A With Olefins

Allylic ethers (165) were first observed as products about ten years ago while allylic ketoalcohols (164) had been isolated much earlier. Investigation of the reaction of biacetyl with a-trideuteriomethylstyrene showed that the simple radical coupling mechanism illustrated above is not correct124) since the deuterium scrambling expected from reaction of a symmetrical 2-phenylallyl radical was not observed in the 

four types of products (often involving stereoisomers) may be formed in dione-olefin reactions. The situation is further complicated by the fact that product compositions show solvent and temperature-dependence 125) (effects of other variables have not been investigated) so that results from different laboratories have sometimes been at variance. Prediction of results is hazardous. 

The most extensively studied diketone has been biacetyl,24 12g) a detailed mechanistic study of its reactions with a number of olefins has appeared 128). It was suggested that a triplet exciplex is the precursor for formation of 161. The occurrence of electron transfer, presumably subsequent to exciplex formation, has been demonstrated 157,l58) in the reaction of biacetyl with tetramethyl-l,3-dioxole (167). Esr-spectroscopy of irradiated mixtures indicated the presence of biacetyl radical anion and dioxole radical cation. This reaction, which produced a complex mixture of products, was suggested to involve the excited singlet state of biacetyl. 

Other diones whose reactions with olefins have been reported include 1-phenyl-propane-1,2-dione 129) (nearly exclusive oxetane formation), 2,2,5,5-tetramethyl-tetrahydrofuran-3,4-dione 130), l,l,4,4-tetramethyltetralin-2,3-dione 131), and others, as well as the series of tetramethylcycloalkanediones 8 131) mentioned earlier. A number of intramolecular additions to give oxetanes were mentioned in the previous section. 

Additions of diketones (biacetyl, benzil, phenylpropanedione, phenylglyoxal) to thioacetylenes also occur 132). As in additions of monoketones to acetylenes, the 

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A little olefine accompanies the alkyl fiuoride produced and is readily removed by treatment with KBr—Brj solution. 

A fundamental difference exists between conventional acid-catalyzed and superacidic hydrocarbon chemistry. In the former, trivalent car-benium ions are always in equilibrium with olefins, which play the key role, whereas in the latter, hydrocarbon transformation can take place without the involvement of olefins through the intermediacy of five-coordinate carbocations. 

Cis-olefins or cis./rjns-dienes can be obtained from alkynes in similar reaction sequences. The alkyne is first hydroborated and then treated with alkaline iodine. If the other substituents on boron are alkyl groups, a cis-olefin is formed (G. Zweifel, 1967). If they are cir-alkenyls, a cis, trans-diene results. The reactions are thought to be iodine-assisted migrations of the cis-alkenyl group followed by (rans-deiodoboronation (G. Zweifel, 1968). Trans, trans-dienes are made from haloalkynes and alkynes. These compounds are added one after the other to thexylborane. The alkenyl(l-haloalkenyl)thexylboranes are converted with sodium methoxide into trans, trans-dienes (E. Negishi, 1973). The thexyl group does not migrate. 

Alkenes in (alkene)dicarbonyl(T -cyclopentadienyl)iron(l+) cations react with carbon nucleophiles to form new C —C bonds (M. Rosenblum, 1974 A.J. Pearson, 1987). Tricarbon-yi(ri -cycIohexadienyI)iron(l-h) cations, prepared from the T] -l,3-cyclohexadiene complexes by hydride abstraction with tritylium cations, react similarly to give 5-substituted 1,3-cyclo-hexadienes, and neutral tricarbonyl(n -l,3-cyciohexadiene)iron complexes can be coupled with olefins by hydrogen transfer at > 140°C. These reactions proceed regio- and stereospecifically in the successive cyanide addition and spirocyclization at an optically pure N-allyl-N-phenyl-1,3-cyclohexadiene-l-carboxamide iron complex (A.J. Pearson, 1989). 

Chloroacetate esters are usually made by removing water from a mixture of chloroacetic acid and the corresponding alcohol. Reaction of alcohol with chloroacetyl chloride is an anhydrous process which Hberates HCl. Chloroacetic acid will react with olefins in the presence of a catalyst to yield chloroacetate esters. Dichloroacetic and trichloroacetic acid esters are also known. These esters are usehil in synthesis. They are more reactive than the parent acids. Ethyl chloroacetate can be converted to sodium fluoroacetate by reaction with potassium fluoride (see Fluorine compounds, organic). Both methyl and ethyl chloroacetate are used as agricultural and pharmaceutical intermediates, specialty solvents, flavors, and fragrances. Methyl chloroacetate and P ionone undergo a Dar2ens reaction to form an intermediate in the synthesis of Vitamin A. Reaction of methyl chloroacetate with ammonia produces chloroacetamide [79-07-2] C2H ClNO (53). 

The use of silver fluoroborate as a catalyst or reagent often depends on the precipitation of a silver haUde. Thus the silver ion abstracts a CU from a rhodium chloride complex, ((CgH )2As)2(CO)RhCl, yielding the cationic rhodium fluoroborate [30935-54-7] hydrogenation catalyst (99). The complexing tendency of olefins for AgBF has led to the development of chemisorption methods for ethylene separation (100,101). Copper(I) fluoroborate [14708-11-3] also forms complexes with olefins hydrocarbon separations are effected by similar means (102). 

An important synthetic process for forming a new carbon—carbon bond is the acid-catalyzed condensation of formaldehyde with olefins (Prins reaction) ... 

