Cyclopropyl Carbinols Research Articles

Synthesis of β‐Peroxy‐Lactones Using 30% H2O2.

AbstractFor Abstract see ChemInform Abstract in Full Text.

An Effective and Highly Stereoselective Julia Olefination of Cyclopropyl Carbinol Mediated by CeCl3·7H2O/NaI

[reaction: see text] An efficient and highly stereoselective synthesis of functionalized trisubstituted E-olefins from cyclopropyl carbinol derivatives via a Julia-type olefination mediated by an intriguing Lewis acidic system consisting of CeCl(3).7H(2)O and NaI in refluxing acetonitrile is reported. This facile olefination allows for the iterative incorporation of methylcyclopropyl ketone as a C(5) prenylation synthon in the synthesis of acyclic terpenoids, as demonstrated in the facile synthesis of plaunotol 6E-isomer 12, a biologically significant diterpene diol, and naturally occurring diterpene 17.

Synthesis of β-peroxy-lactones using 30% H 2O 2

Cyclopropyl carbinols 1a– e react with H 2O 2 in the presence of concd H 2SO 4 at 0–5 °C to furnish the corresponding hydroperoxides 2a– e in 45–82% yields. This efficient trapping of cyclopropylmethyl cations by the hydroperoxy group has been exploited to prepare compounds 14– 23 , a new series of cyclopropyl substituted β-peroxy-lactones.

Heavy atom structure and conformer stabilities of cyclopropyl carbinol from rotational spectroscopy and ab initio calculations

A remeasurement of the rotational spectra of the normal and hydroxyl deuterated isotopomers of cyclopropyl carbinol (cyclopropane methanol, (CH 2) 2CH(CH 2OH)) using Fourier-transform microwave spectroscopy has provided refined rotational constants and centrifugal distortion constants for this molecule. Rotational constants for an additional four singly substituted 13C isotopomers, the OD isotopomer, and the 18O isotopomer are consistent with a conformer in which the OH group forms an intramolecular hydrogen bond with the edge of the cyclopropyl ring. The observed a-type transition frequencies for the normal and deuterated species are in reasonable agreement with a previous microwave study (although some frequencies differ by several hundred kilohertz), but the few b- and c-type lines that were measured in the range of our spectrometer were found to differ by several megahertz from the previous literature measurements, leading to A rotational constants that differ significantly from those reported previously. The refined rotational constants for the normal isotopic species are A=12470.7795(23) MHz, B=3236.4678(7) MHz, C=2894.4831(7) MHz, while those of the deuterated species are A=12069.2653(24) MHz, B=3177.1540(8) MHz and C=2826.2658(7) MHz. Results of ab initio optimizations on seven conformers for this molecule carried out at the MP2/6-311+G(d,p) level will be compared with the experimentally determined structural parameters.

Highly Stereoselective Prins Cyclization of Silylmethyl‐Substituted Cyclopropyl Carbinols to 2,4,6‐Trisubstituted Tetrahydropyrans.

The homoallyl cation formed from a cyclopropyl carbinol that was vicinally substituted by a silylmethyl function underwent smooth Prins cyclization with aldehydes and ketones to form 2,4,6-trisubstituted tetrahydropyrans with very high stereoselectivity.

A Novel Synthesis of Functionalized Allylsilanes

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Highly stereoselective prins cyclization of silylmethyl-substituted cyclopropyl carbinols to 2,4,6-trisubstituted tetrahydropyrans.

The homoallyl cation formed from a cyclopropyl carbinol that was vicinally substituted by a silylmethyl function underwent smooth Prins cyclization with aldehydes and ketones to form 2,4,6-trisubstituted tetrahydropyrans with very high stereoselectivity.

A novel synthesis of functionalized allylsilanes.

A novel facile synthesis of substituted and functionalized allylsilane has been developed. This essentially one-pot procedure involves (1) (dimethylphenylsilyl)methyl cerium chloride addition to cyclopropyl ketone and (2) MgI(2) etherate-mediated Julia homoallylic transposition of the corresponding cyclopropyl carbinol. The bifunctional homoiodo allylsilanes, readily accessible by this method, would be useful and versatile synthons in organic synthesis. [reaction: see text]

Cyclopropane Structural Units from Homoaldol Adducts.

