Substrate versatility, major

It is the purpose of the remainder of this review to survey the major conjugation reactions, in terms of their substrate versatility, enzymic mechanism and distribution amongst manmallan... 

The synthesis of lactams has attracted considerable attention in recent years. This is presumably because they represent versatile synthetic intermediates that are present h many biologically important molecules. Despite the wide range of methodologies that have been examined for the synthesis of lactams, the Beckmann and Schmidt rearrangements still remain by far the most convenient and general methods. The strongly acidic conditions required for the Schmidt rearrangement often lead to undesired byproducts. This is a major limitation particularly with acid-labile substrates. 

The carbonylation of allylic compounds by transition metal complexes is a versatile method for synthesizing unsaturated carboxylic acid derivatives (Eq. 11.22) [64]. Usually, palladium complexes are used for the carbonylation of allylic compounds [65], whereas ruthenium complexes show characteristic catalytic activity in allylic carbonylation reactions. Cinnamyl methyl carbonate reacts with CO in the presence of a Ru3(CO)i2/l,10-phenanthroline catalyst in dimethylformamide (DMF) to give methyl 4-phenyl-3-butenoate in excellent yield (Eq. 11.23) [66]. The regioselectivity is the same as in the palladium complex-catalyzed reaction. However, when ( )-2-butenyl methyl carbonate is used as a substrate, methyl ( )-2-methyl-2-butenoate is the major product, with the more sterically hindered carbon atom of the allylic group being carbo-nylated (Eq. 11.24). This regioselectivity is characteristic of the ruthenium catalyst [66]. 

The major commercial anion exchangers for ion chromatography are based on two substrate types macroporous and microporous (or gel-type) materials. Microporous substrates are used primarily as supports for pellicular, latex-coated beads. This type of column is efficient and versatile. Many different column types with different selec-... 

The asymmetric catalytic reduction of ketones (R2C=0) and imines (R2C=NR) with certain organohydrosilanes and transition-metal catalysts is named hydrosilylation and has been recognized as a versatile method providing optically active secondary alcohols and primary or secondary amines (Scheme 1) [1]. In this decade, high enantioselectivity over 90% has been realized by several catalytic systems [2,3]. Therefore the hydrosilylation can achieve a sufficient level to be a preparative method for the asymmetric reduction of double bond substrates. In addition, the manipulative feasibility of the catalytic hydrosilylation has played a major role as a probe reaction of asymmetric catalysis, so that the potential of newly designed chiral ligands and catalysts can be continuously scrutinized. 

---