2-Methyltetrahydrofuran acetonitrile

In contrast to the preceding atom-transfer reaction, the solvent-induced rate change for the reaction between l-ethyl-4-(methoxycarbonyl)pyridinyl and 4-(halomethyl)-nitrobenzenes is so large that a change in mechanism must be involved [215, 570]. In changing the solvent from 2-methyltetrahydrofuran to acetonitrile, the relative rate constant for 4-(bromomethyl)-nitrobenzene increases by a factor of up to 14800. This is of the order expected for a reaction in which an ion pair is created from a pair of neutral molecules [cf. for example, reaction (5-16)]. It has been confirmed therefore that, according to scheme (5-67), an electron-transfer process is involved [215, 570]. 

The rate constants for the reaction of a series of benzyl halides with 4 (Table 4) revealed that the rate for the 4-nitrobenzyl chloride was extraordinarily high, being millions of times faster than expected . A change of mechanism was suspected solvent polarity changes affected the rate constants very much, viHith the rate changing by a factor of 10 from 2-methyltetrahydrofuran (Z 55.4) to acetonitrile (Z 71.3)... 

IO = isooctane H = hexane MTHF = 2-methyltetrahydrofuran A = acetonitrile T = toluene MC = methylene chloride E = ethanol. 

Methyltetrahydrofuran allowed to react 12hrs. at 25° with acetyl tosylate -> 1-acetoxypentyl 4-p-tosylate. Y 95%. - Catalysis by added Lewis acids is not necessary and cleavage of the most unreactive ethers occurs after a few hrs. reflux in acetonitrile. The cleavage of unsym. ethers favors a greater specificity than other methods. M. H. Karger and Y. Mazur, Am. Soc. 90, 3878 (1968). 

Abbreviations Agg. = aggregates AcrCN = acrylonitrile DMF = V,V-dimethylformamide DMSO = dimeth-ylsulfoxide EC = ethylene carbonate HC02Et = ethyl formate Me2CO = acetone MeCN = acetonitrile MeCOsMe = methyl acetate MeTHF = 2-methyltetrahydrofuran PC = propylene carbonate THF = tetrahy-drofuran THP = tetrahydropyran. 

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