Alkene reaction with alcohols

As catalysts Lewis acids such as AICI3, TiCU, SbFs, BF3, ZnCh or FeCl3 are used. Protic acids such as FI2SO4 or FIF are also used, especially for reaction with alkenes or alcohols. Recent developments include the use of acidic polymer resins, e.g. Nafion-Fl, as catalysts for Friedel-Crafts alkylations and the use of asymmetric catalysts. ... 

Osmium tetroxide, reaction with alkenes, 235-236 toxicity of, 235 Oxalic add, structure of, 753 Oxaloacetic acid, structure of, 753 Oxetane, reaction with Grignard reagents, 680 Oxidation, 233, 348 alcohols, 623-626 aldehydes, 700-701 aldoses, 992-994 alkenes, 233-236 biological, 625-626 phenols, 631 sulfides, 670 thiols, 668... 

Ene and Carbonyl-Ene Reactions. Certain double bonds undergo electrophilic addition reactions with alkenes in which an allylic hydrogen is transferred to the reactant. This process is called the ene reaction and the electrophile is known as an enophile A When a carbonyl group serves as the enophile, the reaction is called a carbonyl-ene reaction and leads to [3,-y-unsalurated alcohols. The reaction is also called the Prins reaction. 

Primary nitro compounds are good precursors for preparing nitriles and nitrile oxides (Eq. 6.31). The conversion of nitro compounds into nitrile oxides affords an important tool for the synthesis of complex natural products. Nitrile oxides are reactive 1,3-dipoles that form isoxazolines or isoxazoles by the reaction with alkenes or alky nes, respectively. The products are also important precursors for various substrates such as P-amino alcohols, P-hydroxy ketones, P-hydroxy nitriles, and P-hydroxy acids (Scheme 6.3). Many good reviews concerning nitrile oxides in organic synthesis exist some of them are listed here.50-56 Applications of organic synthesis using nitrile oxides are discussed in Section 8.2.2. 

This chapter deals mainly with the 1,3-dipolar cycloaddition reactions of three 1,3-dipoles azomethine ylides, nitrile oxides, and nitrones. These three have been relatively well investigated, and examples of external reagent-mediated stereocontrolled cycloadditions of other 1,3-dipoles are quite limited. Both nitrile oxides and nitrones are 1,3-dipoles whose cycloaddition reactions with alkene dipolarophiles produce 2-isoxazolines and isoxazolidines, their dihydro derivatives. These two heterocycles have long been used as intermediates in a variety of synthetic applications because their rich functionality. When subjected to reductive cleavage of the N—O bonds of these heterocycles, for example, important building blocks such as p-hydroxy ketones (aldols), a,p-unsaturated ketones, y-amino alcohols, and so on are produced (7-12). Stereocontrolled and/or enantiocontrolled cycloadditions of nitrones are the most widely developed (6,13). Examples of enantioselective Lewis acid catalyzed 1,3-dipolar cycloadditions are summarized by J0rgensen in Chapter 12 of this book, and will not be discussed further here. 

In trimethylenemethane complexes, the metal stabilizes an unusual and highly reactive ligand which cannot be obtained in free form. Trimethylenemethanetricar-bonyliron (R=H) was the first complex of this kind described in 1966 by Emerson and coworkers (Figure 1.2) [38]. It can be obtained by reaction of bromomethallyl alcohol with Fe(CO)5. Trimethylenemethaneiron complexes have been applied for [3+2]-cycloaddition reactions with alkenes [39]. 

Hydroxy(tosyloxy)iodo]benzene and Its Analogues Reactionswith Alkenes and Allenes. Reactions with Alkynes and Alcohols. Reactions with Keto Compounds. Reactions with Nitrogen, Sulfur, and Other compounds. 

The complexes will effect oxyamination reaction with alkenes in a stereospecific reaction (Scheme 8).290 After reductive cleavage of the intermediate alkanolaminato complex (I) (see below) vicinal amino alcohols (II) are formed. The reaction is unusual in that the new C—N bond is always formed at the least substituted terminal alkenic carbon atom, and there is a clear preference for the imido complex to use its NR group for coordination to the osmium despite the steric restraints of R.299,300 However, the least sterically hindered part of the alkene moiety is attached to. the nitrogen atom.290,291,300 The yields of amino alcohols in the reaction can be improved by addition of tertiary alkyl bulkhead amines (see below). 

An important use of Cp2ZrHCl is in the so-called hydrozirconation reaction with alkenes and alkynes which generates a Zr-alkyl group which can then be converted to alcohols or other products.67 In the reactions of CO with Zr and Hf compounds the oxophilicity of these elements is important, because it leads to the formation of a variety of compounds that have M—O bonds. 

Ozone, while somewhat inconvenient to use, is way qiecific in its reactions with alkenes. It is widely employed for selective synthesis, for qualitative and quantitative analysis of unsaturated compounds, and for studying the position of double bonds in macromolecules. The nature of the products obtained from ozonolysis reactions is determitted by the way in which the reaction is carried out Different workup procedures (hydrolytic, reductive or oxidative) can be used to produce alcohols, aldehydes, ketones, carboxylic acids or esters. 

Porphyrin hgands also allow the preparation of Cr complexes. For example, reaction of [(TPP)CrCl] with iodosylbenzene provides [(TPP)Cr(0)Cl], a six-coordinate complex, which is stable in solution for several hours. Its reaction with alkenes involves oxygen atom transfer and yields alcohols and epoxides. Another Cr porphyrin complex is the nitride [(TPP)CrN]. A crystal-stmcture determination has confirmed the square pyramidal structure with a very short bond distance to the apical lutrido ligand (Cr N, 156.5 pm). 

Several heteroatom nucleophiles, for example, amines, alcohols, thiols, carboxylates, and dialkylphosphines, undergo Michael addition reactions with alkene- and alkyne-substituted carbene complexes. Reaction of alkyne-substituted chromium carbenes with urea affords products derived from Michael... 

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