My PhD dissertation - Institut Fresnel

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The second phenol ether 36 was finally prepared in a different way than its
homologue 35 since the former procedure only afforded moderate yields (56%). Thus,
biphenol 31 was first deprotonated in tetrahydrofuran using sodium hydride at 25 °C, and then
treated with an excess of ethyl bromide to form 2,2’-dibromo-6,6’-diethoxybiphenyl (36) in
92% yield.
Br
Br
OH
OH
1) NaH (2. 0 eq.), THF, 25 °C
2) C2H 5Br
(2.0 eq.)
Br
Br
O
O
(P)-(-)-31 (P)-(-)-36, 92%
4.2 Preparation of Enantiomerically Pure 6,6’-Dibromobiphenyl-
2,2’-dicarboxylic Acid and Derivatives Thereof
Following the strategy outlined previously, diacid 37 was prepared, starting from the
key intermediate tetrabromobiphenyl 30. The diacid was then resolved into both pure axial
enantiomers and reduced to the corresponding bishydromethyl derivative. Although numerous
ortho,ortho'-diphenic acids have been reported
still to be found on a trial-and-error basis.
[ ] 187 , the most suitable resolution method has
4.2.1 Racemic 6,6’-Dibromobiphenyl-2,2’-dicarboxylic Acid
Biphenol 30 was treated with two equivalents of butyllithium in tetrahydrofuran at
-75°C to produce 2,2'-dibromo-6,6'-dilithiobiphenyl. Subsequent trapping with carbon dioxide
and neutralization afforded 6,6’-dibromobiphenyl-2,2’-dicarboxylic acid (37) in 90% yield.
Br Br
Br Br
30
LiC 4H 9 (2.0 eq.)
THF, - 75 °C
Br Li
Br Li
1) CO 2, THF
2) HCl 10%
Br COOH
Br COOH
rac-37, 90%