Asymmetric Synthesis of Succinic Semialdehyde Derivatives

The nucleophilic Michael addition of 2-(diphenylmethoxymethyl)-1-methyleneamino pyrrolidine 1D
to prochiral aliphatic and aromatic alkylidene malonates 2 takes place in the presence of MgI2 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 BF3·OEt2-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.