N-Heterocyclic Carbene-Catalyzed Synthesis of α-Trifluoromethyl Esters.

The N-heterocyclic carbene (NHC)-catalyzed trifluoromethylation of α-chloro aldehydes was developed, allowing straightforward access to valuable α-trifluoromethyl ester derivatives. The unique combination of an electrophilic trifluoromethylation reagent with NHC catalysis was the key for the functionalization of a broad range of α-chloro aldehydes, and the products are formed in moderate to good yields. Investigations of the enantioselective version of this reaction afforded the enantioenriched products in moderate yields with good ee values.

Synthesis of 4-Difluoromethylquinolines by NHC-Catalyzed Umpolung of Imines.

The N-heterocyclic carbene (NHC)-catalyzed umpolung of aldimines for the synthesis of 4-difluoromethylquinoline derivatives is reported. In the presence of NHCs, the intramolecular cyclization of aldimines bearing a moderately electron-poor double bond due to the presence of the -CF3 group likely proceeds via the intermediacy of the aza-Breslow intermediate. The key to the success of this aza-Stetter type transformation is the NHC generated from the bicyclic triazolium salt using DBU as the base.

UV-mediated hydrophosphinylation of unactivated alkenes with phosphinates under batch and flow conditions.

A UV-mediated hydrophosphinylation of unactivated alkenes with H-phosphinates and hypophosphorous acid under radical free conditions is presented. The reaction affords selectively a large number of structurally diverse organophosphorous compounds in moderate to good yields under mild reaction conditions in the presence of an organic sensitizer as catalyst irradiated by UV-A LEDs. Furthermore, the high yielding hydrophosphinylation in continuous flow is disclosed.

Development of a new family of chiral auxiliaries.

A new family of chiral auxiliaries designed on a conformationally restricted version of (-)-8-phenylmenthol has been developed. Both enantiomers are available from an inexpensive synthesis conducted on multigram scale. A first application has showed comparable diastereoselectivity between the novel auxiliary and (-)-8-phenylmenthol.

Synthesis of (phosphonomethyl)phosphinate pyrophosphate analogues via the phospha-Claisen condensation.

Pyrophosphate analogues are of great importance especially for the design of biologically active molecules. The phospha-Claisen condensation allows for the rapid synthesis of (phosphonomethyl)phosphinate pyrophosphate analogues and building blocks that can be employed in numerous applications.

Organocatalytic asymmetric synthesis of sulfoxides from sulfenic acid anions mediated by a Cinchona-derived phase-transfer reagent.

Preliminary results concerning a conceptually novel route to chiral sulfoxides based on the asymmetric alkylation of sulfenate salts with alkyl halides mediated by a chiral phase-transfer catalyst are described. As a representative example, o-anisyl methyl sulfoxide was produced in 96% yield and with an enantiomeric excess of 58% using commercial cinchonidinium derivative 2a.