Olefins additions

Similar reactions can also be written for the alkoxysilanes but in commercial practice the chlorosilanes are favoured. These materials may be prepared by many routes, of which four appear to be of commercial value, the Grignard process, the direct process, the olefin addition method and the sodium condensation method. 

Additions of halogen fluorides to the more electrophilic perfluonnated olefins generally require different conditions Reactions of iodine fluoride, generated in situ from iodine and iodine pentafluoride [62 102 103, /05] or iodine, hydrogen fluoride, and parapeiiodic aud [104], with fluormated olefins (equations 8-10) are especially well studied because the perfluoroalkyl iodide products are useful precursors of surfactants and other fluorochemicals Somewhat higher temperatures are required compared with reactions with hydrocarbon olefins Additions of bromine fluoride, from bromine and bromine trifluonde, to perfluonnated olefins are also known [lOti]... 

With more electrophilic halogenated olefins, additions of tnfluoromethyl hypofluonte appear to go by radical processes [139] and give oligomeric products [140] or one-to-one adducts [141,142] (equation 4) depending on reaction conditions... 

Substituted TMMs also participate smoothly in imine cycloaddition to generate more structurally elaborate pyrrolidines. The regioselectivity of these reactions is similar to that of olefin addition, although subsequent isomerization of the initial adduct is often observed. For example, the cyano system produced the thermody-... 

A conventional FCC unit can be an olefin machine with proper operating conditions and hardware. Catalysts with a low unit cell size and a high silica/alumina ratio favor olefins. Additionally, the addition of ZSM-5, with its lower acid site density and very high framework silica-alumina ratio, converts gasoline into olefins. A high reactor temperature and elimination of the post-riser residence time will also produce more olefins. Mechanical modification of the FCC riser for millisecond cracking has shown potential for maximizing olefin yield. 

The principal organic reaction of ozone is its addition to the carbon-carbon double bond of an ethylenic compd. The resulting ozone-olefin addition compd is known as an ozonide. Decompn of the ozonide gives a mixt of oxygenated products containing carbonyl compds and acids. 

The primary ozone-olefin addition product splits into a molozonide zwitterion (3). The zwitterion (3) then stabilizes by splitting into a carbonyl compd (4) and another zwitterion (5). 

No. Carboxylic acid Olefin Additive monomer (%-yield) Additive dimer (%-yield) Ref. 

When dicobalt octacarbonyl is added to the silane prior to olefin addition, the activity of the system is drastically reduced 13, 14). 

It might be expected that the aromatic character of (14) would lend unique characteristics to its chemistry. Studies of the olefin addition and C—H insertion reactions of the carbene, however, indicate that it is poorly stabilized and highly reactive.<26)... 

However, the photolysis of methylmercuridiazoacetate in olefins proceeds cleanly to olefin addition products from the intermediate carbene in 70-90% yields<38) ... 

Carboalkoxymethylenes, like acylmethylenes, undergo rearrangement to ketenes as well as the olefin addition and C—H insertion reactions characteristic of methylenes.<37> Thus the photolysis of ethyl diazoacetate in olefinic solvents leads to substantial yields of products, which can be rationalized in terms of a Wolff rearrangement of the carboethoxymethylene followed by cycloaddition of the resulting ethoxyketene to the olefin ... 

TV-Substituted amides and lactams possess potentially reactive C—H bonds on carbon atoms alpha to the nitrogen and carbonyl group. These hydrogen atoms are easily abstracted by excited carbonyl compounds (e.g., acetone or benzophenone) to produce radicals which undergo olefin addition <9a,98 97) ... 

In the photoaddition of 2-pyrrolidone the 5-alkyl isomer (69) always predominates, usually in a ratio of 2 1. The formation of anti-Markovnikov 1 1 adducts, telomers, and dehydrodimers of structure (71) supports a free radical mechanism. Similarly, formamide undergoes olefin addition under... 

The resulting material is active for the gas phase epoxidation of simple olefins. Addition of cyclohexene resulted in the formation of cyclohexene oxide as the sole volatile product, detected by GC/MS. 

The remarkable generality of FERET to predict the behavior of Br2 in aromatic bromination as well as in olefin addition is established by the single linear correlation in Fig. 21b when the solvation difference (see equation (103)) between the cation radicals of arene and olefin donors is taken into account.263... 

The quantitative treatment of the electron-transfer paradigm in Scheme l by FERET (equation (104)) is restricted to the comparative study of a series of structurally related donors (or acceptors). Under these conditions, the reactivity differences due to electronic properties inherent to the donor (or acceptor) are the dominant factors in the charge-transfer assessment, and any differences due to steric effects are considered minor. Such a situation is sufficient to demonstrate the viability of the electron-transfer paradigm to a specific type of donor acceptor behavior (e.g. aromatic substitution, olefin addition, etc.). However, a more general consideration requires that any steric effect be directly addressed. 

