Alkenes terminal aliphatic

Addition of a phosphorus-sulfur bond to a carbon-carbon triple bond is catalyzed by a palladium(O) complex (Equation (130)).298 Terminal aliphatic alkynes having various functional groups undergo the addition with PhS-P(0)(OPh)2 to afford (Z)-adducts in high yield. In contrast to aliphatic alkynes, phenylacetylene gives a mixture of E Z adducts. Internal alkynes and alkenes are unreactive. 

We therefore evaluated how the bite angle affected regioselectivity, and studied the counterbalance of non-bonding and orbital effects. We choose two diphosphine ligands (benzoxantphos and homoxantphos) which among the series of xantphos ligands represent the extreme cases of natural bite angle, and used propene as a model for terminal aliphatic alkenes and styrene. 

In the absence of an oxidation agent, the reaction is derived to monoalkoxy-carbonylation provided the Pd metal center is stabilized by surrounding ligands. This strategy, first illustrated in 1976 by Knifton with the complex [PdCl2(PPh3)2], has been extensively developed since then [55,56]. Various terminal aliphatic alkenes are converted into the corresponding mono esters... 

Non-heme iron catalysts containing multidentate nitrogen ligands such as pyri-dines and amines have been studied by various groups [42a, 52-54], Jacobsen and coworkers presented an MMO mimic system for the epoxidation of aliphatic alkenes in which the catalyst self-assembles to form the active species [54] (Scheme 3.5). Interestingly, small amounts of an additive (one equivalent of acetic acid) increased the catalytic performance, presumably due to the intermediate formation of peroxya-cetic acid [55, 56]. The reactions proceeded quickly even with terminal aliphatic alkenes, which are generally considered difficult substrates. Another catalyst system available for the epoxidation of terminal alkenes uses phenanthroline as ligand [57]. 

We have recently broadened those investigations to study the origin of the enantioselectivity in the dihydroxylation of terminal aliphatic n-alkenes. The dihydroxylation of the series from propene to 1-decene was studied by means of the IMOMM method [97]. Experimental studies on propene, 1-butene, 1-pentene, 1-hexene and 1-decene showed that the reaction was enantioselec-tive in all cases, leading to the R product. Moreover, the results show a dependence of the enantioselectivity on the chain length it sharply increases from propene to 1-pentene, and after that the enantioselectivity remains practically constant for 1-hexene and 1-decene. The explanation for this dependence of the enantioselectivity with the chain length remained elusive. On the other hand, the -stacking interactions that were found to be critical for styrene cannot be responsible for the observed enantioselectivity for these terminal aliphatic n-alkenes because they do not have aromatic rings. 

Metal mediated epoxidahon is remarkably diverse, with many types of ligand systems being represented. For example, a cytochrome P450 BM-3 mutant (139-3) has been developed using directed evolution, which exhibits high activity towards epoxidation of several non-natural substrates. Thus, exposure of styrene 4 to BM-3 variant 139-3 in phosphate buffer containing methanol and NADPH resulted in the quantitative conversion to styrene oxide 5. For terminal aliphatic alkenes, however, allyhc hydroxylation is the predominant process <04T525>. 

The reaction of "BrF generated from these reactants has been extended to terminal aliphatic alkenes to give inV. -fluorobromides.4 An example is the preparation of l-bromo-2-fluoroheptane.5 The products are convertible, as shown for the case of l-bromo-2-fluoroheptane.6 into a-fluoroalkanoic acids.7... 

Similar unsatisfactory results, usually with even lower inductions are obtained with other terminal aliphatic alkenes such as 1-pentene, 2-methy]-l -butene, 3-methyl-l -butene, 2,3-dimethyl-l-butene, 3,3-dimethyl-l-butene, 2,3,3-trimethyl-l-butene, 2-ethyl-l-hexene, I-hex-ene and 1-octene (Table 1). 

The study was broadened by the same authors to the investigation of the origin of the enantioselectivity in the dihydroxylation of terminal aliphatic n-alkenes. The dihydroxylation of the series from propene to 1-decene was studied by means of the IMOMM method [71]. Experimental studies on propene,... 

Very recently, Reiser showed that a his(isonitrile) ligand forms robust Pd(II) complexes for the direct Wacker oxidation of alkenes without Cu co-catalysts under 1 atm of O2 at 70°C. The catal5dic system showed good activity towards terminal aliphatic alkenes, hut also styrene substrates, which are usually more challenging substrates for this kind of oxidation because of the competitive double-bond cleavage under oxidative conditions reacting readily, favoring the acetophenone products and concomitant formation of benzaldehydes as side products in 4-20% yield (Scheme 23.48). 

The dihydroxylatiOTi of terminal aliphatic n-alkenes (propene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene and 1-decene) catalyzed by osmium tetroxide, a powerful method to enantioselectively introduce chiral centres into organic substrates, has been computationally studied by the hybrid QM/MM IMOMM-(B3LYP MM3) method. The analysis of the results, in particular the partition of the total IMOMM energy into its components, allows the responsibility for the selectivity to be identified [690]. 

