Alkenes chlorotris rhodium

Halpern J, Okamoto T and Zakhariev A 1976 Mechanism of the chlorotris(triphenylphosphine)rhodium(l)-catalyzed hydrogenation of alkenes J. Mol. Catal. 2 65-9... 

Acyl chlorides containing an a hydrogen are smoothly converted to alkenes, with loss of HCI and CO, on heating with chlorotris(triphenylphosphine)rhodium, with metallic platinum, or with certain other catalysts. The mechanism probably involves conversion of RCH2CH2COCI to RCH2CH2—RhCO(Ph3P)2Cl2 followed by a concerted syn elimination of Rh and H. See also 14-39 and 19-12. 

Not all decarbonylations give the expected product, and the relative yields are influenced by the rhodium catalyst employed. Chlorotris(triphenylphosphme)rhodium(I) rapidly and selectively decarbonylated the en /o-norbomene isomer shown in equation (4) to form a tricycline product, but [Rh(dppp)2]Cl additionally forms an isomeric alkene. In the case of the corresponding exo-isomer (equation 5), [RhCl(PPh3)3] is the less selective catalyst. It was also found that [Rh(dppp)2]Cl was a superior catalyst... 

Some catalysts suffer a different type of alkyne poisoning. Chlorotris(triphenylphosphine)rhodium(I) is an effective terminal alkyne polymerization catalyst. When this complex is used in the reduction of these alkynes, it gradually loses its activity because of the competing polymerization reaction. Even initially the rate of alkyne hydrogenation is much slower than that of the corresponding alkene because of the greater binding constant of the former substrate. 

The fu-st example of rhodium catalysis for this purpose utilized chlorotris(triphenylphosphine)rho-dium(I) to catalyze the allylic oxidation of a range of alkenes. - This catalyst has also been shown to successfully oxidize cyclic allylsilanes to afford p-silyl-2-cycloalkenones in very good yields and with exclusive rearrangement (equation 43). 

Scheme 6.14. A representation of the reduction of an alkene with hydrogen (H2) and chlorotris(triphenylphosphine)rhodium (ClRh[(C6H5)3P]3).

Rh-Catalyzed Hydrosilylation of Alkenes. Treatment of 2-p3Tidyldimethylsilane with 1-alkenes in the presence of a catalytic amount of chlorotris(triphenylphosphine)rhodium gives ter-... 

Substituted v-butyrolactones can be prepared by reaction of aldehydes or ketones with tbe dianion (28), and direct condensation of symmetrical ketones with diethyl 2-oxomalonate provides a useful synthetic route to the butenolides (29). A number of initiators have been used previously to promote the free-radical addition of ketones to alkenes now transition-metal oxides have been shown to be effective. Pent-4-enal is cyclized to cyclopentanone by chlorotris(triphenylphos-phine)rhodium(i) through a non-radical pathway. ... 

Chlorotris(triphenylphosphine)rhodium(i) can also catalyse hydrogen transfer from dioxan to an alkene. The rate-determining step in this reaction is considered to be oxidative addition of C—bonds of dioxan to the catalyst ... 

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