Transition metal-catalyzed synthetic methodolog

In addition to the applications reported in detail above, a number of other transition metal-catalyzed reactions in ionic liquids have been carried out with some success in recent years, illustrating the broad versatility of the methodology. Butadiene telomerization [34], olefin metathesis [110], carbonylation [111], allylic alkylation [112] and substitution [113], and Trost-Tsuji-coupling [114] are other examples of high value for synthetic chemists. 

The last few decades have witnessed some exciting developments of synthetic methodologies in organic chemistry. Chiefly among these developments are ringclosing metathesis (RCM) and transition metal-catalyzed C-H activation, which have emerged as novel and useful tools. 

This chapter mainly treats transition metal-catalyzed direct functionalization of carbon-hydrogen bonds in organic compounds. This methodology is emphasized by focusing on important functionalizations for synthetic use. The contents reviewed here are as follows (i) alkylation of C-H bonds, (ii) alkenylation of C-H bonds, (iii) arylation of C-H bonds, (iv) carbonylation of C-H bonds, (v) hydroxylation and the related reactions, and (vi) other reactions and applications. 

The main topics of these symposia were collected in this book and the themes were regrouped under the umbrella of Glycomimetics Modem Synthetic Methodologies. The authors were asked to include key experimental details dealing with modem synthetic procedures, most of which describe the use of delicate transition metal catalyzed reactions. Thus this book will be a valuable tool for well-trained traditional glycochemists and particularly for newcomers in the field of glycomimetics. The subject index at the end of the book will help the readers retrieve die desired informations. 

Much effort has been devoted to studies of thiophene oligomers and polymers, in particular in connection with development of new organic materials for electronic applications. Many of the synthetic approaches towards oligothiophenes rely on well-established methodology, such as metalations, halogen-metal exchange reactions, and transition metal catalyzed couplings. 

On the other hand, carboryne, l,2-dehydro-t -carborane, is a three-dimensional relative of benzyne (Fig. 7.1) [6]. It can react with alkenes, dienes, and alkynes in [2-1-2], [4-1-2] cycloaddition and ene-reaction patterns [7], similar to those of benzyne [8], Although these reactions show the potential for the preparation of functionalized carboranes in a single operation, they are complex and do not proceed in a controlled manner. In view of the spectacular role of transition metals in synthetic chemistry, we envisage that the aforementioned reactions may work efficiently and in a controlled way with the help of transition metals. In this connection, we initiated a research program to develop transition-metal-mediated/catalyzed synthetic methodologies for the functionalization of carboranes. This chapter summarizes the recent progress in this research area. 

In the 1980s, the group of Trost [10,11] discovered and developed intramolecular palladium-catalyzed Alder-ene reactions. Changing the mechanism from the classical pericyclic process to a reaction that proceeds via transition organometal-lic intermediates has enriched the understanding and realization of the concept of atom-economic processes [ 12]. Therefore, the cycloisomerization of 1,/i-enynes has remained an intensively pursued field of synthetic methodologies ever since [13]. In addition, major advances in enantioselective transition-metal-catalyzed cycloisomerizations of enynes have also been explored [14]. 

Before this total synthesis project began, we had just completed a diversity-oriented synthesis project that made use of the allylboration reaction to access simple substituted a-methylene y-lactones, which were further functionalized using a variety of transition metal-catalyzed reactions. We were now interested in applying this allylboration methodology to pursue a target-oriented synthetic problem that would demonstrate its suitability toward a complex natural product. Chinensiolide B presented this sort of challenge. 

---