Enantioselective synthesis of aziridine 2,2-dicarboxylates. Part I: Copper(II)-bisoxazoline complex-catalysed Michael reaction on alkylidene malonates

Enantiopure Fluorous Bis(oxazolines): Synthesis and Applications in Catalytic Asymmetric Reactions

Various enantiopure fluorous bis(oxazolines) with fluorine content between 52.7 and 58.7% have been synthesized by a simple reaction sequence that involved the introduction of two fluorinated ponytails by alkylation of the corresponding nonfluorous bis(oxazolines). These new ligands have been used in palladium-catalyzed alkylation of rac-(E)-1,3-diphenylpropenyl acetate with carbon nucleophiles and in copper-catalyzed oxidation of cycloalkenes; these ligands exhibited enantioselectivities up to 98 and 77%, respectively, quite close to the values obtained using the analogous nonfluorous bis(oxazolines). These ligands could be easily recovered by liquid-liquid extraction or solid-liquid separation and reused with the same enantioselectivities.

Asymmetric synthesis of succinic semialdehyde derivatives

The nucleophilic Michael addition of 2-(diphenylmethoxymethyl)-1-methyleneamino pyrrolidine 1Dto prochiral aliphatic and aromatic alkylidene malonates 2 takes place in the presence of MgI(2) to afford the corresponding Michael adducts 3 in excellent yields and good selectivities. In the aromatic series, optically pure (de > 98%) major diastereomers (S,S)-3 were isolated in good yields (77-93%) after chromatographic separation. Direct, racemization-free BF(3).OEt(2)-catalyzed thiolysis of compounds 3 afforded dithioacetals 7. These compounds were transformed into malonates 8 and succinic semialdehyde derivatives 9 by Raney Nickel mediated desulfuration or decarboxylation, respectively.