| Popis: |
Racemic title compound (RS)- 5 is synthesized (Scheme 1 , 100g scale) in four simple steps (49% overall yield) from meta-fluorobromobenzene 1 . (RS)- 5 is efficiently resolved (Scheme 2) utilizing commercial (S)-(+)-dipalladium complex 9 to give homochiral (S)-(+)- 5 and (R)-(−)- 5 in 75 and 95% of theoretical yield , respectively. Enantiomerically pure diphosphines (S)- 5 and (R)- 5 do not racemize in organic solutions, even when heated to 207°C. Homochiral palladium (II) dichloride complexes (−)- 11 and (+)- 11 are prepared in quantitative yield. In situ rhodium(I)-complex of homochiral 5 is an efficient catalyst for alkene - hydroboration by catecholborane and requires high hydrogen pressure to catalyze hydrogenation. Interesting anomalies of the specific rotation are observed for homochiral diphosphines (S)-(+)- 5 and (R)-(−)- 5 . The specific rotation [α]D 25 of (S)-(+)- 5 measured in similar aromatic hydrocarbons (toluene , o-xylene, mesitylene, tetralin) varies from +114.9 (c 0.99 , toluene) to −73.9 (c 0.46. tetralin). |
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