Mannich-type products

The reaction of chiral aldimines with 2-silyloxybutadienes in the presence of triflic acid affords novel Mannich-type products with high diastereoselectivity986 [Eq. (5.357)]. 

Attempted Knoevenagel Reaction Gives Mannich-Type Products... 

Attempted Knoevenagel condensation of the coumarin aldehydes 1 using piperidine as base led in a number of cases to formation of significant amounts of Mannich-type products 2 (R2,R3 =... 

A zinc-bis(BINOL) complex has been employed to effect chemoselective enolate formation from an a-hydroxy ketone (in the presence of an isomerizable imine) to give a Mannich-type product in high ee 1... 

The phosphoric acid is expected to promote the substitution reaction as a result of its dual function (Figure 3.3a). Intracomplex deprotonation from B by the basic phosphoryl oxygen would allow the direct substitution of diazoacetate, giving a Mannich type product without the formation of aziridine products. 

Aminobenzylation of phenols. Sodium phenolates react with these reagents to furnish Mannich-type products. 

Ishihara developed a highly efficient Mukaiyama aldol reaction between ketones and trimethylsilyl enolates catalysed by sodium phenoxide-phosphine oxides (46) as simple homogeneous Lewis-base catalysts (0.5-10 mol%) (Scheme 2.29). For a variety of aromatic ketones and aldimines, aldol and Mannich-type products with an a-quaternary carbon centre were obtained in good to excellent yields. Remarkably, a retro-aldol reaction was not observed. On a scale of up to 100 mmol, benzophenone and trimethylsilyl enolate gave the product in 97% yield (34.8 g) using 0.5 mol% of catalyst. 

Inorganic complexes have been found to work as efficient pboto-catalysts for further oxidative coupling reactions. As an example, Mannich type products have been obtained in good to excellent yields. ... 

Zhao G, Yang C, Guo L, Sun H, Chen C, Xia W (2012) Visible light-induced oxidative coupling reactirui easy access to Mannich-type products. Chem Coimnim 48 2337-2339... 

Enantioenriched aziridines are important building blocks for the synthesis of functionalized chiral amines such as amino acid derivatives and hgands. In 2(X)8, Hashimoto et al. reported an axially chiral dicarboxyUc acid (66a)-catalyzed asymmetric aziridination of IV-Boc intines 64 with diazoacetantides 65, which resulted in trans-selective aziridine products 67 with up to 99% ee (Scheme 2.19) [30a]. The use of diazoacetantide 65 instead of diazoacetate as nucleophiles could lower the acidity of the a-proton of diazo carbonyls, thus leading to the formation of aziridine other than Mannich-type products. With this success, the same group recently established the asymmetric construction of... 

Synthetically important chiral 1-monosubstituted 1,3-diamines (145) are synthesized in Mannich-type reactions of enecarbamates (140) with aromatic and aliphatic hemiaminal ethers (141) in the presence of phosphoric acid 95a. This process involves the highly reactive Mannich-type product (144), which is entrapped by a methanol molecule generated during the formation of the imine (143) derived from the hemiaminal ether (141) (Scheme 28.15) [72]. Similarly, diastereo- and enantio-enriched o ti-l,2-disubstituted 1,3-diamines are prepared by the Mannich-type reaction of aldehydes, anilines, and enecarbamates in the presence of chiral phosphoric acid [73]. 

Another pioneering study [16] by the Dixon group, published in 2006, involved the addition of malonates to carbamate-protected imines (Scheme 6.6). Using the cinchonine-derived thiourea catalyst 32, the Mannich-type products were obtained in good to excellent enantioselectivity and good yields. 

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