21388-29-4Relevant academic research and scientific papers
Halogenated biphenyl-2,2'-diylbisdiphenylphosphines, their preparation and their use
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, (2008/06/13)
Compounds of the formula I STR1 in which the phenyl rings of the biphenyl molecule can be substituted with up to 8 fluorine and/or chlorine atoms are suitable as catalysts.
Efficient synthesis of (R)- and (S)-(6,6'-difluorobiphenyl-2,2'-diyl) bis(diphenylphosphine); Electron-poor biphenyl-type ligands for transition metal catalysts
Jendralla,Chang Hua Li,Paulus
, p. 1297 - 1320 (2007/10/02)
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).
