Allylic rearrangements, transformation derivatives

The retrosynthesis involves the following transformations i) isomerisation of the endocyclic doble bond to the exo position ii) substitution of the terminal methylene group by a more stable carbonyl group (retro-Wittig reaction) iii) nucleophilic retro-Michael addition iv) reductive allylic rearrangement v) dealkylation of tertiary alcohol vi) homolytic cleavage and functionalisation vii) dehydroiodination viii) conversion of ethynyl ketone to carboxylic acid derivative ix) homolytic cleavage and functionalisation x) 3-bromo-debutylation xi) conversion of vinyl trimethylstannane to methyl 2-oxocyclopentanecarboxylate (67). 

Oxidation of the allylic carbon of alkenes may lead to allylic alcohols and derivatives or a, 3-unsaturated carbonyl compounds. Selenium dioxide is the reagent of choice to carry out the former transformation. In the latter process, which is more difficult to accomplish, Cr(VI) compounds are usually applied. In certain cases, mixture of products of both types of oxidation, as well as isomeric compounds resulting from allylic rearrangement, may be formed. Oxidation of 2-alkenes to the corresponding cc,p-unsaturated carboxylic acids, particularly the oxidation of propylene to acrolein and acrylic acid, as well as ammoxidation to acrylonitrile, has commercial importance (see Sections 9.5.2 and 9.5.3). 

Finally, let us consider the by-products of linalool transformation by I3 cinerea. The formation of 3,9-epoxy-p-menth-l-ene (27), the character impact compound of fresh dill herb (14), can be understood by allylic rearrangement of (E)-2,6-dimethyl-2,7-octadiene-1,6-diol (19) to the corresponding hydroxygeraniol (-nerol). This compound is known to undergo cyclization to the epoxy derivative (27) under acidic conditions (15). 

The cyanophosphates resulting from a,p-unsaturated ketones are readily transformed into conjugated allylic phosphate via a BF, FtiO-catalyzed allylic rearrangement (Scheme Similarly, the cyanophosphates derived from 1,4-benzoquinones react with aromatic and heteroaromatic compounds to give 3-aryl-4-hydroxybenzonitriles. ... 

Allylic rearrangement of thiocyanates to isothiocyanates has been demonstrated for monosaccharide derivatives, " - " opening up methods for sugar transformations but especially for s mthesizing amino-sugars. " For example, (165) gives (166) by way of the isothiocyanate resulting from thermal isomerization. " The allylic O-methanesulphonyl substituent in... 

A procedure for oxygen-nitrogen transposition with allylic rearrangement involves treating an allylic alcohol with trichloroacetonitrile, then heating the derived trichloroacetimidate. Rationalize this transformation. 

The data presented demonstrate that allylic sulfoxides can provide an easy and highly stereoselective route to allylic alcohols taking advantage of the facility of the allylic sulfoxide-sulfenate [2,3]-sigmatropic rearrangement. This is of considerable synthetic utility, since a number of stereoselective and useful transformations of allylic alcohols and their derivatives have become available in recent years107-109. 

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