Organocatalytic asymmetric fluorination of α-chloroaldehydes involving kinetic resolution

• Kazutaka Shibatomi,
• Takuya Okimi,
• Yoshiyuki Abe,
• Akira Narayama,
• Nami Nakamura and
• Seiji Iwasa

Beilstein J. Org. Chem. 2014, 10, 323–331, doi:10.3762/bjoc.10.30

• determination of the absolute stereochemistry of a resulting α-chloro-α-fluoroaldehyde. Some information about the substrate scope and a possible reaction mechanism are also described which shed more light on the nature of this asymmetric fluorination reaction. Keywords: α-branched aldehyde; asymmetric

• -chloroaldehydes, a type of α-branched aldehyde, mediated by the Jørgensen–Hayashi catalyst 1 [8]. The reaction yielded the desired α-chloro-α-fluoroaldehydes with high enantioselectivity when the starting aldehyde was used in excess over N-fluorobenzenesulfonimide (NFSI) in the reaction. However, when an excess

• to chlorofluoro alcohol 4a. Proposed reaction mechanism. Fluorination of the enantiomers of 2a. Enantioselective fluorination of α-branched aldehyde 12. Enantioselective fluorination of α-chloroaldehydes.a Acknowledgements This study was supported by the Tatematsu Foundation and a Grant-in-Aid for

N-Heterocyclic carbene-catalyzed direct cross-aza-benzoin reaction: Efficient synthesis of α-amino-β-keto esters

• Takuya Uno,
• Yusuke Kobayashi and
• Yoshiji Takemoto

Beilstein J. Org. Chem. 2012, 8, 1499–1504, doi:10.3762/bjoc.8.169

• , carbamate, and phenyl groups, were converted into the corresponding products 5l–o in good yields. The α-branched aldehyde, however, failed to give the desired product 5p, presumably due to the increased steric hindrance along with the inherently low electrophilicity. In order to elucidate the reaction