My PhD dissertation - Institut Fresnel
My PhD dissertation - Institut Fresnel
My PhD dissertation - Institut Fresnel
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53<br />
Single-crystal X-ray analysis of pure (-)-45 (Figure 6) [197] afforded the determination<br />
of its absolute configuration which was found to correspond to (M) atropisomer. The dihedral<br />
angle θ (C1A-C6A-C6-C1) was determined to be of 88.3 °, which is, this time, more<br />
comparable to that of BIPHEMP (91 °) or BINAP (87 °) ligands.<br />
Figure 6. Stereoscopic drawing of (M)-(-)-45.<br />
4.4 Dynamic 1 H-NMR Study of Some Biphenyl Substrates<br />
In the course of the previously detailed synthesis, the formation of various<br />
enantiomerically pure 2,2'-dilithiobiphenyls without detectable loss of their optical activity<br />
raised questions about their exact thermal stability towards rotation about the biphenyl single<br />
bond. Since literature data concerning rotational barriers of dilithiobiaryls are somewhat<br />
sporadic and essentially concern binaphthyl units<br />
[55 - 57, 201, ] 202 , some of the dibromobiphenyls<br />
prepared were converted to their dilithio congeners and subjected to dynamic nuclear<br />
magnetic resonance experiments.