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LiBF 4: a mild and novel reagent for the OH insertion reactions of α-diazoketones

Lithium tetrafluoroborate (10 mol%) is found to catalyze efficiently the OH insertion reactions of α-diazoketones with various alcohols including benzylic, allylic, propargylic and cyclopropyl carbinols to produce the corresponding α-alkoxy ketones in excellent yields with high selectivity. A solution of 10 mol% of LiBF 4 in acetonitrile provides a convenient reaction medium to carry out the OH insertion reactions under mild and neutral conditions.

Cyclopropane structural units from homoaldol adducts.

[reaction: see text] An efficient two-step homologation of aldehydes to cyclopropylaldehydes has been developed. Activation of homoaldol adducts derived from O-enecarbamates and N-enecarbamates provided high yields of cyclopropylaldehydes with good to excellent levels of trans/cis selectivity. Trapping of the intermediate oxonium ion and iminium ion intermediates has also been demonstrated, leading to direct isolation of cyclopropyl carbinol and cyclopropylamine products.

ChemInform Abstract: Synthesis of γ‐Methylene Oxacycles and α‐ and β‐Alkylidene Lactones via Silicon‐Assisted Ring Opening of Cyclopropyl Carbinols.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Synthesis of gamma-methylene oxacycles and alpha- and beta-alkylidene lactones via silicon-assisted ring opening of cyclopropyl carbinols.

Cyclopropyl carbinols bearing a (tert-butyldiphenylsilyl)methyl substituent undergo silicon-assisted regioselective ring cleavage and the resulting beta-silyl carbocation is intramolecularly trapped with hydroxy and ester functions to generate gamma-methylene oxacycles and alpha- and beta-alkylidene lactones without the cleavage of the silicon function.

Use of metallated allylic ethers for the elaboration of vicinally trisubstituted linear substrates or cyclopropyl carbinols

Allyl zinc reagents derived from allylic ethers carbometallate vinyllithiums derived from secondary allylic ethers, leading to linear 3,5-dialkoxy-4-methyl-1-alkenes, or to 1-vinyl-2-alkoxyalkyl cyclopropanes diastereoselectively.

A new approach to the synthesis of a polyfunctional acyclic chiral building block based on ethyl ( S)-(–)-lactate

Based on ethyl (S)-(–)-lactate, an original sequence of highly stereoselective transformations leading to (4S,5E)-4-bromomethylhept-5-enenitrile was developed using rearrangement of a chiral cyclopropyl carbinol as the key step.

ChemInform Abstract: Formation of Cyclopropyl Carbinols Through a Highly Diastereoselective Hydrozirconation of Vinyloxirane Derivatives.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Formation of cyclopropyl carbinols through a highly diastereoselective hydrozirconation of vinyloxirane derivatives

Cyclopropyl carbinol derivatives were efficiently prepared through a highly diastereoselective hydrozirconation of vinyloxirones and the intramolecular nucleophilic attack of the generated alkylzirconocene with the inversion of the configuration at the reacting oxirane carbon.

ChemInform Abstract: Diastereoselectivity in the Cyclopropanation of 3,3‐Bimetallic Allylic Alcohols. Preparation of Diastereomeric Cyclopropyl Carbinols via a Simple Oxidation‐Reduction Sequence.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Diastereoselectivity in the Cyclopropanation of 3,3-Bimetallic Allylic Alcohols. Preparation of Diastereomeric Cyclopropyl Carbinols via a Simple Oxidation-Reduction Sequence

Diastereoselectivity in the Cyclopropanation of 3,3-Bimetallic Allylic Alcohols. Preparation of Diastereomeric Cyclopropyl Carbinols via a Simple Oxidation-Reduction Sequence

Rearrangement studies on 3,3-bis(methylthio)-1-(arylcyclopropyl) -2-propen-1-ols: Synthesis of functionalized cyclopentenes and polyene esters

The cyclopropyl carbinols 8 and 9 obtained by either borohydride reduction (or Grignard addition) of the cyclopropyl ketones 1 are shown to undergo acid induced ring opening and intramolecular cyclization (5-exo or 6-endo) or deprotonation to afford either cyclopentene, biphenyl or conjugated polyene derivatives depending on the nature of Lewis acid, reaction conditions and the structuralfeatures present in the cyclopropyl carbinol. A probable mechanism for the formation of various products has been suggested.