Synthesis of Open‐Chain 2,3‐Disubstituted 4‐nitroketones by Diastereoselective Michael‐addition of (E)‐Enamines to (E)‐Nitroolefins. A topological rule for C, C‐bond forming processes between prochiral centres. Preliminary communication

Abstract

The Michael‐additions of aliphatic, alicyclic, and arylsubstituted nitroolefins and enamines lead to γ‐nitroketones 3 in good chemical and excellent (> 90%) diastereomeric yields (see Table 1). The known threo‐configuration of one type of adducts 3 (entries 8, 10, and 11 of Table 1) can be arrived at by assuming the approach 8 of the Michael‐acceptor and ‐donor; the reaction follows a topological rule, which is formulated and which is applicable to such diverse reactions as the diene synthesis, cyclopropanations, carbonyl olefinations and methylenations, aldol‐ and nitroaldol‐type additions, as well as additions of lithium, boron, and chromium derivatives to aldehydes (see 9, 10, 11, and Table 2).

Are Oxazolidinones Really Unproductive, Parasitic Species in Proline Catalysis? – Thoughts and Experiments Pointing to an Alternative View

“…iv) The relative topicity of addition to the enamine C¼C bond follows the topicity rule for the coupling of trigonal centers [45] as shown for the aldol addition in C and for the Michael addition in D, which invariably 35 ) occur with relative topicity lk (Re/Re).…”

Solvent‐Induced Reversal of Enantioselectivity in the Synthesis of Succinimides by the Addition of Aldehydes to Maleimides Catalysed by Carbamate‐Monoprotected 1,2‐Diamines

“…Preliminary studies showed that, as expected, the initial formation of an enamine between catalyst and aldehyde is followed by the nucleophilic attack to the maleimide, according to Seebach's synclinal model (endo attack, Figure 1). [31] A key feature of this model is that the reacting face of the enamine diastereoespecifically attacks only one of the faces of the maleimide. That is, the lower face of the enamine (from our point of view in Figure 1) is reacting with the Re-face of the maleimide, and the upper face of the enamine must react with the Si-face of the maleimide.…”

Asymmetric Conjugate Addition of Ketones to β‐Nitrostyrenes by Means of 1,2‐Amino‐Alcohol‐Derived Prolinamides as Bifunctional Catalysts.

“…The observed linearity suggested that the active catalyst in this process is a monomeric species. [44] The syn-diastereoselectivity and the absolute configuration observed can be reasonably explained through the acyclic synclinal transition state assembly A proposed by Seebach, [45] assuming intramolecular hydrogen bonding (Scheme 8). …”