Tandem organic reactions Asymmetric synthesis

Wack, H., Hafez, A.M. etal (2002) Bifunctional asymmetric catalysis a tandem nucleophile/ Lewis acid promoted synthesis of P-lactams. Organic Letters, 4, 1603-1605 Taggi, A.E., Hafez, A.M., Wack, H. eta/. (2002) The development of the first catalysed reaction of ketenes and imines catalytic, asymmetric synthesis of P-lactams. Journal of the American Chemical Society, 124, 6626-6635 Taggi, A.E., Hafez, A.M., Dudding, T. and Lectka, T. (2002) Molecular mechanics calculations as predictors of enantioselectivity for chiral nucleophile catalysed reactions. Tetrahedron, 58, 8351-8356. 

Lee, S. L, Jang, J. H., Hwang, G.-S., Ryu, D. H. (2013). Asymmetric synthesis of a-aUcylidene-fS-hydroxy-Y-butyrolactones via enantioselective tandem Michael-aldol reaction. Journal of Organic Chemistry, 78, 770-775. 

Dell C. P. Cycloaddition in Synthesis Contemporary Organic Synthesis 1997 4 87 Keywords natural products, metal catalyzed, asymmetric reactions, Ionic reactions, transannular reactions, tethered reactions, tandem reactions, benzo-qulnones, quinodimethanes, hefero-Dlels-Alder reactions... 

In recent years, the importance of aliphatic nitro compounds has greatly increased, due to the discovery of new selective transformations. These topics are discussed in the following chapters Stereoselective Henry reaction (chapter 3.3), Asymmetric Micheal additions (chapter 4.4), use of nitroalkenes as heterodienes in tandem [4+2]/[3+2] cycloadditions (chapter 8) and radical denitration (chapter 7.2). These reactions discovered in recent years constitute important tools in organic synthesis. They are discussed in more detail than the conventional reactions such as the Nef reaction, reduction to amines, synthesis of nitro sugars, alkylation and acylation (chapter 5). Concerning aromatic nitro chemistry, the preparation of substituted aromatic compounds via the SNAr reaction and nucleophilic aromatic substitution of hydrogen (VNS) are discussed (chapter 9). Preparation of heterocycles such as indoles, are covered (chapter 10). 

The chiral anisole derivative 37 has been used in the synthesis of several asymmetric functionalized cyclohexenes (Table 9) [22]. In a reaction sequence similar to that employed with racemic anisole complexes, 37 adds an electrophile and a nucleophile across C4 and C3, respectively, to form the cyclohexadiene complex 38. The vinyl ether group of 38 can then be reduced by the tandem addition of a proton and hydride to C2 and Cl, respectively, affording the alkene complex 39. Direct oxidation of 39 liberates cydohexenes 40 and 41, in which the initial asymmetric auxiliary is still intact. Alternatively, the auxiliary may be cleaved under acidic conditions to afford /y3 -allyl complexes, which can be regioselectively attacked by another nucleophile at Cl. Oxidative decomplexation liberates the cyclohexenes 42-44. HPLC analysis revealed high ee values for the organic products isolated both with and without the initial asymmetric group. 

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