Alkene also hydride route

Under the same conditions, several types of hydrocarbon are also converted to fully deuterated compounds. The results are summarized in Table 1. Cydooctene was also transformed into fully deuterated cydooctene without a skeletal rearrangement. As shown in entries 2 and 3, saturated hydrocarbons have also been transformed into fully deuterated compounds. As described above, an interaction between allylic C-H bonds and palladium hydride induces the H-D exchange reaction for alkenes. H-D exchange in alkanes, however, cannot be explained in this way. Direct C-H activation without assistance from any functional group may be a route to the formation of fully deuterated alkanes. 

These are generally limited to what are termed kinetically stabilized alkyls, i.e. those devoid of protons p to the metal (Figure 4.5). These also include norbornyl and adamantyl examples since decomposition via p-metal hydride elimination (see below) would require the installation of an alkenic bond between the a and p carbons of the precursor alkyl. This is precluded for these two alkyls because of the prohibitive strain associated with forming a double bond to a bridgehead atom within a small cage structure (Brendt s rules). The tetrakis(norbornyl) complexes are also remarkable because some uncharacteristic oxidations states can be attained, e.g. Cr(IV), Co(IV) (low-spin e4t2°). The second factor which may confer stability is steric bulk bimolecular decomposition routes are thereby discouraged. 

The conversion of alkenes into epoxides is important not only because it is one of the most reliable routes leading from oxidation level 1 to level 2, but also because reactions of non-symmetrical epoxides with nucleophiles invariably proceed as an attack at the less substituted carbon with inversion of configuration. Thus, hydride reduction of epoxides represents an additional option for the preparation of alcohols (Scheme 2.62), especially valuable for the synthesis of optically pure isomers from epoxides obtained by the Sharpless oxidation. It is also of merit that as a result of alkene-epoxide conversion, a nucleophilic moiety (double bond) is transformed into an electrophilic epoxy ring. The latter... 

The regenerated carbonium ion can of course continue the process, a key feature being that under alkylation conditions this active species is formed from saturated alkane, not an olefin as required by polymerization. Different alkenes, such as propylene, 1-butene, or the 2-butenes may also form carbonium ions in a similar manner to the process of Eq. 18.25. However, neither /7-butane nor /7-pentane can replace an isoalkane for the hydride transfer since an /7-alkane is not capable of forming a stabilized carbonium ion. Nevertheless, this is one advantage that the alkylation process has over polymerization as a route to gasoline it is able to use both light hydrocarbon alkanes (as long as they are branched) and alkenes. Alkylation and polymerization both produce branched products, but the alkylation products are saturated (Table 18.5) whereas the polymerization products are alkenes. 

The protonated form of Fp can add to conjugated carbonyl derivatives such as acrylonitrile596 and also with conjugated dienes.597 Both S03598 and carbon monoxide can be inserted into the Fe—C bond of FpR.598 Protonolysis provides a synthetic route to substituted nitriles or alkenes. In each case the Fp unit can also be removed photochemically, thermally, or by treatment with triphenylphosphine. Hydride extraction to give an alkene or a diene is also known.599... 

Salts of imidazoles can be alkylated or acylated on nitrogen. One convenient method is to use the dry sodium/potassium salt obtained by evaporation of an aqueous alkaline solution sodium hydride in dimethylformamide also serves very well for this purpose. When there is a route for the entering group to be lost again, as in the addition to a carbonyl-conjugated alkene, a 2,4(5)-substituted imidazole will give the less hindered 1,2,4-trisubstituted product rather than the 1,2,5-isomer.The use of... 

In a similar way to the synthesis of Pt( 7 -alkene)(dfepe), treatment of the hydride dimer [Pt(/t-H)(dfepe)]2 with alkynes (R CfeCR ) affords Pt( 7 -R C R )(dfepe). In the reaction with propyne, a small amount of the dimer Pt(dfepe)2 2()t" - "M C GH) is also formed. Selective hydride transfer in PtH(dppe)MCp(CO)3 (M = Mo, W) was induced with disubstituted alkynes to yield Pt(77 -alkyne)(dppe) and MHCp(CO)3. " With diphenylacety-lene, the / -hydrogen elimination is found to be a reversible process. A new synthetic route to Pt( 7 -PhC Ph)2 based on the reduction of m-[PtCl2(7 -PhCH=CH2)2] with SiHPh3 in the presence of PhC Ph has been reported. The reaction of /ra j-[PtHCl(PPh3)2] with l,l-diphenyl-2-propynol in the presence of NEt2H affords... 

Carbopalladation of dienes yields 7r-allylpalladium intennediates capable of capturing nucleophiles. An example of this type of reaction in natural product synthesis is the conversion of the aryl iodide 168 into pentacycle 169. After 6-exo carbopalladation the free phenol is captured by the resultant Tr-allylpaUadium intermediate to yield aUyUc ether 169 en route to (-)-morphine 120. The domino reaction closes a srx-membered ring, forges a quaternary center, and forms a five-membered furan ring. The reaction sequence has also been effectively reversed in a construction of (+)-y-lycorane 172. Treatment of aUylic benzoate 170 with a palladium catalyst in the presence of sodium hydride triggers tt-allylpalladium formation and intramolecular amide capture. rr-Allylpalladium formation occurs with inversion, as does reaction with the pendant amide, resulting in a net retentive 1,3-transposition of stereochemical information. Subsequent addition of base and thermolysis induces 6-exo intramolecular carbopalladation to yield alkene 171. 

Zirconocene alkene complexes 29 are readily prepared by the p-hydride activation route from dialkyl zirconocenes 28 or methyl alkyl zirconocenes 27 (Scheme 5.10). It is also possible to prepare the zirconocene complexes of ethene, styrene, and, to a lesser extent, vinyltrimethylsilane by displacement of the weakly bound 1-butene ligand from 4. ... 

An improved procedure for the synthesis of alkyl iodides from organoboranes (and thus ultimately from alkenes), involving the use of iodine and sodium meth-oxide, has been shown to entail inversion at the C-B bond, and is employed in a new route to optically active iodides from alkenes e.g. Scheme 30). A similar sequence for conversion of alkenes to primary halides via hydrozirconation (Scheme 31) has been reviewed. Zr also catalyses addition of lithium aluminium hydride to alkenes under mild conditions, and the alanes so formed can likewise be converted into alkyl halides (Scheme 32). 

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