Elimination reactions, cycloalkane

In the case of iridium, complex [IrH2(PPh3)2(acetone)2] BF4 (11) was the first to carry out catalytically the dehydrogenation of cycloalkanes [13, 14]. However, it was later realized that the halocarbons used as solvents reacted with 11 to produce the stable species [HL2lr(p-Cl)2(. i-X)IrL2H]BF4 (X = Cl (14) or H (15)) [16] (Scheme 13.8), and that elimination of the solvent by running the reactions in neat alkane not only improved yields but also permitted the activation of other previously unreactive cycloalkanes, such as methyl- and ethyl-cyclopentane. However, it was also noted that the system in some cases was not catalytic, due mainly to decomposition of the catalyst at the temperatures employed [16]. 

If nitrogen is eliminated from a cyclic azoalkane by irradiation, the initially formed biradical may react by internal combination to form a smaller-ring cycloalkane. On direct irradiation this is often a highly stereoselective process (5-21), although mixtures of isomers are generally formed when triplet sensitization operates. This reaction... 

Conformation has a major influence on the chemical reactivity of cycloalkanes. To understand its effect in any one reaction, we first need to know what the conformation is of the transition state, and this requires a knowledge of the reaction mechanism. Next, we have to decide what amount of energy is required for the reactants to achieve transition-state conformations. For example, consider the E2 elimination discussed in Section 8-8D. The preferred transition state requires the leaving groups to be antarafacial and coplanar ... 

Metal nitrene complexes were used in a number of C-H amination reactions (recent reviews [358, 359]). Copper ketiminate complexes react with azides to nitrene complexes, which were isolated [360]. (p-Ketiminate)copper(I) complex 262 (2.5 mol%) serves therefore as an efficient catalyst for the intermolecular C-H amination of alkylarenes, cycloalkanes, or benzaldehydes 260 using adamantyl azide 261 as the nitrogen source ig. 68) [361]. The corresponding adamantyl amines or amides 263 were isolated in 80-93% yield. Copper complex 262 forms initially a dinuclear bridged complex with 261. From this a copper nitrene complex is generated by elimination of nitrogen, which mediates the hydrogen abstraction from 260. 

Cyclic olefins preferably undergo twofold carbonylation, even without the presence of buffer compounds such as sodium acetate. With methanol serving as the solvent and under comparable reaction conditions to those mentioned above, cycloalkenes give product mixtures consisting of methyl rrans-2-methoxy-cycloalkanecarboxylates, dimethyl cw-cycloalkane-l,2-dicarboxylates and dimethyl cw-cycloalkane-1,3-dicarboxylates (eq. (3) and Table 1). The formation of 1,3-diesters may be explained by an intermediate reaction sequence which involves an oxidative elimination and a subsequent readdition of the Pd species, thus giving rise to an isomerization [9]. 

IV.1.2.2. Syn Eliminations on transDibromo Cycloalkane Derivatives Reaction pictured in Scheme 12 may be performed by way of syn elimination. 

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