Chele‐ und Anticheleselektivität, V [1] . Über die Struktur und Chemoselektivität einiger Übergangsmetall‐Derivate von Carbonsäureestern
1994; Wiley; Volume: 127; Issue: 11 Linguagem: Inglês
10.1002/cber.1491271129
ISSN0009-2940
AutoresThomas Kauffmann, T. Möller, Heinz‐Wilhelm Wilde,
Tópico(s)Organometallic Complex Synthesis and Catalysis
ResumoChele‐ and Anti‐cheleselectivity, V [1] . ‐ On the Structure and Chemoselectivity of Some Transition Metal Derivatives of Carboxylic Acid Esters On account of the IR spectra of EtO 2 CCH 2 FeCl ( 2a ), EtO 2 CCH 2 CoCl ( 3a ), and EtO 2 CCH(Et)CoCl ( 3b ), prepared in situ by transmetalation of the corresponding Li enolates, and EtO 2 CCH(Et)CrCl 2 ( 5b ), obtained in situ by one‐electron oxidative addition of EtO 2 CCH(Et)Br to CrCl 2 , it is assumed that these and similar complexes ( 2b, 2c, 3c ) form 8‐membered cyclic dimers of type 11 in THF in analogy to the Reformatzky reagents. Representatives of these complexes and of corresponding Ti complexes were treated (THF, mol ratio 1:1:1) with substrate pairs, consisting of a normal ketone and a ß‐functionalized ketone (Table 2) or alternatively of a normal ketone and an α‐functionalized ketone (Table 3). In the first case high anti‐cheleselectivity was observed, but in the second case high cheleselectivity. The reasons for this different behaviour are discussed.
Referência(s)