Cyclopropylmethyl acetate

Using an alternative method, homoallylic iodides are efficiently transformed into cyclopropylmethyl acetates using silver acetate in anhydrous benzene (Table 1). y-Disubstituted or conjugated homoallylic iodides are particularly reactive and rearrange quantitatively. y-Monosub-stituted iodides afford mixtures of cyclopropylmethyl and homoallyl acetates in a 1 1 ratio, whereas the absence of a y-alkyl or aryl group in the homoallylic iodides leads to elimination, only. 

Acetolysis of 3-(4-bromophenylsulfonyloxy)-3,4,7,8-2//-oxocine gives a mixture of acetates 1-4 in 97% yield. The epimeric cyclopropylmethyl acetates 3 and 4 were isolated in 22 and 69% yield, respectively, by preparative gas chromatography. A similar reaction pattern has previously been reported for cyclooctenyl derivatives. ... 

Strain energy of the bridgehead alkenes. A decrease in ring size favors the formation of the cyclopropylmethyl acetates. 

A cyclopropylacetic acid moiety was converted to a cyclopropylmethyl acetate by electrochemical oxidation in the presence of acetic acid ° or by treatment with lead(lV) acetate in the presence of pyridine. When the reaction was performed in the presence of methanol instead... 

A large number of cyclopropylmethyl acetals have been converted to the corresponding carbonyl compounds by hydrolysis. The yields were generally good to excellent, but severe byproduct formation has been reported.Usually, a mineral acid, such as hydrochloric acid, sulfuric acid, and perchloric acid,2 2 3,357,392,407.449,450,477,483.511, 573,721,726,745,767,1012,1061,1410,1413.1415-1429 catalyst, but Ambcrlite, formic p-toluenesulfonic pyridinium... 

Bei der Hydrolyse von (136) und (137) entsteht neben der entsprechenden Vierringverbindung hauptsachlich Spiroalkohol, was auf die unverminderte Stabilitat der Cyclopropylmethyl-Kationen hinweist. Entsprechend zeigt das nach Crrob (169) fast ideal konfigurierte (138) ein UV-Maximum hoher Extinktion bei 213 mg (720). Die epimeren p-Nitrobenzoate bzw. Acetate... 

No reactions of t with protic solvents have been reported however, its cyclic analogue 1,2-diphenylcyclobutene (7) reacts with the protic solvents methanol, acetic acid, and water, to yield adducts 85 and 86 (eq. 28). The proposed mechanism for the formation of 85 and 86 involves the formation of singlet exciplex followed by proton transfer to yield a cyclobutyl cation 87. Stereoselective nucleophilic capture of 87 by solvent from its less hindered side yields 85, while skeletal rearrangement of 87 yields the cyclopropylmethyl cation 88, which reacts with solvent to yield 86 ... 

A solution of 17-cyclopropylmethylnorcodeinone dienol acetate (1.00 g, 2.63 mmol), formic acid (8 ml, 90%), and hydrogen peroxide (0.37 g, 30%, 3.26 mmol) was heated at 44°-45°C for 6 hr, added water (20 ml) and ethyl acetate (80 ml), basified with sodium bicarbonate. The organic portion was separated, washed with water (15 ml), dried over anhydrous sodium sulfate and evaporated in vacuo to dryness, the residue (0.9 g) was chromatographed on silica gel with methanol/methylene chloride (2.5/97.5) to give 17-cyclopropylmethyl-14-hydroxynorcodeinone (0.72 g, 78% yield). 

A mixture of cyclopropylmethyl bromide derivative (0.4 mmol), allyltributyltin (0.8 mmol), and AIBN (5 mol%) in dry benzene (3 ml) was degassed by bubbling argon gas for 30 min. The mixture was refluxed for 12 h. After removal of the solvent, aq. KF solution (5 ml) and ether (10 ml) were added to the residue and stirred for one hour. After filtration and separation, the organic layer was dried over Na2S04. After removal of the solvent, the residue was chromatographed on silica gel using ethyl acetate/hexane to afford a diallyl product [95]. 

Vapor phase thermolysis of 2,5-hexadien-l-ols at 260°C affords cyclopropylmethyl ketones . The reaction has been proposed to proceed via homodienyl migration of hydrogen and is stereospecific (equation 118). l-(l-Alkynyl)-2-vinyloxiranes undergo successive Cope rearrangements at 300-350°C to give 2-(l-alkynyl)cyclopropane-carbaldehydes (equation 119) . Acid-catalyzed intramolecular acetalization followed by... 

