Propene reaction with methyl complexes

A similar study was done with methyl acrylate as the dienophile.28 The uncatalyzed and catalyzed TSs are shown in Figure 6.7. As with propenal, the catalyzed reaction is quite asynchronous with C(2)-C(3) bonding running ahead of C(l)-C(6) bonding. In this system, there is a shift from favoring the exo-s-cis TS in the thermal reaction to the endo-s-trans TS in the catalyzed reaction. A large component in this difference is the relative stability of the free and complexed dienophile. The free dienophile favors the s-cis conformation, whereas the BF3 complex favors the s-trans conformation. 

The development of Ir-chiral N,P ligand system opens another promising way for the hydrogenation of allylic alcohol and its derivatives. For example, a cationic Phox-Ir complex catalyzes the hydrogenation of ( )-2-methyl-3-phenyl-9-propen-l-ol in a highly enantioselective fashion.178 With 1 mol.% (5)-92-Ir catalyst, the hydrogenation proceeds completely to provide the chiral alcohol product in 96% ee. Under the same conditions, a para- Bu-substituted chiral alcohol derivative is obtained with 94% ee for the synthesis of lilial (Equation (59)). Heterocyclic N, P-ligand, HetPHOX 113, is also efficient for this reaction.191... 

Intermolecular addition of carbon nucleophiles to the ri2-pyrrolium complexes has shown limited success because of the decreased reactivity of the iminium moiety coupled with the acidity (pKa 18-20) of the ammine ligands on the osmium, the latter of which prohibits the use of robust nucleophiles. Addition of cyanide ion to the l-methyl-2//-pyr-rolium complex 32 occurs to give the 2-cyano-substituted 3-pyrroline complex 75 as one diastereomer (Figure 15). In contrast, the 1-methyl-3//-pyrrolium species 28, which possesses an acidic C-3-proton in an anti orientation, results in a significant (-30%) amount of deprotonation in addition to the 2-pyrroline complex 78 under the same reaction conditions. Uncharacteristically, 78 is isolated as a 3 2 ratio of isomers, presumably via epimerization at C-2.17 Other potential nucleophiles such as the conjugate base of malononitrile, potassium acetoacetate, and the silyl ketene acetal 2-methoxy-l-methyl-2-(trimethylsiloxy)-l-propene either do not react or result in deprotonation under ambient conditions. 

IR, Raman and 13C NMR spectroscopic studies have been performed on various [Ir(acac)(L)2] complexes (L = ethylene, propene, vinyl chloride, vinyl acetate, methyl acrylate, styrene) for the elucidation of the bonding between Ir and the alkene ligand.142 Also, the square planar iridium(I) acetylacetonate complexes [Ir(LL)(L )2], where LL is a /J-diketonate and L is CO or ethylene, have been studied by UVPES.143 The enthalpies of reaction of the crystalline [Ir(acac)(L)2] complexes with gaseous CO (reaction 28) have been determined by differential scanning calorimetry. The enthalpies for the gaseous reaction have been derived from these results and Ir—L bond strengths estimated.143... 

Reaction of Methyl Complexes with Propene. Products. 

A typical reaction involving nickel(O) treats an allylic halide such as 3-chloro-2-methyl-l-propene with Ni(CO)4 to form 439,288 a nickel dimer analogous to the palladium chloride dimer discussed in the previous section. This complex reacts with an alkene to form a new complex (440), and subsequent reaction with a variety of electrophilic reagents removes nickel. In this example, the chlorine was converted to an acetate ligand (in 441) and reacted with methanolic carbon monoxide to give the ester (442).288... 

The results of ab initio calculations for the addition of borane to ethene depend on the level of the calculation. " For the reaction of borane with propene in the gas phase, Houk and co-workers identified a n complex and two transition states, one for attachment of the boron atom to the carbon bearing two hydrogen atoms and one for attachment of the boron atom to the methyl-substituted carbon atom. As in the case of ethene, the n complex formed from propene was found to be lower in energy than the reactants. The transition state for attachment of the boron atom to the CH2 position was found to be 3.7 kcal/mol lower in energy than the alternative transition state, and the difference in energy was attributed to a combination of electronic and steric factors. ... 