The photocycloaddition of an aldehyde or ketone with an olefin to yield an oxetane was reported by Paterno and Chieffi in 1909. 58> Contemporary studies on the synthetic utility and mechanistic features were initiated nearly 50 years later by Biichi et al. 59) Two review articles summarizing synthetic aspects of Paterno-Biichi reactions have been published 6.12)) and mechanistic studies have been reviewed several times. 6,38,60-62) The reaction involves the addition to olefin of a photo-excited carbonyl moiety. This circumstance makes it advantageous to review this reaction before a discussion of olefin-olefin additions, because the solution photochemistry of carbonyl compounds is probably better understood than any other aspect of organic photochemistry. Many of the reactions of carbonyl compounds have been elucidated during studies of the important phenomena of energy transfer and photosensitization. 63-65)... 

Polycyclic oxetanes are obtained in good yields in intramolecular carbonyl-olefin cycloadditions, in an analogous way as the corresponding alicyclic systems are formed in intramolecular enone-olefin additions. Two applications are given in (4.78)492) and in (4.79)493). 

It should be noted here again that the catalytic reaction does not involve a change of valence of the metal. In general, catalytic olefin addition reactions that involve a hydride transfer do not require change of valence in the metal catalyst. On the other hand, carbon-carbon bond formation by coupling reactions which involve electron shifts, such as in Wilke s Ni°-catalyzed butadiene oligomerization reaction [Eq. (1)], requires a valence change on the metal. 

The addition of a cation to an olefin to produce a carbonium ion or ion pair need not end there but may go through many cycles of olefin addition before the chain is eventually terminated by neutralization of the end carbonium ion. Simple addition to the double bond is essentially the same reaction stopped at the end of the first cycle. The addition of mineral acids to produce alkyl halides or sulfates, for example, may be prolonged into a polymerization reaction. However, simple addition or dimerization is the usual result with olefins and hydrogen acids. The polymerization which occurs with a-methyl-styrene and sulfuric acid or styrene and hydrochloric acid at low temperatures in polar solvents is exceptional.291 Polymerization may also be initiated by a carbonium ion formed by the dissociation of an alkyl halide as in the reaction of octyl vinyl ether with trityl chloride in ionizing solvents.292... 

Agreement is somewhat poorer for substituted hexatrienes. Consider now the ( )-isomer of 2,5-dimethyl-l,3,5-hexatriene (81) for which Roth gives an enthalpy of formation of 95.8 kJ mol-1. Simple olefin additivity, as done above for the parent hexatriene, results in a value of 103 kJ mol-1. Modifying the above 5 to 3.5 kJ mol-1 as found for the relatedly branched conjugated diene (isoprene, 82) gives a new value of ca 100 kJmol-1 for the enthalpy of formation of 81. The discrepancy has shrunk to ca 4 kJmol-1. 

Consider now the 1,1,6,6-tetramethylated derivative of (Z)-l,3,5-hexatriene (83), a species more properly named (Z)-2,6-dimethyl-2,4,6-octatriene and occasionally and trivially called ds-allo-ocimene . To estimate its enthalpy of formation, let us use simple olefin additivity along with ... 

Paulsen, H., Greve, W., and Kuhne, H., Zuckerphosphonate durch Olefin-addition und Abramov-reaktion, Tetrahedron Lett., 2109, 1971. 

This observation may well explain the considerable difference between metal-olefin and metal-acetylene chemistry observed for the trinuclear metal carbonyl compounds of this group. As with iron, ruthenium and osmium have an extensive and rich chemistry, with acetylenic complexes involving in many instances polymerization reactions, and, as noted above for both ruthenium and osmium trinuclear carbonyl derivatives, olefin addition normally occurs with interaction at one olefin center. The main metal-ligand framework is often the same for both acetylene and olefin adducts, and differs in that, for the olefin complexes, two metal-hydrogen bonds are formed by transfer of hydrogen from the olefin. The steric requirements of these two edgebridging hydrogen atoms appear to be considerable and may reduce the tendency for the addition of the second olefin molecule to the metal cluster unit and hence restrict the equivalent chemistry to that observed for the acetylene derivatives. 

An alternative LIS scheme is one in which a vibrationally excited molecule reacts preferentially with another species. An example is the hydrogen halide/olefin addition reaction, DX + RiR2C = CH2 RiR2CXCH2D. The scheme involves sequential absorption of several quanta from a C02 laser near 5 p,m to selectively excite DX to a vibrational quantum number of 3 or more. Successful implementation would be expensive because of the highly corrosive nature of halogen acids. 

If anions R are oxidized in the presence of olefins, additive dimers (24) and substituted monomers (26) are obtained (Scheme 5, Table 8, and Ref. [94]). The products can be rationalized by the following pathway the radical R obtained by a le-oxidation from the anion R adds to the alkene to give the primary adduct (25), which dimerizes to afford the additive dimer (24) with regiospeciflc head-to-head connection of the two olefins, or couples with R to form the additive monomer (26). If the substituent Y in the olefin can stabilize a carbenium ion, (25) is oxidized to the cation (27), which reacts intra- or inter-molecularly with nucleophiles to give (28) or (29). 

---