Readily available sulphonates of tertiary cyclopropanols are converted into 2-substituted allyl bromides in high yields under the action of magnesium bromide in diethyl ether. Magnesium chloride, aluminium chloride and titanium tetrachloride also induce effectively the transformation of cyclopropyl sulphonates into the corresponding allyl chlorides.Tertiary cyclopropanols are readily available by the cyclopropanation of esters, 1,2 desilylation of cyclopropanol silyl ethers, 3,4 alkylation of cyclopropanone hemiacetals, 5,6 and using some other approaches. 7 Their synthetic applications are based mainly on the ring opening reactions, when one of the bonds adjacent to carbinol carbon atom (C1-C2 or C1-C3 bonds in cyclopropane ring) undergoes cleavage. These transformations are usually initiated with electrophilic, basic or oxidizing reagents 4,6-8 and strongly facilitated by electron-donating oxygen atom. In contrast, solvolysis of cyclopropyl p-toluenesulphonates and triflates is usually accompanied by the C2-C3 cyclopropane ring cleavage, and these reactions were intensively studied stereochemically and kinetically with a mechanistic interest to the cationic cyclopropyl-allyl rearrangement. 7,9-11 Nevertheless, the preparative value of this transformation was not demonstrated clearly. We now report a simple and highly efficient procedure for the conversion of cyclopropyl sulphonates into 2-substituted allyl halides, which are widely used in organic synthesis, and believe that this finding will contribute to reducing the disbalance in synthetic application of C1-C2 versus C2-C3 modes of the cyclopropanol ring opening reactions.

The preparation of functionalized 2-substituted allyl bromides and chlorides from carboxylic esters is reported. The carboxylic esters were transformed first to 1-substituted cyclopropanols by treating with ethylmagnesium bromide in the presence of titanium alkoxide. Mesylation of the cyclopropanols followed by halide displacement of the sulfonate group to halogen, accompanied by cyclopropyl-allyl rearrangement, affords the required allyl bromides and chlorides.

Separation of optical isomers obtainable from trans-norborn-5-ene-2,3-dicarboxylic acid methyl and tert-butyl monoesters was performed by crystallization of the respective salts prepared with (R)- and (S)-1-phenylethylamine. Starting from racemic endo-monomethyl ester of trans-norborn-5-ene-2,3-dicarboxylic acid, prepared by partial hydrolysis of the cyclopentadiene-dimethyl fumarate adduct, the corresponding (2R,3R)-endo-monoester was isolated in 97% enantiomeric excess (ee) yield after seven repeated crystallizations from tetrachloromethane. Starting from exo-mono-tert-butyl ester of the same acid, prepared by alcoholysis of the cyclopentadiene-maleic anhydride adduct followed by isomerization, (2R,3R)-exo-monoester was isolated in >98% ee yield after four repeated crystallizations from ethanol. Crystallization of the acids from the mother liquor containing (S)-1-phenylethylamine yielded products with inverse stereochemical configuration.

Spirocyclic sulfates of 2-and 3-(hydroxyalkyl)cyclopropanols, obtainable through the Kulinkovich reaction from β-and γhydroxy carboxylic acid esters, respectively, were synthesized for the first time. The possibility of regio-and stereoselective alkylating the spirocyclic sulfates by using Normant homocuprates has been demonstrated.

Methyl ketones or ethyl acetate react with aromatic abromo ketones in the presence of two equivalents of tert-butoxyor diethylaminomagnesium bromide in benzene (toluene) under reflux to produce 1-aryl-2,4-diones. The conversion, apparently, occurs via aldol condensation and subsequent [1,2]-sigmatropic rearrangement of the intermediate 3-bromo-2-hydroxy ketones. A number of fused aromatic and heteroaromatic phenols have been prepared by cyclodehydration of 1-aryl-2,4-diones.