Functional Group Oxidation Reactions

Palladium(0)-catalyzed coupling reactions - i. e. the Heck and Sonogashira reactions, the carbonylative coupling reactions, the Suzuki and Stille cross-coupling reactions, and allylic substitutions (Fig. 11.1) - have enabled the formation of many kinds of carbon-carbon attachments that were previously very difficult to make. These reactions are usually robust and occur in the presence of a wide variety of functional groups. The reactions are, furthermore, autocatalytic (i.e. the substrate regenerates the required oxidation state of the palladium) and a vast number of different ligands can be used to fine-tune the reactivity and selectivity of the reactions. 

Krikorian, S.E. 1988. Methodology for quantifying functional group oxidation state levels and for analyzing organic reactions for oxidation-reduction behavior. Am. J. Pharm. Educ. 52, 177-180. 

Oxidation of alcohol, carbonyl and acid functions, hydroxylation of aliphatic carbon atoms, hydroxylation of alicyclic carbon atoms, oxidation of aromatic carbon atoms, oxidation of carbon-carbon double bonds, oxidation of nitrogen-containing functional groups, oxidation of silicon, phosphorus, arsenic and sulfur, oxidative N-dealkylation, oxidative O- and S-dealkylation, oxidative deamination, other oxidative reactions... 

In fine-chemicals production three-phase reaction systems are common for the hydrogenation and hydrogenolysis of different organic functional groups. Other reactions, such as heterogeneously catalyzed catalytic oxidations, hydrodesulfurizations, and reductive aminations are encountered less frequently. 

Given this structural diversity, the continued development of new reactions is also crucial. Even in cases where a modification strategy is already in place for a particular functional group, alternative reactions can allow expansions in substrate scope, alterations in modification selectivity, synthetic convenience, and perhaps even greater biocompatibility. Just as a well-trained synthetic chemist must know a dozen methods for the oxidation of an alcohol to an aldehyde, protein bioconjugation will be approached with much more success if many techniques are available to address the situation at hand. 

Because monosaccharides contain alcohol functional groups and aldehyde (or ketone) functional groups, the reactions of monosaccharides are an extension of what you have already learned about the reactions of alcohols, aldehydes, and ketones. For example, an aldehyde group in a monosaccharide can be oxidized or reduced and can react with nucleophiles to formimines, hemiacetals, and acetals. When you read the sections that deal with the reactions of monosaccharides, you will find cross-references to the sections in which the same reactivity for simple organic compounds is discussed. As you study, refer back to these sections they will make learning about carbohydrates a lot easier and will give you a good review of some chemistry that you have already learned about. 

The introduction to organic reactions will be continued in the functional group exchange reactions presented in Chapter 2. That chapter will review the reactions introduced in a typical first organic chemistry course. Some of the concepts will be expanded and updated to include more synthetically useful reactions. Oxidation and reduction will be presented in separate chapters to focus attention on the vast number of reactions that fall under these categories. 

Important work by Chen et al. [123b] has shown how borylation of alkanes can be achieved both photochemically and thermally from diboron reagents to give alkylboranes (Eq. 2.43). The best catalysts, [CpRh(ethylene)2] and [Cp Rh(r/ -CeMce)], are active at 150°C. The B-B bond oxidatively adds to the metal probably followed by CH oxidative addition. Reductive eMmination gives rise to a new B-C bond being formed. Functionalization occurs at the terminal position of a linear alkane as in the alkane chemistry described above. Since C-B bonds are in principle precursors to a wide variety of functional groups, this reaction has great promise for future development. 

Side chains of alkylbenzenes are oxidized to benzoic acid derivatives by treatment with hot potassium permanganate or hot chromic acid. Because this oxidation requires severe reaction conditions, it is useful only for making benzoic acid derivatives with no oxidizable functional groups. Oxidation-... 

Review the oxidation reactions of glycolysis, /3-oxidation, and the citric acid cycle, and compare the types of functional groups oxidized by NAD with those oxidized by FAD. 

Oxidation of alcohols converts an alcohol to a ketone or an aldehyde. It is also possible to oxidize a primary alcohol to a carboxylic acid. The functional group exchange reactions therefore show a ketone or aldehyde with an alcohol precursor and a carboxylic acid with a primary alcohol precursor. 

Functional group analysis Reaction of a specific group with a known reagent. Acids, bases, and oxidizing and reducing agents are common. Example titration of carboxyl groups. (b.c)... 

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