The nucleophylic addition of lithium fluorenyl to an excess of racemic propylene oxide forms bifunctionalized fluorenes (80%). The mixture presents substantial diasteromeric selection with enhancement of the racemic (R,R or S,S) with respect to meso form (R,S) (2.6 : 1). This effect can be ascribed to the identification of the preferred chiral conformation in the intermediate step (scheme 1). The resulting species, having memory of chirality (1) of the first-tethered side arm, adds preferentially the second having homochiral conformation. Spectroscopic features and X-ray crystal structure determination of the racemic, meso and enantiopure forms of 1 will be discussed. The reaction with Cr(CO)3(NCMe)3 and molecular grafting to TiCpCl3 will be also reported. (1). Zhao H.; Hsu D.C.; Carlier P.R. Synthesis 2005, 1, 1-16; J. Gawroński J.; Gawrońska K.; Kwit M.; Kacprzak K.; Rychlewska U. Chirality 2004, 16, 405-413.
New examples of memory of chirality in fluorenyl ligands gem-substituted by alcohol side arms. Coordination to Cr(CO)3 or CpTiCl metal fragments / S. Bordoni; L.Busetto; S. Cerini; M. Monari.. - STAMPA. - (2006), pp. INO-P-02 P.309-INO-P-02 P.309. (Intervento presentato al convegno XXII Congresso Nazionale della Società Chimica Italiana (SCI 2006) tenutosi a Firenze nel 10-9-2006).
New examples of memory of chirality in fluorenyl ligands gem-substituted by alcohol side arms. Coordination to Cr(CO)3 or CpTiCl metal fragments
BORDONI, SILVIA;BUSETTO, LUIGI;CERINI, STEFANO;MONARI, MAGDA
2006
Abstract
The nucleophylic addition of lithium fluorenyl to an excess of racemic propylene oxide forms bifunctionalized fluorenes (80%). The mixture presents substantial diasteromeric selection with enhancement of the racemic (R,R or S,S) with respect to meso form (R,S) (2.6 : 1). This effect can be ascribed to the identification of the preferred chiral conformation in the intermediate step (scheme 1). The resulting species, having memory of chirality (1) of the first-tethered side arm, adds preferentially the second having homochiral conformation. Spectroscopic features and X-ray crystal structure determination of the racemic, meso and enantiopure forms of 1 will be discussed. The reaction with Cr(CO)3(NCMe)3 and molecular grafting to TiCpCl3 will be also reported. (1). Zhao H.; Hsu D.C.; Carlier P.R. Synthesis 2005, 1, 1-16; J. Gawroński J.; Gawrońska K.; Kwit M.; Kacprzak K.; Rychlewska U. Chirality 2004, 16, 405-413.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
