Diastereoselective [2+2]-cycloaddition reactions of unsymmetrical cyclic ketenes with imines: synthesis of modified prolines and theoretical study of the reaction mechanism.
The synthesis of enantiomerically pure modified proline derivatives was achieved by using spiro beta-lactams as starting material that were prepared in turn by the [2+2]-cycloaddition of unsymmetrical cyclic ketenes with optically active imines. A theoretical study of the [2+2]-cycloaddition reaction, using density-functional methods, gave insights on the origin of the observed stereoselectivity of the Staudinger reaction. The spiro beta-lactams were transformed in the N-Boc derivatives and subjected to nucleophilic ring opening, affording the corresponding enantiomerically pure modified proline derivatives, isolated as orthogonally protected compounds.
Macías
Alberto
A
Departamento de Química Orgánica e Inorgánica, Universidad de Oviedo, Julián Clavería 8, 33006 Oviedo, Spain.
Alonso
Eduardo
E
Del Pozo
Carlos
C
Venturini
Alessandro
A
González
Javier
J
D003500:Cyclization; D005030:Ethylenes / Q000138:chemical synthesis* / Q000737:chemistry; D007097:Imines / Q000737:chemistry*; D007659:Ketones / Q000138:chemical synthesis* / Q000737:chemistry; D008958:Models, Molecular; D008968:Molecular Conformation; D011392:Proline / Q000031:analogs & derivatives* / Q000138:chemical synthesis*; D013237:Stereoisomerism
D005030:Ethylenes; D007097:Imines; D007659:Ketones; D011392:Proline