Alkenes in Organic Synthesis

Sample Problem 10.7 Draw the product of each reaction. 

Problem 10.32 Draw the products of each reaction using the two-part strategy from Sample Problem 10.7. 

Alkenes are a central functional group in oiganic chemistry. Alkenes are easily prepared by elimination reactions such as dehydrohalogenation and dehydration. Because their n bond is easily broken, they undergo many addition reactions to prepare a variety of useful compounds. 

Suppose, for example, that we must synthesize 1,2-dibromocyclohexane from cyclohexanol, a cheap and readily available starting material. Because there is no way to accomplish this transformation in one step, this synthesis must have at least two steps. 

In Chapter 11 we will learn about retrosynthetic analysis in more detail. 

In each problem, identify the functional group to determine the general reaction type—substitution, elimination, or addition. Then, determine if the reagent is an electrophile, nucleophile, acid, base, and so forth. 

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Ruthenium-catalyzed Addition of Sulfonyl Chlorides to Alkenes in Organic Synthesis 337... 

Heteroatoms can be incorporated into the n framework of either the alkene partner or the diene partner of Diels-Alder reactions. This section will focus on two structural types that function as dienophiles ketones or aldehydes, and imines (162), as well as three types that function as dienes conjugated carbonyls (163), 1-azadienes (164), and 2-azadienes (165). The use of heteroatom dienes and alkenes in organic synthesis was thoroughly reviewed in the monograph of Boger and Weinreb and that of Fringuelli and Taticchi.i b... 

This chapter discusses some general aspects of the hydroformylation of alkenes in organic synthesis. It focuses mainly on regio- and stereoselective processes, and analyzes the influence of the substrate and the catalysts. Practical methods which provide high yields and selectivities, and short-cuts compared to classical organic routes will be described. Particular attention will be paid to recent advances that have helped to enlarge the synthetic application of this reaction. Section 6.7 deals with the hydroformylation of alkynes, and such key aspects as hydroformylation in water-gas shift conditions and silylformylation, particularly efficient catalytic systems and the application ofhydroformylation in organic synthesis. 

H. Alper, Pure Appl. Chem., 1988, 60, 35-38. Metal Catalyzed Carbonylation and Oxidation-Reduction Reactions. W. Oppolzer, Pure Appl. Chem., 1988, 60, 39-48. Metal-Directed Stereoselective Eunctionalizations of Alkenes in Organic Synthesis. 

The overall result of the sequence hydroboration -I- oxidation is a regioselective and-Markownikoff-addition of water to an alkene. This reaction is an important method in organic synthesis, since it can be made stereoselective and even enantioselective. 

The reaction of ozone with an aromatic compound is considerably slower than the reaction with an alkene. Complete ozonolysis of one mole of benzene with workup under non-oxidative conditions will yield three moles of glyoxal. The selective ozonolysis of particular bonds in appropriate aromatic compounds is used in organic synthesis, for example in the synthesis of a substituted biphenyl 8 from phenanthrene 7 ... 

Enamines 1 are useful intermediates in organic synthesis. Their use for the synthesis of a-substituted aldehydes or ketones 3 by reaction with an electrophilic reactant—e.g. an alkyl halide 2, an acyl halide or an acceptor-substituted alkene—is named after Gilbert Stork. 

The introducdon of heterodienes has extended the synthedc versatility of cyclokldmon teac-dons in organic synthesis. " Denmark and coworkers have developed the use of rutroalkenes as dienes in [4+2 cycloaddidon. Nitroalkenes react v/ith simple alkenes in the presence of SnCi, as a promoter. For example, the reacdon of tutrocyclohexene v/ith cyclopentene gives three products. The major product is ruiri-isoraer, which arises from an fixn approach of cyclopentene toward tutrocyclohexene fsee Eq. 8.94. ... 

Alcohols undergo many reactions and can be converted into many other functional groups. They can be dehydrated to give alkenes by treatment with POCI3 and can be transformed into alkyl halides by treatment with PBr3 or SOCU- Furthermore, alcohols are weakly acidic (p/C, — 16-18) and react with strong bases and with alkali metals to form alkoxide anions, which are used frequently in organic synthesis. 

Intermediates 18 and 19 are comparable in complexity and complementary in reactivity. Treatment of a solution of phosphonium iodide 19 in DMSO at 25 °C with several equivalents of sodium hydride produces a deep red phosphorous ylide which couples smoothly with aldehyde 18 to give cis alkene 17 accompanied by 20 % of the undesired trans olefin (see Scheme 6a). This reaction is an example of the familiar Wittig reaction,17 a most powerful carbon-carbon bond forming process in organic synthesis. 

The intramolecular cycloaddition of a nitrile oxide (a 1,3-dipole) to an alkene is ideally suited for the regio- and stereocontrolled synthesis of fused polycyclic isoxazolines.16 The simultaneous creation of two new rings and the synthetic versatility of the isoxa-zoline substructure contribute significantly to the popularity of this cycloaddition process in organic synthesis. In spite of its high degree of functionalization, aldoxime 32 was regarded as a viable substrate for an intramolecular 1,3-dipolar cycloaddition reaction. Indeed, treatment of 32 (see Scheme 17) with sodium hypochlorite... 

Fiirstner A (1998) Alkene metathesis in organic synthesis (Topics in organometallic chemistry I). Springer, Berlin Heidelberg New York... 

Addition of phosphonyl radicals onto alkenes or alkynes has been known since the sixties [14]. Nevertheless, because of the interest in organic synthesis and in the initiation of free radical polymerizations [15], the modes of generation of phosphonyl radicals [16] and their addition rate constants onto alkenes [9,12,17] has continued to be intensively studied over the last decade. Narasaka et al. [18] and Romakhin et al. [19] showed that phosphonyl radicals, generated either in the presence of manganese salts or anodically, add to alkenes with good yields. 

Aziridines are versatile intermediates in organic synthesis and commonly found in bioactive molecules. The transition metal-catalyzed nitrene transfer to alkenes is an attractive method for the synthesis of aziridines [7]. In 1984, Mansuy and coworkers reported the first example of an iron-catalyzed alkene aziridination in which iron porphyrin [Fe(TTP)Cl] was used as catalyst and PhINTs was used as nitrene source [30]. Subsequently, the same authors demonstrated that [Fe(TDCPP) (CIO4)] is a more efficient and selective catalyst than [Fe(TTP)Cl] (Scheme 20). 

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