Cyclopropanes reactions with

Scheme 1.20 Test reaction with cyclopropane-based S/P ligands.

Thus, reactions affording either cyclopropanes or propylenes would most likely represent forms of termination of metathesis activity. As a corollary, any catalytic conversion of cyclopropanes to metathesis olefins via Eq. (26) would seem to require decomposition of the metal-carbene species in order to regenerate a naked metal species (M ) capable of further reactions with cyclopropanes. Of course, bimolecular carbene decomposition to yield an olefin as in Eq. (11) (e.g., ethylene from 2M=CH,) is one accepted process which could account for regeneration of M ... 

It was also suggested that the fragmentation of the excited C3HeT+ ions which escape stabilization occurs predominantly according to processes (59) and (60). These produce, in addition to tritiated methane, labeled vinyl and allyl ions, whose consecutive reactions with cyclopropane lead to the formation of tritiated ethylene by two different routes ... 

Marks has examined the reactivity of thorium metallacycles with hydrocarbons, where ring strain is used to provide the thermodynamic driving force for alkane activation in a reaction with methane (Eq. 17). Reaction with CD4 shows a dramatic kinetic isotope effect, with kH/kD=6, which is typical of the four-centered electrophilic transition state hydrocarbon activations [76]. The metallacy-cle is formed by the elimination of neopentane from the bis-neopentyl derivative [77]. Reaction with cyclopropane and tetramethylsilane gave the bis-cyclopropyl product Cp 2Th(c-propyl)2 and the bis-TMS product Cp 2Th(CH2SiMe3)2, respectively [78]. 

A titanabicyclo[2.1.0]pentane system 23 was formed from 3,3-dimethylcyclopropene and the precursor of Tebbe s reagent. Among various reactions with cyclopropane ring opening, release of 1,1,2-trimethylcyclopropane (89%) was reported to occur upon treatment with hydrochloric acid. ... 

Reaction with cyclobutanes 5.8.2.14 Reaction with cyclopropanes 5.8.12.4 Reaction with cyclopropanes and cyclobutanes 5.8.2.14... 

A striking feature in the above experiments is the observation that C3D6H2 formed in the reaction with cyclopropane-dg has the structure CD2HCD2CD2H, The result indicates that cyclopropane behaves as an olefin rather than an alkane in these reactions, and that the reaction proceeds via a well-defined loose complex such as... 

In all the experiments involving deuterium to be described here, there was an extensive formation of HD by exchange processes, and this necessitated the use of large excesses of deuterium to prevent its further reaction. Nevertheless, its introduction into the deuterium always caused the proportions of the various deuteropropanes to vary as the reactions proceeded, and they were therefore taken only to small conversion wherever possible. Extrapolation procedures were then used to arrive at the distribution of deuterium among the propanes at zero conversion, and results in subsequent tables are quoted as such. The propanes are expressed as fractions of those containing from two to eight deuterium atoms the yields of propane-do and propane-di from reactions with cyclopropane were normally very small, but in reactions with propane, that of propane-di was sometimes considerable. 

Pd(PhC=CCOC=CHPh)Vdppm 8, 4.S.3.6.2 PdCl2(NCCf,H.,)2 Generation from 14, 9.2.4.1 Reaction with alkynes 14, 11.6.2 Reaction with cyclopropanes 14, 11.6.7 PdCl2(PhCN)2... 

A possible mechanism for scavenging reaction with cyclopropane is the H2" transfer [8]. 

Higher alkanes undergo exothermic gas-phase reactions with some transition-metal ions. Co" and Ni insert into the C—C and C—H bonds of propane to give oxidative addition products which eliminate CH4 and H2, respectively. The relative amount of methane formed increases with the amount of branching in the alkane . LaFe" reacts with alkanes (except methane) giving mainly dehydrogenation products, but with some C—C cleavage, particularly in reactions with cyclopropane and cyclobutane... 

The reaction with cyclopropane gives acetylene and ethylene. 

The reaction with cyclopropane and cyclohexane appears to be the slowest due to the increase in energy cycle upon s[ —> sff transition. In the other cases the energy decreases and this leads to raise of the reaction rates. 

Insertion into the C—C bond. According to ab initio calculations with an extended basis set of the 6-3IG type and the correlation energy taken into account [66], the energy profile of insertion of methylene into the single C—C bond is, in the main, determined by steric factors. So the activation barrier for insertion into the C—C bond of ethane is very high (46 kcal/mol). At the same time, a similar reaction with cyclopropane must proceed with hardly any activation (a mere 2 kcal/mol). Upon insertion into a strained cycle C—C bond whose electron density exhibits a maximum off the bond line, strong electron interactions become possible at longer inter-nuclear distances, so the authors of Ref [66] hold that such an insertion should proceed with no activation barrier. Table 8.4 contains calculated data on reactions of carbene insertion into some other bonds of the X—H type. 

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