Reactions Involving Other Functional Groups

The most interesting of these reactions are those CH = N-CHR-COOH (1.44a) in which a-amino and a-carboxyl groups are 

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With these remarks on heterogeneous processes we conclude our discussion of hydrolytic reactions and other reactions involving nucleophilic species. We should point out that we have taken a close look at only a few representative structural moieties that may undergo these types of reactions in the environment. Nevertheless, the general knowledge that we have acquired in this chapter should put us in a much better position to evaluate the importance of such reactions for other functional groups that form part of environmental organic chemicals. 

Most reactions of diazomethane with these heterocyclic systems involve attack at other functional groups (for a review see ref. 1), such as in the 0- and iV -methylation of the hydroxy-pyridines and -quino-... 

Similar to the intramolecular insertion into an unactivated C—H bond, the intermolecular version of this reaction meets with greatly improved yields when rhodium carbenes are involved. For the insertion of an alkoxycarbonylcarbene fragment into C—H bonds of acyclic alkanes and cycloalkanes, rhodium(II) perfluorocarb-oxylates 286), rhodium(II) pivalate or some other carboxylates 287,288 and rhodium-(III) porphyrins 287 > proved to be well suited (Tables 19 and 20). In the era of copper catalysts, this reaction type ranked as a quite uncommon process 14), mainly because the yields were low, even in the absence of other functional groups in the substrate which would be more susceptible to carbenoid attack. For example, CuS04(CuCl)-catalyzed decomposition of ethyl diazoacetate in a large excess of cyclohexane was reported to give 24% (15%) of C/H insertion, but 40% (61 %) of the two carbene dimers 289). 

Only transformations in the longest linear sequence (LLS) are considered. The term skeleton constructions refers to C-C and C-O bond formations (notwithstanding redox reactions) that directly introduce native structural features of the bryostatins without further modification. The term other functional group manipulations refers to steps that indirectly introduce native structural elements, the interconversion of functional groups (e.g., the introduction and removal of auxiliaries) and miscellaneous transformations that do not involve skeleton construction... 

The chemistry of nitro compounds forms the basis of a number of well-known processes, such as the Henry or the Nef reactions . Transformations such as the latter permit the interconversion between nitro and other functional groups and are therefore of prime importance. The most commonly employed methods for the reduction of primary nitroalkanes to oximes involve the use of BusSnH, Se/NaBH4, CS2 or SnCla (often in combination with thiophenol) . 

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