Reaction at the Methyl Group

Oxidation of [1,3- C]acetone with selenium dioxide provided [1,3- C]methylglyoxal 12921 in 25 0% radiochemical yield . Aldol reaction with doubly deprotonated /3-keto acid 293 and simultaneous decarboxylation converted 292 to the 3-hydroxy-2,5-[l,3- ]diketone 294. This cyclized upon treatment with base to give doubly labeled aUethrolone 12951. the alcohol component of allethrine, a potent synthetic insecticide  

Though half of the label gets lost as p- Cjacetate when [1,3- C2]acetone is treated with iodine, this reaction is still a standard preparation procedure for [ C]iodoform. This compound is an indispensable precursor for [ C] methylene iodide , which is obtained by reduction of with sodium arsenite in alkaline medium. Diiodo[ C]methane in 

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Other authors241-245 observed that the relative rates of oxidation of alkylben-zenes by Co(III) acetate in acetic acid are the reverse of what would be expected for a classical free radical mechanism. For example, toluene is oxidized approximately 10 times as fast as cumene.241 242 245 Similarly, in the stoichiometric oxidation of p-cymene by Co(IIl) acetate in acetic acid,246 product formation occurred virtually exclusively via reaction at the methyl group to give p-iso-propylbenzyl acetate and p-isopropylbenzaldchyde ... 

A. The bridgehead methoxycarbonyl group is readily cleaved in a reaction, halolytlc fission, that is also an SN2 reaction at the methyl group. The other ester is more difficult to cleave, because access to the exo face of 50 is significantly more difficult on sleric grounds. Inspection of space-filling models shows this more clearly. 

Triazine 4-oxides with a methyl group in the 5- or 6-position react with ketene 0,iV-acetals to give [2-(dimethylamino)prop-l-enyl]-l,2,4-triazines 4-oxides 11 and 12 with a strong preference for reaction at the methyl group in the 5-position.145... 

Synthesis and polymerization of multifunctional cyclotriphosphazenes have been described <04PS%1>. A series of new nongeminal cyclophosphazenes 52 has been prepared via deprotonation-substitution reactions at the methyl groups of both cis and trans isomers of cyclotriphosphazene 51 with different electrophilic reagents <04PS817>. 

Poly(methylphenylphosphazene) can be derivatized through either deprotonation/substitution reactions at the methyl group or electrophilic aromatic substitution of the phenyl group. These reactions have been used to prepare a variety of new polyphosphazenes with all functional groups attached to the polymer backbone by direct P-C bonds. The synthesis and characterization of several of these new... 

Table II presents the originally obtained percent of reaction at the methyl group and corrected relative rates of hydrogen abstraction. Also shown are the calculated relative energy differences between the arylmethyl radical and the initial arene. It can be seen that a large range of experimental reactivities, nearly three powers of ten, is encountered.

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