Nucleophiles intramolecular hydrogen bonding

C NMR, 6, 398 molecular dimensions, 6, 397 tautomerism, 6, 404 Furoxan-3-carbohydra2ide intramolecular hydrogen bonding, 6, 396 Furoxan-3-carboxamide intramolecular hydrogen bonding, 6, 396 Furoxancarboxylic acids reactions, 6, 413 with nucleophiles, 6, 406 Furoxan-3,4-dicarbaldoxime synthesis, 6, 409 Furoxanoaaines fused... 

Several cyclopropylimines have been synthesized and their reactions with a range of nucleophiles have been investigated. Mild hydrolysis of diimine (16) produces, amongst other products, the /3-ketoimine (17), stabilized by intramolecular hydrogen bonding. 

A kinetic smdy has been reported of substituent effects on the reactions of 2-phenoxy- and 2-(4-nitrophenoxy)-3-nitro-5-X-thiophenes with benzylamine and with A-methylbenzylamine in benzene as solvent. The intramolecularly hydrogen-bonded intermediate (14) is postulated. Reactions of the 5-unsubstimted thiophenes (X = H) are not base-catalysed, indicating that nucleophilic attack is rate limiting, and the more basic secondary amine shows higher reactivity than the primary... 

Intramolecular hydrogen bonding has been proposed to facilitate nucleophilic addition of sulfones to the Morita-Baylis-Hillman adducts in a single step to produce the substituted allyl sulfones.178... 

Such behavior of amine 213 in [202] was explained by the presence of an intramolecular hydrogen bond and the electron-withdrawing influence of the carboxamide moiety on the nucleophilicity of the amino group. Owing to the formation of intermediates E and F, the reaction products of the multicomponent and sequential processes are identical. 

The rate and the conversion of the Baylis-Hillman-reaction was significantly improved when nucleophilic non-hindered bases, such as diaza[2.2.2]bicyclooctane (DABCO, 6), rather than simple tertiary amines were used. Further improvements were observed when 3-quinuclidinole (3-QDL, 7) was employed, due to stabilization of the zwitterionic intermediate 2 by formation of intramolecular hydrogen bonds [14a-c]. Similar effects were observed by the addition of methanol [14d] or acetic acid [14e] to the reaction mixture (formation of intermolecular hydrogen bonds) or by the presence of a hydroxy group in the acrylate [14f ]. The rate of the reaction was decreased by the presence of substituents in the a-position of tertiary amines. This was explained by the decrease of the rate of the addition of the catalyst onto the acrylate [15]. 

It is likely that the phenolic hydroxyl of 1 is much less nucleophilic than the allylic OH because of its involvement in strong intramolecular hydrogen bonding with the ortho carbonyl of the ester. This would... 

This is probably because intramolecular hydrogen bonding with the phenolic hydroxyl in the 1 1 adduct reduces the nucleophilic character of the amine nitrogen sufficiently to render it unreactive in a second step. 

The product aldehyde is not at risk from nucleophilic attack, as it appears to be, because it immediately enolizes in base. The product is formed as a stable enol with an intramolecular hydrogen bond. 

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