Oxonium salts, cleavage

A closely related reaction is cleavage of oxonium salts. 

Reaction of halides with oxide ion 0-68 Cleavage of oxonium salts 0-79 Reduction of acetals or ketals 0-92 Reaction between Grignard reagents and acetals or ketals dimerization of acetals... 

Formation of the inner oxonium salt may he preceded by an intermediate oxonium state (Eq. 953) of the type considered above Cleavage of the oxonium ling is then accomplished by nucleophilic... 

The surprising stability of triaryloxonium ions has been demonstrated by the fact that reduction of the tris(4-nitrophenyl)oxonium tetrafluoroborate 35 can be performed to give the tris(4-aminophenyl)oxonium salt 36 without cleavage of aryl oxygen bonds [Eq. (4.21)]. Diazotation of this amino derivative and reaction with iodide leads to the tris(/v/ra-iodophenyl)oxonium salt 37 in excellent yields.104... 

Quantum mechanical calculations show that the silyl cation (19) has a twisted structure, and that the a-C02 group provides substantial electrostatic stabilization.58 Isotope effects for its formation reaction are also reported.58 Evidence is provided for the stabilization of incipient oxocarbenium ions by axial electronegative substituents, as in (20) the presence of the most electronegative substituent results in the fastest reaction.59 Lewis acid-promoted cleavage of spirocyclic dioxanes such as (21) involves oxonium ions, and high axial vs equatorial product selectivities are possible with the correct choice of Lewis acid and nucleophile.60 Reactions which lead to 1,3-dioxenium salts have been reviewed.61... 

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