Acyclic cation

A different type of behaviour is observed with the chloro Lewis acid BCI3. With this reagent halogen exchange occurs to produce the acyclic cation [N(SC1)2] , as the [BCU] salt, rather than NSCf. " Thiazyl trichloride NSCI3 is predicted to be unstable with respect to NSCl -1-Cl2. ... 

Reaction of NSF3 with BCI3 yields the acyclic cation [N(SC1)2]" as its BCI4" salt (Fig. 15.48c) the compound is very hygroscopic and readily decomposes to BCI3, SCI2, S2CI2, and N2. 

As in the photolysis of protonated eucarvone, an acyclic intermediate is proposed in the mechanistic pathway. The protonated dienones 73 and 74 should be thermally stable, since a symmetry-allowed ring closure in the conrotatory mode is precluded in the cyclic system (Woodward and Hoffmann, 1970). Upon irradiation it can undergo a conrotatory ring opening however, to produce the acyclic cations 79 and 80 which in... 

Acyclic cationic systems, chalcogen-halogen compounds, 35 299-301 Acylarsonic acids, 44 217 Acyldiazenido complexes, mechanisms of formation, 27 223-225 Acylium cation, 9 231, 241-243 Acylphosphonic acids, 44 217 Acylsilane, hydrolysis, 42 173 Adamantane... 

Chalcogen dihalides, substituted, chalcogen(II) compounds, 35 278-279 Chalcogen-halogen compounds, 35 235-237 acyclic cationic systems, 35 299-301 cations containing homoatomic chalcogen rings, 35 295-298... 

Nesterenko and Staninets used quantum-chemical methods to examine the reaction of the phenylsulfenium ion (PhS ) with alkynes XCCY (X, Y = H, Me, Ph, CN) <2004TEC77>. Reaction was found to occur in two steps in general, forming first an acyclic cation 33 that could close to a thiirenium cation 34 or to a four-membered ring cation 35 (Scheme 4). The thiirenium ion 34 could rearrange to cation 35. All steps were described as reversible. 

Cobalt complexes of a-alkynylpyranosides undergo acid catalysed epimerisation by a mechanism involving an intermediate acyclic cation. The intermediate in this process may be trapped by nucleophiles to give derivatives which after suitable modification, may be induced to undergo thermodynamically controlled cyclisation to furnish dehydrooxepanes (Scheme 8) <94T12883>. Decomplexation may be readily carried out with iodine. 

With acyclic cations, once again the kinetic product is formed when the reaction is irreversible, while reversible processes result in a more thermodynamically stable product [Eqs. (189) (A. J. Birch and A. J. Pearson, unpublished work) and (190) (Maglio and Palumbo, 1974)]. 

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