Regioselective addition of DDQ on a quinoid ring: an entry into chiral zwitterionic bridging ligands
Abstract
The regioselective insertion of DDQ into a C-H bond of the 6π + 6π electron zwitterionic benzoquinonemonoimines 4a-c results in the formation of the novel chiral C-substituted quinoid ligands 11a-c. These Michael adducts feature a preserved zwitterionic form and a quaternary stereogenic carbon center as evidenced by the single crystal X-ray structure of the derivative 11a. The ECD spectra, optical rotations and racemization barriers of the two enantiomers of 11a were measured subsequently to their separation by a preparative chiral HPLC. Because the racemization of 11a is stopped in basic media, compounds 11a-c give a new entry in chiral zwitterionic bridging ligands.
Domains
Coordination chemistryOrigin | Files produced by the author(s) |
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