In acetic acid solvent, ethylene gives 1,3-propanediol acetates (46) and propylene gives 1,3-butanediol acetates (47). A similar reaction readily occurs with olefinic alcohols and ethers, diolefins, and mercaptans (48). 

As the temperature approaches the NTC zone, the reversibility of reaction 2 comes into play and the steady-state concentration of alkyl radicals rises. There is a competing irreversible reaction of oxygen with radicals containing an alpha hydrogen which produces a conjugate olefin (eq. 23). 

Hydrogen atoms ate thought to play a principal role in the mechanistic steps of many reactions, including hydrocarbon thermolysis (119). Some reactions of atomic hydrogen with olefins and paraffins ate the following (120—122) ... 

An alternative approach involves the reaction of an alkyl carbamate with a tertiary olefin (89,90). The resultant carbamates are thermally cracked at temperatures of 150—350°C to yield the isocyanate. The isocyanate is generally purified via distillation. 

Chlorine heptoxide is more stable than either chlorine monoxide or chlorine dioxide however, the CX C) detonates when heated or subjected to shock. It melts at —91.5°C, bods at 80°C, has a molecular weight of 182.914, a heat of vapori2ation of 34.7 kj/mol (8.29 kcal/mol), and, at 0°C, a vapor pressure of 3.2 kPa (23.7 mm Hg) and a density of 1.86 g/mL (14,15). The infrared spectmm is consistent with the stmcture O CIOCIO (16). Cl O decomposes to chlorine and oxygen at low (0.2—10.7 kPa (1.5—80 mm Hg)) pressures and in a temperature range of 100—120°C (17). It is soluble in ben2ene, slowly attacking the solvent with water to form perchloric acid it also reacts with iodine to form iodine pentoxide and explodes on contact with a flame or by percussion. Reaction with olefins yields the impact-sensitive alkyl perchlorates (18). 

In the presence of a large excess of PH, primary phosphines, RPH2, are formed predominantiy. Secondary phosphines, R2PH, must be either isolated from mixtures with primary and tertiary products or made in special multistep procedures. Certain secondary phosphines can be produced if steric factors preclude conversion to a tertiary product. Both primary and secondary phosphines can be substituted with olefins. After the proper selection of substituents, mixed phosphines of the type RRTH or RR R T can be made. 

Polynuclear Aromatics. The alkylation of polynuclear aromatics with olefins and olefin-producing reagents is effected by acid catalysts. The alkylated products are more compHcated than are those produced by the alkylation of benzene because polynuclear aromatics have more than one position for substitution. For instance, the alkylation of naphthalene [91-20-3] with methanol over mordenite and Y-type zeoHtes at 400—450°C produces 1-methylnaphthalene [90-12-0] and 2-methylnaphthalene at a 2-/1- ratio of about 1.8. The selectivity to 2-methylnaphthalene [91-57-6] is increased by applying a ZSM-5 catalyst to give a 2-/1- ratio of about 8 (102). 

All lation of Aromatic Amines and Pyridines. Commercially important aromatic amines are aniline [62-53-3] toluidine [26915-12-8], phenylenediamines [25265-76-3], and toluenediamines [25376-45-8] (see Amines, aromatic). The ortho alkylation of these aromatic amines with olefins, alcohols, and dienes to produce more valuable derivatives can be achieved with soHd acid catalysts. For instance, 5-/ f2 butyl-2,4-toluenediamine (C H gN2), which is used for performance polymer appHcations, is produced at 85% selectivity and 84% 2,4-toluenediamine [95-80-7] (2,4-4L)A)... 

Ritter Reaction (Method 4). A small but important class of amines are manufactured by the Ritter reaction. These are the amines in which the nitrogen atom is adjacent to a tertiary alkyl group. In the Ritter reaction a substituted olefin such as isobutylene reacts with hydrogen cyanide under acidic conditions (12). The resulting formamide is then hydroly2ed to the parent primary amine. Typically sulfuric acid is used in this transformation of an olefin to an amine. Stoichiometric quantities of sulfate salts are produced along with the desired amine. 

G-All lation. Siace para-alkylated derivatives of DPA are widely used ia large volumes as antioxidants (qv), the most important reaction of DPA is the acid catalyzed reaction with olefins (2,3). Alkylation is carried out by adding the olefin to a mixture of DPA and an acid catalyst, such as AIQ. ... 

Olefin Complexes. Silver ion forms complexes with olefins and many aromatic compounds. As a general rule, the stabihty of olefin complexes decreases as alkyl groups are substituted for the hydrogen bonded to the ethylene carbon atoms (19). 

Hydrogen sulfide reacts with olefins under various conditions forming mercaptans and sulfides (108,109). With ethylene it can react to ultimately give diethyl sulfide (110). With unsymmetrical olefins, the direction of addition can be controlled by the choice of either a free-radical initiator, including ultraviolet light, or an acidic catalyst (110) ... 

With a few olefins, the addition can yield sulfenyl chlorides, eg, 2-dichloroethane sulfenyl chloride [2441 -27-2] ... 

Miscellaneous Copolymers. VP has been employed as a termonomer with various acryUc monomer—monomer combinations, especially to afford resins usehil as hair fixatives. Because of major differences in reactivity, VP can be copolymerized with alpha-olefins, but the products are actually PVP grafted with olefin or olefin oligomers (151,152). Likewise styrene can be polymerized in the presence of PVP and the resulting dispersion is unusually stable, suggesting that this added resistance to separation is caused by some grafting of styrene onto PVP (153). The Hterature contains innumerable references to other copolymers but at present (ca 1997), those reviewed in this article are the only ones known to have commercial significance. 

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