Synthesis of new C2-symmetrical diphosphines using chiral zinc organometallics

✍ Scribed by Alexia Longeau; Sandrine Durand; Anja Spiegel; Paul Knochel

• Publisher: Elsevier Science
• Year: 1997
• Tongue: English
• Weight: 217 KB
• Volume: 8
• Category: Article
• ISSN: 0957-4166
• DOI: 10.1016/s0957-4166(97)00052-9

✦ Synopsis

The new C2-symmetrical diphosphines 1--4 of potential interest for asymmetric catalysis were prepared in protected form by a convergent synthesis based on the use of readily available (S,S)-l,2-cyciohexanedicarboxylic acid 8 and the phosphorus reagent (Et2N)2PLi.BH 3. (~) 1997 Elsevier Science Ltd Chiral diphosphines are an important class of ligands for the performance of metal complexes catalyzed asymmetric transformations. ] C2-Symmetrical diphosphines 2 are especially interesting ligands. After complexation to a metal center, two homotopic space regions are defined so that the coordination of a reagent from the top or the bottom face leads to the same chiral intermediate. Recently, we have developed new general synthetic methods for the preparation of polyfunctional and chiral phosphines involving electrophilic phosphorus reagents (R3_nPCln) 3 and nucleophilic phosphorus reagent ((Et2N)2PLi.BH3). 4 Herein, we wish to report the application of these methods to the preparation of the new C2-symmetrical diphosphine-borane complex 1 as well as some related phosphine-borane complexes 2, 3 and 4 (Scheme 1).