Neighboring hydroxyl group participation

Diethylaminosulfur trifluoride reacts with the 2-hydroxyl to form an intermediate (V) in which the neighboring benzyloxy group participates, forming a three-membered epoxide ring (VI). This is cleaved by the fluoride ion detached from the intermediate VI, and the result is a product with retention of configuration, benzyl 3-azido-4,6-0-benzylidene-2,3-dideoxy-2-fluoro-a-D-altropyranoside II. 

A1,2-0-isopropylidene acetal is formed in preference to a 1,2-carbonate. Where a primary alcohol group is present, preferential reaction with the pho ene occurs thereat, followed by cyclic carbonate formation (if participation with a neighboring hydroxyl group is sterically possible) the hydrogen chloride produced by these reactions catalyzes subsequent acetal formation at suitable positions. 

A neighboring hydroxyl group may participate in electrophilic addition reactions. Although this type of effect is discussed in more detail in Volume 2 some pertinent examples here will serve to illustrate this effect with alcohols. 

Ramachary, D. B., Madhavachary, R., Prasad, M. S. (2012). Observation of neighboring ortho-hydroxyl group participation in organocatalytic asymmetric sequential Michael-lactonization reactions synthesis of highly substituted chiral spirodihydro-coumarins. Organic Biomolecular Chemistry, 10, 5825-5829. 

Like the un-ionized hydroxyl group, an alkoxy group is a weak nucleophile. Nevertheless, it can operate as a neighboring nucleophile. For example, solvolysis of the isomeric p-bromobenzenesulfonate esters 6 and 7 leads to identical prxKluct nuxtures, suggesting the involvement of a common intermediate. This can be explained by involvement of the cyclic oxonium icai which would result from intramolecular participation. ... 

Somewhat milder oxidative conditions lead to loss of but one carbon. Periodic acid cleavage of the side chain in 65, leads to the so-called etio acid (66). Reaction with propionic anhydride leads to acylation of the 17-hydroxyl group (67). Possibilities for neighboring group participation severely limit the methods available for activating the acid for esterification. Best results seemed to have been obtained by use of a mixed anhydride from treatment with diphenyl chloro-... 

Stabilization of the carbonium ion can also be achieved by neighboring-group participation.91 This was probably the principal factor operative in the condensation of (3) to form a largely, possibly completely, jS-D-linked polymer1 (equation 7). Incidentally, if the conversion of (3) into (3a) occurred by protonation of the C-l hydroxyl group followed by... 

M. Miljkovic, D. Miljkovic, A. Jokic, V. Andrejevic, and E. A. Davidson, Neighboring group participation in carbohydrate chemistry. 3. Neighboring group participation of the 6-hydroxyl group in a nucleophilic displacement of a 5-p-toluenesulfonate, J. Org. Chem., 37 (1972) 2536-2540. 

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