Stability methoxymethyl cation

The methoxymethyl cation can be obtained as a stable solid, MeOCH SbF Carbocations containing either a, p, or y silicon atom are also stabilized, relative to similar ions without the silicon atom. 

The stability of the carbocation is also increased due to the presence of heteroatom having an unshared pair of electrons, e.g. oxygen, nitrogen or halogen, adjacent to the cationic centre. Such carbocations are stabilized by resonance. The methoxymethyl cation is obtained as a stable solid, MeOCH2 SbF4. ... 

The methoxymethyl cation can be obtained as a stable sohd, MeOCHj SbF, Carbocations containing either a, p, or y silicon atom are also stabilized, relative to similar ions without the silicon atom. In super acid solution, ions such as CX (X = Cl, Br, I) have been prepared. Vinyl-stabilized halonium ions are also known. ... 

Relatively stabilized carbocations can be used to alkylate the pyrrole and indole rings. Introduction of formyl groups, for example, can be done with MeOCHCl2, via a reaction which likely proceeds through the 1-chloro-l-methoxymethyl cation, (Scheme 94) <72JMC97, 86SC1799). 

Examples of two primary carbonium ions stabilized by electron-releasing substituents are included in entries 5 and 13. Both the methoxymethyl cation and... 

Ion cyclotron resonance studies of 3-methoxyalkanethiols and homologous sulphides MeO(CH2) SMe (n = 1—3/ have provided information on the reactivity profile of the methoxymethyl cation towards alcohols, thiols, and amines, and on the preferential abstraction of hydride ion from the carbon atoms that are alpha to sulphur (confirming that, in gas-phase reactions, S is more able than O to stabilize a neighbouring carbonium ion). Gas-phase acidities of dimethyl sulphoxide and representative aliphatic sulphones reveal a lower degree of stabilization of the cr-sulphonyl carbonium ions. ... 

Bulky groups such as methoxymethyl (which is also inductively destabilizing to a cation) resulted in mixtures of the two regioisomeric products from cyclization at the substituted and unsubstituted position. When the a substituent R is an aryl group such as p-tolyl, despite its cation-stabilizing properties, the regio- and stereocontrol of the reaction is lost due to its bulk thus three isomers 67,68, and 69, of the tricyclic product were isolated. While the first step of the cyclization process, the H abstraction, has been... 

Like organosilyl cations stabilized by two 2-(methoxymethyl)phenyl ligands [4], 11 reacts with pyridine with transfer of a methyl group and formation of a cyclic silyl ether 17. In contrast to organosilyl cations chelated by two 2-(methylthiomethyl)phenyl ligands, a displacement of the intramolecular donors by pyridine is not possible in 12 (Scheme 3). 

---