Nitroalkenes intermolecular Stetter

Rovis and co-workers have also extended the intermolecular Stetter reaction to inclnde nitroaUcenes as the electrophilic component. Fluorinated triazolinm precatalyst 155 was effective in catalysing the reaction of a variety of heteroaromatic aldehydes 153 with nitroalkenes 154 to generate P-nitroketones in excellent yields and enantioselectivities. The authors propose that stereoelectronically induced conformational effects on the catalyst skeleton are key to the high selectivities observed with flnorinated catalyst 155 (Scheme 12.33) [69],... 

DiRocco DA, Oberg KM, Dalton DM, Rovis T (2009) Catalytic asymmetric intermolecular Stetter reaction of heterocyclic aldehydes with nitroalkenes backbone fluorination improves selectivity. J Am Chem Soc 131 10872-10874... 

Scheme 7.29 NHC-catal3 ed asymmetric intermolecular Stetter reaction of heteroaromatic aldehydes with p-alkyl substituted nitroalkenes...

Scheme 7.30 NHC-catalyzed asymmetric intermolecular Stetter reaction of enals with p-substituted nitroalkenes reported by Rovis.

In 2009, a highly enantioselective intermolecular Stetter reaction of het-eroaiylaldehydes with nitroalkenes was developed by Rovis and coworkers. ... 

In 2009, Rovis and co-workers [54] developed the chiral NHC catalyzed intermolecular Stetter reaction of heteroarylaldehydes with nitroalkenes. In the presence of 10 mol% of chiral fluorine-modified triazolium salt 44, the desired products were obtained in very good yields with high enantioselectivities (Scheme 7.34). Recently, they successfiilly expanded the reactions to enals. It was foimd that protic solvents are required for the reactivity. In addition to cinnamic aldehyde derivative, (3-alkyl enals also worked well to give the adduct in good yields with good enantioselectivities (Scheme 7.35) [55]. 

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