Capping methodology in cyclodextrin chemistry: use of a symmetrical diketone reagent for regiospecific installation of unsymmetrical imine-enamine and imidazole caps.
Methylated α- and β-cyclodextrin skeletons were both equipped with an unsymmetrical N-(2-N-alkylaminoacenaphthenyl)alkylimine rigid handle. The capping reaction, which consists of condensing a diaminocyclodextrin with highly symmetrical acenaphthenequinone, was found to be regiospecific when starting from cyclodextrin-diamines without any symmetry element. All modified cyclooligosaccharides have intra-annular nitrogen donor atoms. They undergo further cyclization on oxidation, whether chemically with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone or electrochemically, to give highly strained cyclodextrins capped with an unsymmetrical 1,2-disubstituted 1H-imidazole unit.
Laboratoire de Chimie Inorganique Moléculaire et Catalyse, Institut de Chimie UMR 7177 CNRS, Université de Strasbourg, 1 rue Blaise Pascal, 67008 Strasbourg CEDEX (France).
Matthieu
M
Jouffroy
Dominique
D
Armspach
Alain
A
Louati
Dominique
D
Matt
Loïc
L
Toupet
cavitands; copper; cyclization; cyclodextrins; regioselectivity