Finally, reduction of ( —)-methyl (15,35)-(2,2-dimethyl-3-tosyloxycyclobutyl)acetate with lithium aluminum hydride or sodium borohydride afforded a mixture of products among which ( —)-(lS,2i )-2-(2-isopropylcyclopropyl)ethanol (4) predominated. The nature of the products is indicative of a cyclobutyl-cyclopropylmethyl homoallylic type rearrangement. 

The cyclobutyl-cyclopropylmethyl rearrangement of 2-oxabicyclo[4.2.0]octan-3-ones 7 is strongly dependent on their substitution pattern at the bridgehead positions.When unsubstituted or monomethyl-substituted -lactones are treated with acetic acid or 4-toluenesulfonic acid under reflux, no rearrangement occurs. However, under similar conditions dialkyl-sub-stituted lactones lead to an almost quantitative yield (at 20-40% conversion) of y-lactones 8. 

Electrophilic ring opening of bicyclo[l. 1.0]butanes generally leads to mixtures of cyclobutyl, cyclopropylmethyl and allylmethyl compounds, among which the first two products dominate.The parent bicyclo[1.1.0]butane (1) is converted into cyclobutanol and cyclo-propanemethanol, without formation of any but-3-en-l-ol, upon treatment with 0.001 N sulfuric acid. Acetolysis of bicyclo[1.1.0]butane affords a mixture of all three acetates. In general, the product ratio is highly dependent on the substitution pattern of the bicyclic system. 

Electrophilic additions to bicyclo[1.1.0]butanes are highly stereoselective. Protonation occurs predominantly with retention of configuration and leads to proton incorporation cis to the methyl moiety. Thus, acetolysis of l,2,2-trimethylbicyclo[1.1.0]butane (5) in acetic acid-d leads to the monodeuterated cyclopropylmethyl compounds 6 and 7 with retention of configuration. ... 

Various alkyl cyclopropylmethyl ketones and cyclopropylacetaldehydes have been converted to 2-cyclopropylalk-l-enyl derivatives, including acetates,chlorides,tri-... 

The oxidation of cyclobutanemethanol and a,a-dimethylcyclobutanemethanol with lead tetra-acetate in benzene gave the same product distributions within the isomeric homoallylic, cyclobutyl and cyclopropylmethyl actates. The distribution was the same in the oxidation of cyclobutane carboxylic acid, suggesting that alcohol p-cleavage and acid decarboxylation gave rise to the same radical species. 

Aldehydes, acetals, and acid chlorides have been cyclopropylmethylated stereo-selectively with homoallylstannanes, exploiting the y-effect of tin " a Lewis acid-promoted allylation of aldehydes with allyltin shows stereospeciflcity, as does an addition of highly substituted cyclic aUylzinc reagents. ... 

In comparison with other experimental data, the rates of solvolysis of (496) and (497) allowed an estimation of 14kcalmol for the energy barrier to rotation about the bond which joins the cyclopropyl to the formal secondary carbonium ion of a cyclopropylmethyl cation. This is in good agreement with calculated values and other experimental results. Acid-catalysed solvolysis of the unsaturated compounds (498) gives a mixture of unrearranged products. The stereochemistry of the products exo.endo ca. 85 15) was only slightly affected by the solvent (acetic acid or methanol) and not at all by... 

Butyl-lithium abstracts a proton from 5,6-dihydro-2/f-pyran to give (515) which isomerizes to a cyclopropyl enolate which could be trapped with acetic anhydride or, better, with trimethylsilyl chloride. Nerol oxide similarly gives an alkyl-lithium which undergoes a 1,4-carbon shift to yield a cyclopropyl enolate. The lithium-induced reduction of cyclopropylmethyl mesitoates... 

The intermolecular reaction of oxocarbenium ions with simple alkenes, less reactive carbon nucleophiles, is generally slow and inefficient. A recent paper has described that the (la)-promoted intermolecular reaction of acetals with vinylcyclopropane (22) gives 3,6-heptadienyl ethers (23) with high E selectivity [74]. The allylation mechanism involves the formation of a cyclopropylmethyl cation intermediate and its ring opening (Scheme 9.21). Homoallylstannane (24) also adds to the oxocarbenium ion generated from benzaldehyde dimethyl acetal and (la) [75]. 

A rather unique example is provided by a 5-hydrogen abstraction of an acetal hydrogen the 1,5-biradical so formed both cyclizes and undergoes P-elimination at the dioxy radical site to produce a 1,3-biradical that cyclizes to a cyclopropylmethyl formate ester. 

---