Valuable organic intermediates

Only after the World War II was the economic value of the hydroformylation reaction fully recognized and explored. As illustrated in Scheme 6.14.2, hydroformylation converts the petrochemical basic chemicals, olefin, and syngas, in a two-step sequence into several very valuable organic intermediates. Thus, alcohols, aldol products, polyols, amines, and carboxylic acids can be produced at very attractive raw material costs using the corresponding aldehyde formed primarily by hydroformylation as common intermediate. 

Scheme 6.14.2 Valuable organic intermediates and products obtained from n-butyraldehyde, the major product of propylene hydroformylation.

H )-Euranones are useful building blocks in the synthesis of a variety of organic compounds. In addition, they often serve as valuable synthetic intermediates in the stereoselective construction of substituted y-butyrolactones via conjugated addition to the Q ,/3-unsaturated carbonyl moiety or catalytic hydrogenation of the double bond (88JOC1560). 

Recently, we have observed a process where the palladium apparently migrates from a vinylic to an aryl to an allylic position all in one reaction (Scheme 27).23 This provides a unique new way to produce 7r-allylpalladium intermediates, which have proven very valuable as intermediates in organic synthesis. 

Asymmetric synthesis of cyanohydrins is an important process in organic synthesis because cyanohydrins can be easily converted into a variety of valuable synthetic intermediates such as a-hydroxy acids, a-hydroxy ketones, and g-amino alcohols. 

As noted at the beginning of this chapter, radicals are a unique class of organic intermediates because they can be studied using magnetic resonance techniques such as electron paramagnetic resonance spectroscopy (EPR). The EPR technique has proven valuable for ascertaining the local structure about a radical in a supercritical fluid solvent. 

Thioxanthenes are not only valuable synthetic intermediates [1], they also find considerable interest in pharmaceutical research [2] and as dyes for numerous applications [3]. Only few methods are known for the stereoselective synthesis of S-heterocycles [4], Sequential transformations are a powerful strategy in organic synthesis frequently allowing the synthesis of complex molecules in a single synthetic operation [5]. It was anticipated that 4-silyloxy-l-benzothiopyrylium-salts 1 [6], which represent double-activated 4-thiochromanones, can be used for the stereoselective synthesis of aimulated thiochromanones 3 by reaction with 2-silyloxy-l,3-butadienes 2 [7]. 

Asymmetric synthesis by means of a cyandiydrin is an imprvtant process in organic synthesis, because the cyanohydrin can be easily converted into a variety of valuable synthetic intermediates, such as a-hy-droxy ketones, a-hydroxy acids, y-diketones, p-amino alcohols, 4-oxocarboxylic esters, 4 xonitriles, a-amino acids and acyl cyanides. More specifically, the (S)-cyanohydrin of m-phenoxybenzaldehyde is a building block for the synthesis of the insecticide deltamethrin, or (IR)-cis-pyrethroids. ... 

Chiral secondary alcohols are one of the most valuable key intermediates for the synthesis of pharmaceuticals and advanced materials. The well-organized molecular catalyst 43, consisting of BINAP-Ru" and the chiral diamine, effects highly enantioselective hydrogenation of simple, unfuctionalized ketones to give secondary alcohols with over 99% ee in 100% yield (Scheme 12) [43]. In the presence of base, an alkali, the reaction proceeds in 2-propanol at room temperature under... 

The ubiquitous role of amines in both nature and in a vast variety of biologically important synthetic molecules gives this functionality a place of special prominence and interest in organic chemistry. Therefore, much effort and attention has been exerted toward developing methods for the selective synthesis of primary, secondary, and tertiary amines.4 In particular, the selective synthesis of secondary amines and orthogonally protected primary amines is quite important as these are often featured as valuable synthetic intermediates.5... 

From a synthetic chemist s point of view, it is not sufficient to demonstrate that "frozen" anti-aromatic tautomer of 1,2-pyrazole can be a good diene for the Diels-Alder reaction. It is of equal importance to illustrate that we can prepare functionalized 1,2-diazolse, which can be used as starting materials for the preparation of many different classes of organic compounds. For instance, it is possible to synthesize vinyl chloride as a valuable organic synthetic intermediate by taking advantage of the chemical transformations outlined in Scheme 14. 

Alcohols are sometimes viewed as central intermediates in the synthesis of complex molecules, because they are available from other materials and they can be converted to other types of compounds. The ability to convert alcohols to sulfonates for use in nucleophilic substitutions opens up a wide range of possibilities for the synthesis of valuable organic compounds. WeTl return to the use of alcohols in synthesis in Chapters 14 and 15. 

Most organic liquids can act as a solvent in industrial processes. Solvents are an important component in the chemical industry processes and in the application industries that utilize solvents as ingredients in their products. Many of the organic solvents described in this book also serve as chemical intermediates in preparation of other valuable organic chemicals. The data on the solvents included in this book was extracted from product literature given to the author by the various solvent producers. This data reflects the most current physical properties as well as the current use opportunities for the solvents and the most recent environmental and safety data. Environmental concerns often mandate solvent substitution. 

In light of these advantages, PCET has significant potential to expand the scope of homolytic bond activation catalysis in organic synthesis, and enable the direct generation of valuable radical intermediates directly from their native functional group precursors [37]. In support of this hypothesis, the remaining sections of this... 

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