Methyl iodide, reaction

The KIE in the 2,6-dimethylpyridine-methyl iodide reaction is more than twice the KIE in the 2-methylpyridine-methyl iodide reaction. This is also consistent with a steric origin for the KIE because the 2,6-dimethylpyridine transition state must be much more sterically crowded than the 2-methyl-pyridine transition state. If the increase had been due to an inductive effect, the increase in the KIE in the 2,6-dimethylpyridine reaction should have been approximately twice the KIE for the 2-methylpyridine reaction, i.e. approximately 0.94 rather than the 0.91 that was observed. 

The steric rather than the inductive origin of the secondary deuterium KIE is also suggested because kH/kD = 0.994 per deuterium found in the per-deuteropyridine-methyl iodide reaction is smaller (less inverse) than the kH/kn = 0.988 per deuterium found for the 4-deuteropyridine reaction. A secondary inductive KIE should be more inverse when a deuterium is substituted for a hydrogen nearer the reaction centre, i.e. at the meta- or ortho-rather than at the para-position of the pyridine ring. Thus, if the KIE were inductive in origin, the KIE in the perdeuteropyridine reaction should be more inverse than that observed for the 4-deuteropyridine reaction. If the observed KIE were the result of a steric KIE, on the other hand, a less inverse KIE per deuterium could be found in the perdeuteropyridine reaction, i.e. a less inverse KIE per deuterium would be expected if there were little or no increase in steric hindrance around the C—H(D) bonds as the substrate was converted into the SN2 transition state. Since the KIE per D for the perdeuteropyridine reaction is less than 1%, the transition state must not be sterically crowded and the KIE must be steric in origin. Finally, the secondary deuterium KIEs observed in the reactions between 2-methyl-d3-pyridine and methyl-, ethyl- and isopropyl iodides (entries 3, 7 and 9, Table 17) are not consistent with an inductive KIE. If an inductive KIE were important in these reactions, one would expect the same KIE for all three reactions because the deuteriums would increase the nucleophilicity of the pyridine by the same amount in each reaction. The different KIEs for these three reactions are consistent with a steric KIE because the most inverse KIE is observed in the isopropyl iodide reaction, which would be expected to have the most crowded transition state, and the least inverse KIE is found in the methyl iodide reaction, where the transition state is the least crowded. 

Large (near the theoretical maximum) a-carbon KIEs for the Menshutkin reactions between 3,5-disubstituted pyridines and methyl iodide [reaction (22) Table 20] have also been reported by Yamataka and co-workers (Ando et al., 1987). Although the a-carbon KIEs increase slightly as more electron-withdrawing substituents are added to the nucleophile, they are all large and... 

Product elucidation of trimethyloxonium tetrafluoroborate and methyl iodide reactions with [l,2,3]triazolo[4,5- -pyridazines (Schemes 1-3) using mainly 2-D heteronuclear multiple bond correlation (HMBC). NMR... 

The synthesis of yet another example begins with the allylation of the enamide (21-2) with methyl iodide. Reaction of this intermediate (23-1) as above with the ami-nopyrrazole (23-2) leads to the formation of the fused pyrimidinopyrrazole (23-3). This last productis is next acylated with thiazole-carboxillic acid (23-4) in the presence of aluminum chloride. There is thus obtained the sleep inducing agent indiplon (23-5) [24]. 

Methyl iodide, reactions with dialkyl-amino-thiazoles, 32. See also Alkylation 4-Methylthiazole, preparation of, from Na/NH3 reduction of 4-methyl-A-4-thiazoline-2-thione, 397 2-Methylthio-3-methylthiazolium salts, as catalyst for methylthiothiazole rearrangement, 406 Methylvinylketone, reaction of, with... 

The monobenzo compound (107 R1=R2 = H) forms a stable salt with methyl iodide. Reaction with TCNE results in elimination of hydrogen cyanide and formation of the tricyanovinyl derivative (107 R1 = C(CN)=C(CN)2, R2 = H) (67JA2626). 

Since the reaction of nucleophiles with methyl iodide can be measured much more easily and accurately by spectroscopic analysis of the product iodide ion, a subsequent set of n values was devised using Equation (44). The n value of methanol with methyl iodide is set at zero and the reaction constant, s, at unity. Values of n derived from the methyl iodide reaction are tabulated in Appendix 3, Table 5. 

The rates of these reactions are strongly influenced by the nature of the halide ligand X and the solvent. For example, the rate at which methyl iodide adds to (III) follows the order Cl > Br > I. The reaction with methyl iodide is much faster in dimethylformamide than in benzene. For example, the rate of methyl iodide addition to the chloride complex at 30° C in dimethylformamide is nearly 17 times faster than the same reaction in benzene. The activation parameters for the methyl iodide reactions are in the range dH = 5.6 to 8.8 kcal/mole and 43 to —51 e.u., and reveal a... 

Tetrabutylammonium tetrahydridoborate methyl iodide Reactions with dihorane in methylene chloride Prim, amines from nitriles... 

Bunker DL, Goring-Simpson E (1973) Alkali-methyl iodide reactions. Faraday Discuss Chem Soc 55 93... 

The synthetic access to a broad variety of nucleophilic [ C]methyl and [ " C]methylene synthons has significantly widened the scope of [ C]methyl iodide. Reaction with... 

D. L, Bunker and E. A. Goring-Simpson, Alkali-methyl iodide reactions, Faraday Disc. Chem. Soc. 55 93 (1973). 

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