1. Chiral phosphaalkene-oxazoline ligands for the palladium-catalyzed asymmetric allylic alkylation
Julien Dugal-Tessier, Gregory R Dake, Derek P Gates Org Lett. 2010 Oct 15;12(20):4667-9. doi: 10.1021/ol1020652.
Enantioselective catalysis in moderate to excellent yields and ee's has been accomplished using a phosphaalkene-based ligand system. Specifically, the palladium-catalyzed allylic alkylation of 1,3-diphenyl-2-propenyl acetate using a chiral P(sp(2)),N(sp(2)) ligand proceeds with a variety of malonate nucleophiles in 73-95% yield (79-92% ee).
2. Synthesis of amino acid derivatives via enantio- and diastereoselective Pd-catalyzed allylic substitutions with a non-stabilized enolate as nucleophile
Thomas D Weiss, Günter Helmchen, Uli Kazmaier Chem Commun (Camb). 2002 Jun 21;(12):1270-1. doi: 10.1039/b203791m.
Diastereomer ratios of up to 95:5 and enantiomeric excesses of up to 95% were achieved in Pd-catalyzed asymmetric alyllic substitutions with zinc enolates of glycine esters as nucleophiles; a remarkable effect of the ligand on the diastereoselectivity of the substitution was found.
3. Chiral phosphine-free Pd-mediated asymmetric allylation of prochiral enolate with a chiral phase-transfer catalyst
M Nakoji, T Kanayama, T Okino, Y Takemoto Org Lett. 2001 Oct 18;3(21):3329-31. doi: 10.1021/ol016567h.
[reaction: see text]. A chiral phase-transfer catalyst has been applied to the asymmetric allylation of the tert-butyl glycinate-benzophenone Schiff base with various allylic acetates for the first time to give the allylated products in good yields and with comparable to higher enantioselectivity than for asymmetric alkylation at the same temperature (91-96% ee) without any chiral ligands for coordinating to the palladium.
