l-Prolinal Dithioacetal: A Highly Effective Organocatalyst for the Direct Nitro-Michael Addition to Selected Cyclic and Aromatic Ketones

Abstract

The synthesis of novel l-prolinal dithioacetal and its application as an organocatalyst for the direct Michael addition of cyclic ketones and acetophenone derivatives to trans-β-nitrostyrene and related compounds is described. The prolinal dithioacetal acts as effective catalyst in the case of cyclic ketones of different ring size, in particular five- and six-membered examples, as well as larger and smaller ring systems. High enantioselectivity and diastereoselectivity is observed for different substrates and trans-β-nitrostyrenes. Also, the first asymmetric syntheses of selected 2-methyl-4-nitro-1,3-diphenylbutan-1-one derivatives by application of the obtained organocatalyst is presented.

The Asymmetric Buchwald–Hartwig Amination Reaction

“…Axial chirality has been arising wide range of interests in recent years due to its important application in natural products, materials and asymmetric catalysis. [41,42] Transition metal mediated asymmetric synthesis is one of the important approaches to construct axial chirality. [43][44][45][46][47][48][49] The asymmetric Buchwald-Hartwig reaction was successfully used to synthesize atropisomers with excellent stereogenic control (Scheme 10).…”

“…Axial chirality has been arising wide range of interests in recent years due to its important application in natural products, materials and asymmetric catalysis [41, 42] . Transition metal mediated asymmetric synthesis is one of the important approaches to construct axial chirality [43–49] .…”

A tribute to Professor Zbigniew Czarnocki

“…Surprisingly, it was not only useful for the Suzuki coupling, but also proved to be quite efficient in the stereoselective aldol reaction serving as an organocatalyst (Figure 5). 18 Stereoselective synthesis of lignans The Czarnocki's group also presented a general method for diastereoselective synthesis of cyclolignans. The synthetic sequence started with a double Stobbe condensation of the succinate ester and appropriate aromatic aldehydes.…”

Recent Advances in Synthesis of Multiply Arylated/Alkylated Pyridines

“…Accordingly, there are review articles describing the regioselective synthesis of 2,4,6-triaryl pyridines and atropisomerism studies of selected arylpyridines. [16,22] Regarding the synthesis of multiple arylated/alkylated pyridines, these frameworks sometimes appear in the literature as a part of products; however, there is no concise review article. This knowledge gap prompted us to collate recent advances in the synthesis of tri-, tetra-, and penta-aryl/alkyl pyridines with categorization based on the reaction pattern: condensation, cycloaddition, Suzuki-Miyaura cross-coupling, and ring transformation.…”

“…Direct arylation/alkylation is not feasible, as explained earlier, and the other two strategies are not always applicable because the aryl and alkyl groups do not exert any significant electronic influence on substrate activation. Hence, introducing the desired aryl/alkyl group at the desired position remains is difficult [16] . In particular, substituting different aryl or alkyl groups at multiple positions in the pyridine framework remains an enticing project.…”