the product with reduced enantiomeric excess in comparison with (+)-DBNE (entries 3-4). Compounds (1R,2S)-22 c, d, [36,37] with two different substituents on the nitrogen atom, furnished results very similar to that obtained with (+)-NME (entries 5-6 vs entry 1), with the bulkier (1R,2S)-22 c being slightly superior to (1R,2S)-22 d. These results suggest that only one bulky substituent on the nitrogen atom is not sufficient to induce a significant increase in the enantioselectivity of the reaction in comparison with the alkynylation performed with a ligand bearing two small, or unbranched, alkyl substituents on nitrogen.…”

“…All the other analytical data were in agreement with those reported in the literature. [36] General procedure 3 (GP 3): One-pot synthesis of propargylic imines 4 a-e, g Method A (standard conditions): In an oven-dried Schlenk flask under an inert atmosphere of argon were placed p-chlorobenzaldehyde (1 a, 0.056 g, 0.4 mmol) or 2-furfuraldehyde (1 b, 0.038 g, 0.4 mmol) and o-methoxyaniline (2, 0.049 g, 0.4 mmol, 1.0 equiv), followed by anhydrous toluene (4.0 mL). After 30 min stirring, a 2.0 m solution of dimethylzinc in toluene (0.7 mL, 1.4 mmol, 3.5 equiv) was added.…”

Recent Advances in Asymmetric CC and C‐Heteroatom Bond Forming Reactions using Polymer‐Bound Catalysts

“…[150] Soai modified the monomeric chiral ligand with a methylene spacer to give 99% ee in liquid phase. [151] Another ligand used in asymmetric liquid phase 1,2-addition reactions and Diels±Alder reactions is the TADDOL (3a) system.…”