Novel conjugate reactions discussion

Novel asymmetric conjugate-type reactions have been accomplished with Cinchona alkaloid-derived chiral thioureas, including less traditional reactions such as asymmetric decarboxylation [71]. In the following discussion, asymmetric reactions involving nitro-olefms, aldehydes and enones, and imines will be highlighted (Fig. 5). 

Most of the fundamental reactions of disilenes have been studied and discussed extensively in previous review articles. During the last decade, many new types of reactions have been found for novel types of disilenes such as cyclic and bicyclic disilenes, and conjugated tetrasiladienes. Mechanistic studies have recently been performed on several fundamental reactions of disilenes both theoretically and experimentally, and have greatly deepened our understanding of their reaction pathways, their potential energy surfaces, the factors determining the rates and stereochemistry, and so on. 

Pd-catalyzed conjugate substitution, as defined in Scheme 1 of Sect. III.2.15, is nothing more than Pd-catalyzed alkenylation with /3-halo- or /3-metallo-substituted a,/3-unsaturated carbonyl compounds and related derivatives. Since the reaction is closely related to the widely known conjugate addition and since it can serve as the component of a novel and alternative conjugate addition protocol, their special discussion is warranted. 

It has been generally accepted that polyacetylene has a planar structure, irrespective of cis and trans forms, due to ir-conjugation between the sp hybridized carbon atoms in the polymer chain [1,4]. If it were possible to modify such a planar structure of pofyacetylene into a hehcal one [13], one might expect novel magnetic and optical properties [14]. Here, we report polymerization of acetylene in asymmetric reaction field constructed with chiral nematic LCs, and show that pofyacetylene films formed by helical chains and fibrils can be synthesized [15]. Polymerization mechanism giving hehcal structure from primary to higher order and hierarchical spiral morphology is discussed. 

The fact that the three conjugated unsaturations in the tung oil chains behave like a diene moiety in the Diels-Alder reaction has been exploited in original ways to prepare novel polymers. This topic is discussed in Chapter 7, which is devoted to application of that click chemistry mechanism. 

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