Conformational preference and remote (1,10) stereocontrol in biphenyl-2,2'-dicarboxamides.
The double ortholithiation and electrophilic quench of N,N,N'N'-tetraisopropylbiphenyl-2,2'-dicarboxamide 1 is diastereoselective, giving the chiral, C(2)-symmetric atropisomers of the 3,3'-disubstituted products 3. These chiral atropisomers can be converted with moderate to good stereoselectivity to their achiral, centrosymmetric epimers by heating. The stereoselectivity of the double lithiation-quench reaction is determined by the stereochemistry of the intermediate doubly lithiated species 2, either diastereoisomer of which may be formed stereospecfically from the corresponding atropisomeric dibromo compounds.[reaction: see text]
Clayden
J
J
Department of Chemistry, University of Manchester, Oxford Road, Manchester M13 9PL, U.K. j.p.clayden@man.ac.uk
Lund
A
A
Youssef
L H
LH