Other Metals.—Photochemical or thermal displacement of CO from (ij -allyl)Mn(CO)4 with PX3 (X=R or OR) yields ( -allyl)Mn(CO)2(PX3)2 and (rj3.allyl)Mn(CO)(PX 3) 3 complexes. N.m.r. studies of the latter at low temperature indicate a pseudo-octahedral geometry with rram-phosphorus atoms. C studies of ( -allyl)Mn(CO)4 have also been reported, but quadrupole relaxation by the Mn prohibits any determination of the mechanism of fluxionality. Reaction of [V(CO)4L2] with allyl halides yields ( -allyl)V(CO)3L2 complexes (La = diars or arphos). Similar ( j -methylallyl)V(CO)3L2 complexes (La=arphos or dppm) may be prepared by reaction of isoprene with HV(CO)4La isomers with methyl groups in different positions are obtained. Reaction of CpaTaCla with RMgCl yields Cp2Ta(H)(olefin) complexes (olefin=propene, but-l-ene, pent-l-ene, or cyclopentene). The olefin is easily displaced by phosphine, and the complexes react with Ha to give CpaTaHs. ... 

Another type of elimination reaction is the reaction of 1 -(5-methyl-1 -phenyl- H-pyrazol-4-yl)ethanone with a Vilsmeier complex to give 3-chloro-3-(5-methyl-l-phenyl-l//-pyrazol-4-yl)propenal, which in turn undergoes dichloroformylation... 

To a solution of hexamethyldisilane (2.5 mmol) in HMPA (CAUTION— CANCER SUSPECT AGENT) (3 ml) at 0-5 °C was added methyl lithium (2.5 mmol, 1.5 m MeLi.LiBr complex in ether) dropwise. After being stirred for 3 min, the red solution was treated with Cul (2.5 mmol) in Me2S (1 ml), the resulting black reaction mixture was stirred for 3 min. and 2,3-dibromo-propene (1 mmol) was added rapidly via a syringe. The reaction mixture was allowed to warm to room temperature, and was stirred for 1.5 h. It was then poured into pentane (25 ml) and saturated ammonium chloride solution (25 ml, buffered to pH 8 by the addition of ammonium hydroxide), and the mixture was stirred vigorously for 1 h. The aqueous phase was re-extracted with pentane, and the combined organic extracts were dried. Removal of... 

In a more complex type of reaction, propene reacts with methyl trichloro-acetate under the catalytic influence of cyclopentadienylmolybdenum tricarbonyl or cyclopentadienyliron dicarbonyl dimers to give 4-methyl-2,2 -... 

The experimental evidence which has accumulated in recent years shows that in every system which has been rigorously investigated the polymerization of olefins by metal halides depends upon the presence of some third substance, the co-catalyst [2-8]. The function of the cocatalyst is to provide the ions which start the polymerization proper, by forming an ionogenic complex with the metal halide. In most systems the metal halide is not consumed in the course of the reaction, so that the term catalyst in its classical sense may be retained in this respect. Exceptions to this are some polymerizations involving aluminum halides in the polymerization of propene [9], and possibly of styrene and a-methyl styrene [10], these catalysts may be inactivated by the formation of stable complexes. In other cases, such as the... 

Copper(II) complexes of amino acids have been explored as chiral Lewis acid catalysts in the Diels-Alder reaction of 3-phenyl-l-(2-pyridyl)-2-propen-l-one with cyclopentadiene. The best results were obtained using /V-methyl-/.-tryptophan, but more interestingly, the highest ee values for the major endo adduct were achieved in aqueous solution273. 

Many examples of the use of chiral Ca-symmetric bis(oxazoline) hgands have been presented here. Other examples include their use in various heteroannulations, one of which is shown in Figure 9.69. Here, the vinyl iodide, (Z)-3-iodo-2-methyl-2-propen-l-ol, 235 is condensed with 1,2-undecadiene to form the 3-methylene-2//-pyran derivative 237. " When this reaction was mn in the presence of 10 mol% of bis(oxazoline) Ugand 236 complexed with palladium(ll), 237 was produced in 70% yield with 79% ee. 

Scheme 21. The gas-phrase reactions of CoO+ with 2-methylpropane (iso-butane). Note that the compound labeled A is a 2-methyl-l-propene (iso-butylene) complex of Co , while the compound labeled B is a trimethylenemethane complex of Co. ...

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