A Highly Enantioselective Catalyst for the Asymmetric Nozaki–Hiyama–Kishi Reaction of Allylic and Vinylic Halides

Abstract

Katalytische asymmetrische Additionen von Vinylhalogeniden und ‐triflaten an Aldehyde (Nozaki‐Hiyama‐Kishi‐Reaktion) mit beträchtlicher Stereoinduktion wurden erstmals mithilfe des Salen‐artigen Liganden (S,S)‐1 erreicht (siehe Schema; PMB=para‐Methoxybenzyl), der sich durch ein endo,endo‐2,5‐Diaminonorbornan‐Gerüst auszeichnet. Die Enantioselektivitäten betragen, bei hohen Ausbeuten, bis zu 92 % ee.

Chromium‐Catalyzed Pinacol‐Type Cross‐Coupling: Studies on Stereoselectivity

“…[20] As neither variation of the solvent nor the use of chromocenes had led to higher diastereoselectivities with acceptable yields of pinacols, we tried other ligands while keeping DMF as solvent. Only a few other examples of enantioselective catalytic NozakiHiyama reactions have been reported, [22][23][24] and so we tried different complexes of ligands 16-19, prepared either in situ or separately from the ligand, chromium(ii) chloride, and triethylamine.…”

Application of Tridentate Bis(oxazoline) Ligands in Catalytic Asymmetric Nozaki–Hiyama Allylation and Crotylation: An Example of High Enantioselection with a Non‐Symmetric Bis(oxazoline) Ligand

“…Berkessel employed the salen derivative [(S,S)-DIA-NANE] 4 and obtained higher enantiodiscrimination in the reaction of benzaldehyde with allyl bromide (90% ee) than with allyl chloride (79% ee). [11] Oxazoline-containing ligands have also been used with some success in the enantioselective Nozaki-Hiyama À Kishi reaction. The chromium(III)/sulfonamideoxazoline ligand complex 5 gave good enantioselectivities for the Ni/Cr-mediated alkenylation and the Co/Crmediated alkylation of aliphatic aldehydes and was thus applied by Kishi in the synthesis of the C 14 -C 26 segment of halichondrins.…”

New Proline–Oxazoline Ligands and Their Application in the Asymmetric Nozaki–Hiyama–Kishi Reaction

“…Two such examples are the total synthesis of palytoxin and halichondrin B, which both involve extensive use of chromium additions. [15] To date there has been a limited range of ligand classes applied to the enantioselective process, with the most promising examples emerging from the groups of Sigman (3), [5] Cozzi and Umani-Ronchi (11), [16] Nakada (12, 13), [17] Berkessel (14), [18] Kishi (15) [19] and ourselves (4) [8,9] (Figure 5). Our new ligand class 5 was applied in the chromiumcatalysed reaction of allyl bromide with benzaldehyde (Table 1).…”