Cyclopropanols structure

For most combinations of atoms, a number of molecular structures that differ fk m each other in the sequence of bonding of the atoms are possible. Each individual molecular assembly is called an isomer, and the constitution of a compound is the particular combination of bonds between atoms (molecular connectivity) which is characteristic of that structure. Propanal, allyl alcohol, acetone, 2-methyloxinine, and cyclopropanol each correspond to the molecular formula CjH O, but differ in constitution and are isomers of one another. 

Asymmetric cyclopropanol formation has been achieved with olefmic acylsulfonamides, which act like olefmic esters. Thus, their reaction with 1 provides a method for synthesizing cyclopropanols in an optically active form. As represented by Eq. 9.41, alkylation of Oppolzer s camphor sultam and reaction of the resulting unsaturated acylsulfonamides with 1 provides optically active bicyclic cyclopropanols having exclusively the structure shown in the equation [76],... 

A very useful class of chiral auxiliaries has been developed for alkenes substituted with a heteroatom. These auxiliaries, attached to the heteroatom, allow for the preparation of enantiomerically enriched cyclopropanols, cyclopropylamines and cyclopropylboronic acids. Tai and coworkers have developed a method to efficiently generate substituted cyclopropanol derivatives using the cyclopropanation of a chiral enol ether (equation 78) . The reaction proceeds with very high diastereocontrol with five- to eight-membered ring sizes as well as with acyclic enol ethers. The potential problem with the latter is the control of the double bond geometry upon enol ether formation. A detailed mechanistic study involving two zinc centers in the transition structure has been reported. ... 

A variety of three-membered carbocycles including cyclopropylcarbonyl and -sulfonyl derivatives, cyclopropylcarbonitriles and -methanols, nitrocyclopropanes, cyclopropanols and cyclopropylamines have been prepared via the 1,3-elimination of HX. Some representative cyclopropyl derivatives recently prepared by this method are shown in Scheme 1 and in equations 8-26. Conversion of chelated homoserine, 5,to chelated 2-amino-4-bromobutyrate and treatment with aqueous base directly affords chelated 1-aminocyclopropane-l-carboxylate (equation 8). The 1,3-elimination in 6 interestingly leads to the preferential formation of the cis isomer, from which 7, a key structural element of synthetic pyrethroid insecticides, is obtained (equation 9) . A sulfur substituent can serve both as an activating group and as a leaving group in this type of reaction and, thus, l,3-bis(phenylthio)propane affords cyclopropyl phenyl sulfide upon treatment with butyl-... 

Cyclopropanol may be regarded as the simplest homoenol, the cyclopropylalkoxide ion structure is one of the pair of hybrid structures which constitute the parent homoenolate ion (equation 14). 

More detailed isotopic labeling studies have also been performed. Hydroxycyclopropanation of trans-f.3-deutero-styrene 273 under Kulinkovich conditions furnishes m-2-phcny 1-1 -cyclopropanol, 274, indicating retention of configuration at the carbon bound to titanium and is consistent with frontside attack of the Ti-C bond on a titanium-bound carbonyl.220 For the related de Meijere cyclopropylamine synthesis, the opposite outcome has been observed where a 3 1 mixture of A, Wdimethyl-W(/ra t-3-deutero-/ra j-2-phenylcyclopropyl)amine 278 and -dim ethyl-. V-((7.i-dcutcro-t7r-2-phony Icyclopropy I )amine 277 is produced. These products require inversion of configuration at the carbon bound to titanium and are consistent with a W-shaped transition structure for ring closure (Scheme 46). 

Other Hydrogen Transfers - Weigel and Wagner S have studied the 1,4-hydrogen abstraction reactions within the ketones (37) leading to the cyclopropanols (38). The study used wavelengths > 300 nm with benzene or methanol as the solvents. The yields of products are shown below the structures. Polar solvents appeared to have no effect on the outcome of the reaction. 

With the exception of a few cyclopropanone hemiacetals, which are readily reduced with lithium aluminum hydride in diethyl ether to give the corresponding cyclopropanols, conversion of a cyclopropyl-oxygen bond to a cyclopropyl-hydrogen bond has only been achieved by reductive dealkoxylation of 1-alkoxycyclopropylamines where the alkoxy group is either methoxy or ethoxy 3. The reductions can be carried out with various hydrides, but the optimum reaction conditions in a specific case depend on the structure of the substrate. 

Alkyl-2-(phenylsulfonyl)cyclopropanols 5 were converted to the a,)S-unsaturated aldehydes 6 upon treatment with sodium hydrogen carbonate solution. The first step in this reaction could be either attack of hydroxide at the donor-substituted carbon or deprotonation of the homo-enol structure leading finally to elimination of the phenylsulfonyl group. 

Enolisation 1 involves the removal of the a-proton from a carbonyl compound to form an enolate ion 2. Homoenolisation involves the removal of a (i-proton 3 to form the homoenolate ion 4 or 5. Both the enolate and the homoenolate can be represented as carbanions, but whereas the enolate version 2b is merely a different way of representing a single delocalised structure, the homoenolate 5 is a different compound from the cyclopropane 4. No literal examples of homoenolates 5 are known so they have the status of synthons which may be represented in real life by reagents derived from cyclopropanols 4 among many other possibilities.1... 

These reactions are thought to involve oxidation of the agents, in the case of the hydrazines after initial oxidation to the diazenes, to free radicals that react with the heme group (Fig. 25). Explicit evidence exists for the isoporphyrin intermediate (bottom right structure. Fig. 25) in the case of cyclopropanol hydrate (Wiseman et al., 1982) and the alkylhydrazines (Ator et al., 1987, 1989). 

Cyclopropanols have been demonstrated to be ideal building blocks in the synthesis of structurally complex substances. The general scheme is the following ... 

More recently this form of cyclopropanol formation was found to occur with P-(p-aminophenyl)pro-piophenones, in which the aniline electron donor promotes a p-proton transfer and 1,3-biradical formation. - This study was particularly interesting in that phosphorescence of the intermediate exciplex was detected. Various structural modifications led to interesting diastereoselectivity in the products. 

The preparation and reactions of titanium-olefm complexes vith a nonmetallocene structure have also been kno vn since the pioneering vork of Kulinkovich et al. for the preparation of cyclopropanols, starting vith an ester, Ti(OPr-i)4 and an ethyl Grignard reagent (Scheme 12.36) [55[. The reaction involves dialkoxytitanacyclopropane as an actual reagent effecting the active transformation (Scheme 12.48). 

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