Organic synthesis directing groups

It is interesting to note recent mechanistic aspects of the catalytic Mukaiyama aldol reaction, although there might be few direct advantages in organic synthesis. Two groups attempted to determine the nature of the Lewis acidic species during the course of the reaction effected by catalytic use of some metal triflates (Sch. 5). Bos-nich et al. came to two conclusions [27] ... 

Direct substitution of the carbonyls themselves is of course possible. Besides Group 15 donor ligands, unsaturated hydrocarbons give especially interesting products. The iron carbonyl acetylenes provided early examples of the use of carbonyls in organic synthesis. From them a wide variety... 

In recent years, the emphasis of research has been directed more and more toward utilizing nitro compounds as reactive intermediates in organic synthesis. The activating effect of the nitro group is exploited in carrying out many organic reactions, and its facile transformation into various functional groups has broadened the importance of nitro compounds in the synthesis of complex molecules. 

It should be added that many other groups have contributed to the predevelopments of these inventions and also to later developments. All four reactions find wide application in organic synthesis. The Sharpless epoxidation of allylic alcohols finds industrial application in Arco s synthesis of glycidol, the epoxidation product of allyl alcohol, and Upjohn s synthesis of disparlure (Figure 14.4), a sex pheromone for the gypsy moth. The synthesis of disparlure starts with a Ci3 allylic alcohol in which, after asymmetric epoxidation, the alcohol is replaced by the other carbon chain. Perhaps today the Jacobsen method can be used directly on a suitable Ci9 alkene, although the steric differences between both ends of the molecules are extremely small ... 

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