Novel spirobis(oxazo1ines) provide excellent levels of stereocontrol in copper-catalysed Diels-Alder reactions; the larger the ligand bite angle the higher the enantioselection (up to 98.4% ee).

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1996 stereochemistry stereochemistry (general, optical resolution) O 0030 -026The Influence of Ligand Bite Angle on the Enantioselectivity of Copper( II)-Catalyzed Diels-Alder Reactions.-To establish the influence of the title angle different kinds of spirobis(oxazoline) ligands are prepared. In the reaction of (I) with ( II) it is shown that the larger the ligand bite angle the higher the observed enantioselectivity.-(DAVIES, I. W.; GERENA, L.; CASTONGUAY, L.; SENANAYAKE, C. H.; LARSEN, R. D.; VERHOEVEN, T. R.; REIDER, P. J.; Chem.

Concise Synthesis of Conformationally Constrained Pybox Ligands. -Heating of a 15% w/v solution of bisamides such as (III) in BF3· OEt2 offers a straightforward method to prepare title ligands like (IV) , (VI), and (VIII). -(DAVIES, I. W.; GERENA, L.; LU, N.; LARSEN, R. D.; REIDER, P. J.; J. Org. Chem. 61 (1996) 26, 9629-9630; Dep. Process Res., Merck&Co., Inc., Rahway, NJ 07065, USA; EN)