Skeletal Rearrangement Reactions

Subsequent to the discovery of skeletal rearrangement reactions on plati-num/charcoal catalysts, the reality of platinum-only catalysis for reactions of this sort was reinforced with the observation of the isomerization of C4 and C5 aliphatic hydrocarbons over thick continuous evaporated platinum films (68,108, 24). As we have seen from the discussion of film structure in previous sections, films of this sort offer negligible access of gas to the substrate beneath. Furthermore, these reactions were often carried out under conditions where no glass, other than that covered by platinum film, was heated to reaction temperature that is, there was essentially no surface other than platinum available at reaction temperature. Studies have also been carried out (109, 110) using platinum/silica catalysts in which the silica is catalytically inert, and the reaction is undoubted confined to the platinum surface. 

Hypothetical (carbene)gold(i) structures of intermediates and reaction coordinates have been calculated (B3LYP/ 6-31G and LAN2DZ levels) for (H3P)Au+-catalyzed cyclization reactions of terminal enynes. The endocyclic skeletal rearrangement reactions were found to proceed exclusively via cyclopropylcarbene complexes.240... 

PtCl2 constitutes an efficient and practical catalyst for skeletal rearrangement reaction of enynes. This includes a formal enyne metathesis reaction delivering 1,3-dienes. Skeletal reorganization of enyne 75a having a carbon chain in... 

Skeletal rearrangement reactions over Pt single crystals have been studied for methyl cyclopentane, 2- and 3-methylpentane350 and for n-hexane.3sl One conclusion351 is that whereas aromatization reactions are very sensitive to surface structure [Pt(l 11)> Pt(100)], isomerization, Cs-cyclization, and hydrogenolysis reactions display little dependence on structure. Temperature and H2 pressure are more important in affecting the selectivity. 

Davis SM, Zaera F, Somorjai GA (1982) Surface structure and temperature dependence of light-alkane skeletal rearrangement reactions catalyzed over platinum single-crystal surfaces. J Am Chem Soc 104 7453... 

Eichinger, P. C. H., Dua, S., Bowie, J. H. A comparison of skeletal rearrangement reactions of even-electron anions in solution and in the gas phase. Int. J. Mass Spectrom. Ion Processes tOOi, 133,1-12. 

Rearrangement reactions, including internal nucleophilic substitution/displacement and skeletal rearrangement reactions. 

In parallel studies, other skeletal rearrangement reactions were discovered and investigated ... 

Skeletal Rearrangement Reactions of Olefins, Paraffins, and Aromatics over Aluminophosphate-Based Molecular Sieve Catalysts... 

S.M. Davis, F. Zaera, and G.A. Somoijai. Surface Structure and Temperature Dependence of n-Hexane Skeletal Rearrangement Reactions Catalyzed over Platinum Single Crystal Surfaces Marked Structure Sensitivity of Aromatization. J. Catal. 85 206 (1984). 

M. Haouas, S. Walspurger, J. Sommer, Regioselective H/D isotope exchange and skeletal rearrangement reactions of propane over strong solid acids, J. Catal, 2003, 215, 122-128. M. Haouas, S. Walspurger, F. Taulelle, J. Sommer, The initial stages of solid acid-catalyzed reactions of adsorbed propane. A mechanistic study by in situ MAS NMR, J. Am. Chem. Soc., 2004, 126, 599-606. 

The 1,2-alkyl/aryl migration reaction is found in various skeletal rearrangement reactions catalyzed by transition metals. See Section 7.2 and Ref. [90] for examples. 

Some alkenes undergo a skeletal rearrangement reaction through cleavage of C-C bonds when treated with a transition metal complex. For example, 1,4-diene 5 isomerized to 1,4-diene 9 by action of a nickel catalyst (Scheme 7.3) [4]. Mechanistically, an Ni-H species is initially generated from NiCl2[P( -Bu)3]2... 

A different skeletal rearrangement reaction of norbornadiene takes place on cobalt (Scheme 7.7) [9]. Protonation of the (norbornadiene)cobalt complex 19 induced C-C bond cleavage of the norbornenyl ring to form the cationic aUyl-cobalt complex 20. Reduction with LiBHEtj formed the neutral diene complex 21, which undergoes further C-C bond cleavage upon treatment with acid to give the T -pentadienyl complex 22. 

TT-Acidic transition-metal-catalyzed skeletal rearrangement reaction is one of the most attractive transformations for the construction of highly elaborate molecules in a single operation under mild and neutral reaction conditions [1]. A wide variety of transition-metal elements, such as Pd, Ru, Au, Pt, and Cu, have been utilized as TT-electrophilic catalyst to activate carbon-carbon multiple bonds such as... 

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