Olefin and Acetylene Compounds

Since 1971 several studies involving olefins or acetylenes as leaving groups have appeared. Consequently this section is included in this chapter for the first time. The displacement of cis-cyclo-octene from [(A -C5Hs)Mn(CO)(CS)-(CgHu)] by PPhs proceeds at a rate that is independent of [PPhj], which together with a value of A5 of 85.0 11.6 J mol indicates a likely S l mechanism. Loss of CH2=CHX from five-co-ordinate [Fe(CO)4-(CHa=CHX)] (X = OEt, Bu, Ph, COgMe, or CN) on reaction with CO also 

The observed rate of C2H4 evolution is controlled by the relative values of ki and kg, which are in turn governed by whether L (see Table 6) stabilizes or destabilizes the intermediate [(/r -C5H5)Rh(C2H4)L]. L may therefore influence the observed rate even though the reaction is dissociative. Values obtained are summarized in Table 6.  

66 [(/t5-C5H5)Rh(C2H4)2] Diethyl fumarate Diphenyl ether 2.93 391 

66 rate constant may apply to dissociation of the first and/or second ethylene ligand. The limits are ki - 2ki. 

In contrast to the predominantly dissociative mechanisms described above, the reaction 

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Some preparations of olefinic and acetylenic compounds from olefinic and acetylenic starting materials can, in principle, be classified in either the monofunctional or difunctional sections for example, RCH=CHBr - RCH=CHCOOH, carboxylic acids from halides (Section 25, monofunctional compounds) or carboxylic acid-olefin (Section 322, difunctional compounds). In such cases both sections should be consulted. 

Palladium chloride and metallic palladium are useful for carbonylating olefinic and acetylenic compounds. Further, palladium is active for decarbonylation of aldehydes and acyl halides. Homogeneous decarbonylation of aldehydes and acyl halides and carbonylation of alkyl halides were carried out smoothly using rhodium complexes. An acyl-rhodium complex, thought to be an intermediate in decarbonylation, was isolated by the oxidative addition of acyl halide to chlorotris(triphenylphosphine)rhodium. The mechanisms of these carbonylation and decarbonylation reactions are discussed. 

Catalytic alkylation of alkylsilanes with olefinic and acetylenic compounds using solid catalysts was examined in a closed recirculation reactor at 373 - 473 K. Alkylation of diethylsilane(E2) with these compounds took place smoothly on silica-alumina (SA) and S03/Zr02 catalysts but not on alumina, which means protonic solid acid catalyzed the reaction. n-Alkylated products were the main products and the /so-alkylated ones were the minor products regardless the type of olefins. The product distribution indicates the reaction takes place via a nucleophilic attack of olefins on a Si cation. 

This paper deals with the feasibility study of the catalytic disproportionation of alkylsilanes and the catalytic alkylation of diethylsilane with olefinic and acetylenic compounds by using solid acid and base catalysts. 

Inverse electron demand cycloaddition of 1,2,4,5-tetrazine with alkenes and alkynes. Inverse electron demand Diels-Alder addition has also been employed for the synthesis of pyridazines and condensed pyridazines. The reaction of olefinic and acetylenic compounds with 3,6-disubstituted 1,2,4,5-tetrazines 142 to yield substituted pyridazines 144 by the intermediacy of 143 was first reported by Carboni and Lindsey (1959JA4342). Analogous reaction of 142 with a variety of aldehydes and ketones 145 in base at room temperature proceeded smoothly to yield the corresponding pyridazines 144. Compounds 146-148 are proposed nonisolable intermediates (1979JOC629 Scheme 26). 

Heats of cis —> traiis isomerizsation from heats of hydroge>mtion of non-cycUc olefinic and acetylenic compounds... 

Therefore 4d and 5d electron metals interact with ligands in a more effective manner and thus form more covalent compounds. Because of valence orbital energy and orbital sizes, compounds of these elements in their lower oxidation states, particularly organometallic ones, are more stable than analogous complexes of M electron metals. The increased stability of olefin and acetylene compounds with increasing atomic number in a given group may serve as an example. Olefin complexes of cobalt are few and very unstable, while rhodium and iridium olefin compounds are quite common and usually air-stable. 

