Ring contraction alcohols, cyclic

The procedure described is essentially that of Shioiri and Yamada. Diphenyl phosphorazidate is a useful and versatile reagent in organic synthesis. It has been used for racemlzatlon-free peptide syntheses, thiol ester synthesis, a modified Curtius reaction, an esterification of a-substituted carboxylic acld, formation of diketoplperazines, alkyl azide synthesis, phosphorylation of alcohols and amines,and polymerization of amino acids and peptides. - Furthermore, diphenyl phosphorazidate acts as a nitrene source and as a 1,3-dipole.An example in the ring contraction of cyclic ketones to form cycloalkanecarboxylic acids is presented in the next procedure, this volume. 

In view of the analogous behavior of 1,3-cyclooctadiene monoepoxide (52), it appears that the double bond in this molecule has little effect on the course of the reaction.88 When the tram epoxide 53 is involved, the hydroxyl group in the bi-cyclic alcohol is oriented exo and a reasonable amount of ring contracted aldehyde can be isolated.87 ... 

To emphasise the importance of this ring contraction during the course of substitution reactions at C-2 discussed above, an example with preparative attraction [52] is outlined in Scheme 13 (the transformation is also operative with the a-anomer). Here advantage is taken of the (regular) ring contraction of - mono-cyclic - glucopyranosides under solvolytic conditions, after they had been used as chiral auxiliaries in the asymmetric cyclopropanylation of allyl alcohols. 

Carvone-derived 2,3-epoxy alcohol derivatives (317) have been found to rearrange with stereoselective formation of ring-contracted ketones (318) in a process where the stereochemical result seems to be independent of epoxide configuration. On the basis of this study, the authors concluded that the rearrangement of tetrasubstituted cyclic epoxy alcohol derivatives remains a transformation for which both regiose-lectivity and stereochemical outcome are difficult to predict. New solid acid catalysts based on silica-supported zinc triflate have been prepared for use in the rearrangement of a-pinene oxide to campholenic aldehyde. ... 

Rearrangement of (3-amino alcohols upon diazotization with nitrous acid to give carbonyl compounds. Cyclic alcohols yield ring expanded or contracted products ... 

---