Modular bis(oxazoline) ligands for palladium catalyzed allylic alkylation: unprecedented conformational behaviour of a bis(oxazoline) palladium eta3-1,3-diphenylallyl complex.
New families of enantiopure bis(oxazolines) with 4,5-trans (5 a-g) or 4,5-cis (6 c) stereochemistry at the individual rings have been prepared in high yield. Their eta(3)-allyl palladium complexes (8 a-g, 9 c and 10) have been used as catalytic precursors in allylic alkylation reactions with excellent enantioselectivities (up to 96 %) for the trans oxazoline derivatives, while Pd/6 c system was inactive. NMR studies on palladium eta(3)-1,3-diphenylallyl intermediates (11 a, c and e) showed the presence of syn/syn- and syn/anti-allyl isomers in solution; this resembles the first example of eta(3)-eta(1)-eta(3) isomerism in Pd allylic complexes containing bis(oxazolines) derived from malonic acid.
Pericàs
Miquel Angel
MA
Departament de Química Orgànica, Universitat de Barcelona Parc Científic de Barcelona, Josep Samitier 1-5 08028 Barcelona, Spain.
Puigjaner
Cristina
C
Riera
Antoni
A
Vidal-Ferran
Anton
A
Gómez
Montserrat
M
Jiménez
Francisco
F
Muller
Guillermo
G
Rocamora
Mercè
M