Pd is an efficient catalyst for carbonylation of olefinic and acetylenic compounds and aryl halides to form various saturated and unsaturated carboxylic acids, their esters, and lactones. Also, aldehydes are obtained using Pd catalysts. For a long time, Pd has been known as an efficient catalyst for decarbonylation of aldehydes. Acyl halides are also de-carbonylated with Pd catalysts. Now it is well-established that Pd is the efficient catalyst for both carbonylation and decarbonylation as reversible processes. 

The substitution of CO in metal carbonyls by olefinic and acetylenic compounds is one of the chief methods for preparing tt complexes of transition metals. Unfortunately this procedure fails almost completely when applied to nickel carbonyl, and this may be one of the reasons why until recently no tt complexes of nickel with olefinic or acetylenic ligands were known. The reasons for this behavior of nickel carbonyl will become clearer, if both its electronic structure and the mechanism of the ligand exchange reactions are considered. 

The reaction of carbon dioxide with multiple bonded carbon derivatives proceeds in the presence of nickel (o) catalysts to give five-membered ring metallacycles, which on hydrolysis produce carboxylic acid derivatives. This derivatization of olefins and acetylene compounds is of considerable interest in synthetic organic chemistry. 

The high acidity of superacids makes them extremely effective pro-tonating agents and catalysts. They also can activate a wide variety of extremely weakly basic compounds (nucleophiles) that previously could not be considered reactive in any practical way. Superacids such as fluoroantimonic or magic acid are capable of protonating not only TT-donor systems (aromatics, olefins, and acetylenes) but also what are called (T-donors, such as saturated hydrocarbons, including methane (CH4), the simplest parent saturated hydrocarbon. 

Olefin and acetylene complexes of Au(I) can be prepared by direct iateraction of the unsaturated compounds with a Au(I) hahde (190,191). The resulting products, however, are not very stable and decompose at low temperatures. Reaction with Au(III) hahdes leads to halogenation of the unsaturated compound and formation of Au(I) complexes or polynuclear complexes with gold ia mixed oxidatioa states. 

Methyl ketones are important intermediates for the synthesis of methyl alkyl carbinols, annulation reagents, and cyclic compounds. A common synthetic method for the preparation of methyl ketones is the alkylation of acetone derivatives, but the method suffers limitations such as low yields and lack of regioselectivity. Preparation of methyl ketones from olefins and acetylenes using mercury compounds is a better method. For example, hydration of terminal acetylenes using HgSO gives methyl ketones cleanly. Oxymercuration of 1-olefins and subsequent oxidation with chromic oxide is... 

Selenium diimides react in a manner similar to SeOa with unsaturated organic compounds. The first report of BuN=Sc=N Bu described its use as an in situ reagent for allylic amination of olefins and acetylenes. Improved procedures for this process (Eq. 10.5) and for the diamination of 1,3-dienes (Eq. 10.6) have been developed using the reagents RN=Se=NR [R = para-toluenesulfonyl (Ts), ort/io-nitrobenzenesulfonyl (Ns)]. ... 

Due to their weak P-H bonds (-370 kj mol"0 [2] and the high rate constants for the transfer of the P-H hydrogen [3] (/c=1.5 10 L rnoL s" for Ph2PH and k=5,0 10 L mol s for (c-hexyl)2PH), diaryl and dialkyl phosphines present a high interest as H-donors. Since the corresponding phosphinyl radicals are good chain carriers [4,5], diaryl and dialkyl phosphines can be added to olefinic or acetylenic compounds through radical chain reactions. Simpkins et al. [6] used... 

Tetrazolium ylides are quite reactive and are easily alkylated.168 The mesoionic tetrazolium thiolate 117 readily adds bromine to yield 174 which can then react with a number of active methylene compounds to give mesoionic compounds, e.g., 175.293,294 They also undergo 1,3-dipolar cycloaddition with olefins and acetylenes to yield bicyclic tetrazolo-thiazolines... 

The C-H bond activation followed by addition to a double bond leads to the formation of alkylated compounds (Equation (1)). This reaction involves aromatic, aliphatic, olefinic, and acetylenic C-H bonds. 

When olefins are treated with N204 in an ether, ester, or alkane as solvent, vtc-dinitro compounds and 3-nitro alkyl nitrites are produced.803 The reaction can be successfully performed with all kinds of olefins and acetylenes. Generally, both products are produced. The dinitro compound is usually stable, but the ester is quite reactive. Upon addition of water or alcohol it is hydrolyzed to a 3-nitro alcohol. If oxygen is added, it is oxidized to a 3-nitro alkyl nitrate or an a-nitro aldehyde or ketone. 

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