Stereoselective synthesis of 5,6-disubstituted 5,6-dihydro-1,10-phenanthrolines and a rare example of axially constrained 2,2′-bipyridines

The stereoselective synthesis of 5,6-disubstituted 5,6-dihydro-1,10-phenanthrolines and (5S,6S)-5,6-dihydroxy-5,6-dihydro-1,10-phenanthroline cyclic o-xylylene diether, a rare example of an axially constrained 2,2′-bipyridine is reported. The strategy to obtain such compounds is based on two highly efficient reactions, the Sharpless asymmetric dihydroxylation and the Ullmann intramolecular coupling.

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5,6-Hydroxy-5,6-dihydro-1,10-phenanthroline cyclic o-xylylene dietherC16H20N2O2[α]D25=+67.4 (c 0.51, EtOH abs.)Absolute configuration: (5S,6S)Prepared from (1S,2S)-1,2-bis(2-bromopyridin-3-yl)ethane-1,2-diol

5,6-Dihydro-1,10-phenanthroline-5,6-diolC14H14N2O2[α]D25=+1.8 (c 0.076, CHCl3)Absolute configuration: (5S,6S)Prepared from (1S,2S)-1,2-bis(2-bromopyridin-3-yl)ethane-1,2-diol

1,2-Bis(2-bromopyridin-3-yl)ethane-1,2-diolC12H10Br2N2O2[α]D25=+85.4 (c 0.0068, EtOH abs.)Absolute configuration: (5S,6S)Prepared from (E)-1,2-bis(2-bromopyridin-3-yl)ethene