Cyclopropanols have been principally synthesized by (1) reaction of epichlorohydrins with magnesium bromide followed by treatment with Grignard reagent and ferric chloride, (2) acid hydrolysis of cyclopropyl vinyl ethers, and (3) hydrolysis of cyclopropyl acetates which are available via the Baeyer-Villiger oxidation of methyl cyclopropyl ketones or pyrolysis of acetoxypyrazolines. Cleavage of a carbon-carbon bond of cyclopropanols or cyclopropyl acetates occurs upon reaction with electrophiles, leading to incorporation of the electrophile in the C2 (or C3) position of the original cyclopropane in the final product. Protonic acids attack trans-2-phenyl-l-methylcyclopropanol leading to retention of configuration in the product. Reaction of this same alcohol with electrophilic halogen (t-butyl hypohalite, N-bromosuccinimide) gives inversion of configuration. When trans,trans- or cis,trans-2,3-dimethyl-l-phenylcyclopropanol is cleaved with brominating agents, bromoketones are formed, also with inversion of configuration. In base-catalyzed cleavage of cyclopropanols, protonation occurs with inversion of configuration. Solvolysis of cyclopropyl tosylates and halides generally occurs with simultaneous ring opening and with the ultimate formation of allyl cations. The Woodward-Hoffmann rules, which predict a disrotatory mode of opening, are obeyed. In addition, a selection between the two allowed disrotatory modes is imposed by the relative configurational geometry of the leaving group; groups trans to the leaving group rotate outwardly and groups cis rotate inwardly. Nitrite esters of cyclopropanols rearrange spontaneously to nitroso ketones. Cyclopropanols are easily oxidized with ferric chloride, implying that homolytic cleavage of the O-X bond is exceptionally easy. Cyclopropyl acetates generally rearrange upon pyrolysis and form allyl acetates. © 1968, American Chemical Society. All rights reserved.