Drudis-Sole G et al (2005) A QM/MM study of the asymmetric dihydroxylatimi of terminal aliphatic n-alkenes with 0s04(DHQD)2PYDZ enantioselectivity as a function of chain length. Chem-Eur J 11 1017-1029... 

For ffie past several decades, several chemocatalysts and biocatalysts have been used for ffie epoxidation of nonfunctionalized aliphatic alkenes. The Katsuki-Jacobsen epoxidation, which is catalyzed by chiral Mn(III)-salen with NaOCl/PhIO as an oxidant, achieves good yields and high stereoselectivities (84-94%ee) for ffie epoxidation of ds-alkenes [21]. The Shi epoxidation, which is catalyzed by ffie fructose-derived ketone and oxone, has been successfully used in ffie epoxidation of frans-alkenes, yielding ffie corresponding oxides with 93-98% ee [74]. However, for nonfunctionalized terminal aliphatic alkenes, chemocatalysts typically display low stereoselectivity [7]. 

Most recently, Zhdankin described that the combination of catalytic amounts of tetrabutylammonium iodide (TBAI) with m-chloroperoxybenzoic acid (mCPBA) as a terminal oxidant [77] was the effective catalyst system for the aziridination of various types of alkenes (Scheme 2.53) [78]. The reaction of styrenes with either electron-donating or electron-withdrawing groups afforded the desired aziridines in good yields. Cyclic alkenes and aliphatic alkenes such as 1-decene... 

The above-postulated overall mechanism considers two alternative pathways depending on the nature of the acetylene derivative. Region A outlines a proposal in which the formation of the a-complex intermediate is supported by the fact that the treatment of aliphatic terminal acetylenes with FeCl3 led to 2-chloro-l-alkenes or methyl ketones (Scheme 12). The catalytic cycle outlined in region B invoked the formation of the oxetene. Any attempt to control the final balance of the obtained... 

Various metal complexes catalyze the addition of catecholborane and pinacolbo-rane to aliphatic terminal alkenes (Table 1-2). Neither the borane reagents nor the catalysts alter the high terminal selectivity, but a titanium catalyst does (entry 3). Although Cp2TiMe2 [30] exhibits high terminal selectivity for vinylarenes, aliphatic alkenes afford appreciable amounts of internal products, whereas an analogous Cp 2Sm(THF) [31] allows selective addition of catecholborane to the terminal car-... 

The phosphine-based platinum(O) catalysts do not catalyze the diboration of alkenes because of the high coordination ability of phosphine over the alkene double bond, but platinum(O) complexes without a phosphine ligand such as Pt(dba)2 [128] and Pt(cod)2 [129] are an excellent catalyst allowing the alkene insertion into the B-Pt bond under mild conditions (Scheme 1-30). The diboration of aliphatic and aromatic terminal alkenes takes place smoothly at 50°C or even at room temperature. The reaction is significantly slow for disubstituted alkenes and cyclic alkenes, but cyclic alkenes having an internal strain afford ds-diboration products in high... 

Silyl(pinacol)borane (88) also adds to terminal alkenes in the presence of a coordinate unsaturated platinum complex (Scheme 1-31) [132]. The reaction selectively provides 1,2-adducts (97) for vinylarenes, but aliphatic alkenes are accompanied by some 1,1-adducts (98). The formation of two products can be rationalized by the mechanism proceeding through the insertion of alkene into the B-Pt bond giving 99 or 100. The reductive elimination of 97 occurs very smoothly, but a fast P-hydride elimination from the secondary alkyl-platinum species (100) leads to isomerization to the terminal carbon. 

Nitroxyl radicals (AmO ) are known to react rapidly with alkyl radicals and efficiently retard the radical polymerization of hydrocarbons [7]. At the same time, only aromatic nitroxyls are capable of reacting with alkylperoxyl radicals [10,39] and in this case the chain termination in the oxidation of saturated hydrocarbons occurs stoichiometrically. However, in the processes of oxidation of alcohols, alkenes, and primary and secondary aliphatic amines in which the chain reaction involves the HOT, >C(0H)02 , and >C(NHR)02 radicals, possessing the... 

Addition of diphenyl disulfide (PhS)2 to terminal alkynes is catalyzed by palladium complexes to give l,2-bis(phe-nylthio)alkenes (Table 3)168-172 The reaction is stereoselective, affording the (Z)-adducts as the major isomer. A rhodium(i) catalyst system works well for less reactive aliphatic disulfides.173 Bis(triisopropylsilyl) disulfide adds to alkynes to give (Z)-l,2-bis(silylsulfanyl)alkenes, which allows further transformations of the silyl group to occur with various electrophiles.174,175 Diphenyl diselenide also undergoes the 1,2-addition to terminal alkynes in the presence of palladium catalysts.176... 

Thiols catalyse radical-chain addition of primary aliphatic aldehydes (R CH2CH0) to terminal alkenes (H2C=CR R ) to give ketones, R CH2C0CH2CHR R. The thiol acts as an umpolung catalyst to promote the transfer of the aldehydic hydrogen to the carbon-centred radical formed when an acyl radical adds to the alkene. 

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