Alkoxy leaving groups

By determining ha for several different buffer catalysts and each of several alkoxy leaving groups, it was determined that there was a relationship between the Bronsted eoeffieient a and the strueture of the alkoxy leaving group. The data are given and show that a deereases as the alkoxy group beeomes less basie. 

An important example of indirect substitution utilizes alkoxy leaving groups the intermediate (28) from the reaction of the [(diphenyl ether)Cr(CO)3] complex and the 2-methyl-1,3-dithiane anion can be induced to eliminate phenol by protonation at low temperature the result is tele substitution (equation 17). 

Contrary to the oxonium intermediate 115 (Section III,C,2), the intermediate 211 having the alkoxy leaving group readily opens its heterocyclic ring under these conditions. Diketones 205 (R3 is not H) thus formed are then cyclized into a-naphthols 204 (or /3-naphthols of type 209). If anhydro-bases 212 were formed, they would have to take part in the analogous conversions described previously. Obviously, the same mechanism may be applied to the scheme of formation of a-naphthols 204 from 2-benzopyrylium salts under the action of dimethylamine hydrochloride in ethanol (77KGS996) (cf. Section III,C,4,a,iv). 

A mixture of o-hydrazinobenzoic acid hydrodiloride, ethyl 2-cyano-3-ethoxy-acrylate, ethanol, and water heated 10 min. on a steam bath, and allowed to stand overnight at room temp. ethyl pyrazolo[l,5-a]quinazolin-5(4H)-one-3-carboxylate. Y 85%. F. e., also with amino and cyano in place of alkoxy leaving groups, s. J. B. Wright, J. Heterocyclic Chem. 6, 947 (1969). 

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