Methyl-cyclo-propane

Ethyl 1 -[diallyl(hydroxy)methyl]cyclo-propane-l-carboxylate was also formed. 

It is evident from Table 10 that identical mixtures of cis- and trans-cyclo-propanes obtained from either cis- or trans-olefins are quite rare. Only the cyclohexanone-carbene 59 and methyl-bisalkoxy-carbonyl-carbene 3) give... 

HsCs-CHs-° h i J 1. NaH/DMF/ C2H5-SH (- C2Hs —SNa) 20-25°, 30 min 2. H20 3. isolieren als 4-Methyl- benzolsuIfonsaure-Salz) ( E)-l-Amino-2- (3,4-diben-zyloxy-phenyl)-cyclo-propan 74 1... 

Das durch alkalischen RingschluB von l-Benzylimino-3-chlor-2,2-dimethyl-l-phenyl-(bzw. 4-methyl-phenyl)-propan erhaltene 1-Aryl-1-benzylidenamino-2,2-dimethyl-cyclo-propan wird sauer zu 1-Amino-2,2-dimethyl-1-phenyl (bzw. 4-metkyl-pkenyl)-cyclopropan hydrolysiert3. 

The reaction proceeded with extremely high syn diastereocontrol with five- and six-membered cyclic allylic alcohols with a variety of zinc carbenoids. One particnlarly interesting example of a highly functionalized starting material is in the introduction of the C19 methyl group of taxusin through a highly chemo- and diastereoselective cyclo-propanation (equation 50). ... 

The fluorophenol could be converted into 56 in four good steps but the insertion of the vinyl group to give 57 by formylation and a Wittig reaction went in only 18% and the cyclo-propanation with a diazoester and Cu(I) (chapter 30) gave poor selectivity in favour of the cis isomer of 57. Worse still, it was necessary to protect the phenol as a methyl ether and the removal of the methyl group, the last step, went in only 52% yield, wasting nearly half of all the material. 

Michael P. Doyle, William R. Winchester, Marina N. Protopopova, Amy P. Kazala, and Larry J. Westrum 13 (1 R,5S)-(-)-6,6-DIMETHYL-3-OXABICYCLO[3.10]HEXAN-2-ONE. HIGHLY ENANTIOSELECTIVE INTRAMOLECULAR CYCLO-PROPANATION CATALYZED BY DIRHODIUM(II) TETRAKIS[METHYL 2-PYRROLIDONE-5(R)-CARBOXYLATEl... 

Methyl-6-methylen-2-oxo- E21c, 3045 (cycl. En-on + Methylen-cyclo propan)... 

Bicyclo 4.1.0]heptan 7-Trimethyl-silylcarbonyl- E17b, 1393 (7-Br/7-SiR3 — 7-H/7-CO—SiR3) Cyclohexan trans-2-Hydroxy-1-(trimethylsilyl-ethinyl)- E19d, 146 (sp-CH - C - Li/Oxiran) Cyclopenten 2-Ethyl-4-methylen-l-trimethylsilyl- E17c, 2251 (Methylen-cyclo propan + In) Ethen l-(l-Cyclohexenyl)- -trimethylsilyloxy- E1S/1, 441 (Keton 4- RjSi—O —S02 —R) Furan 2-Methyl-5-propyl-3-trimethylsilyl- E18, 674 (In-Hydromagnesier./+ R —CN)... 

Spiro 6.6 tridec-2-en 6-Oxo- E17c, 2595 (2-Acyl — 1-etheny] — cyclo-propan/Li —NR2 + R3Si —Cl) Tricyclo[4.4.2.0l6]dodecan 11 (or 12)-Methylen-2-oxo- E21c, 3104 (bicycl. En — on + Allen) Tricyclo 6.4.01 s]dodecan 8-Methyl-... 

Use of ( )-l,4-dibromobut-2-ene in the SIRC reaction gives rise to vinylcyclopropanes (Table 7). The cyclopropanation is induced by bases such as sodium ethoxide, sodium hydride or sodium amide or can be carried out under phase-transfer conditions. The reaction is non-stereoselective however, a diastereomeric excess of 39-80% was obtained with nucleophiles containing a chiral auxiliary. When cyclic ketones are used as nucleophiles, spiro-cyclo-propanes, which serve as precursors for (Z)-jasmonate or methyl jasmonate (Table 7, entries 5-7), are formed. 

The combination of diethylzinc and chloroiodomethane was employed in the synthesis of carbo-cyclic cyclopropyl nucleosides projected for biological evaluation. Attempts to cyclopropanate the intermediate a,j8-unsaturated ester, methyl (Z)-4,5-(isopropylidenedioxy)pent-2-enoate, gave a low yield (10%) of the desired cyclopropyl product. However, hydroxy-directed cyclo-propanation vide infra) of the reduced allyl alcohol 21 with diethylzinc/chloroiodomethane at 0°C afforded the cyclopropane derivative 22 in 54% yield. 

With the ruthenium(I) catalyst [(OC)4Ru2(OAc)2]n (see Section 1.2.1.2.4.2.6.3.1.), cis selectivity was observed in cyclopropanation of trisubstituted alkenes (e.g. 2-methylbut-2-ene, 2,5-dimethylhexa-2,4-diene) with methyl diazoacetate. Furthermore, the interplay between steric, electronic, and lipophilic interactions can occasionally result in enhanced cis selectivity for an individual reaction. Notably, certain homoallyl chlorides were consistently cyclo-propanated by diazoacetates with pronounced cis selectivity in the product cyclopropanes 4 with various catalysts. 

The transition-metal-catalyzed decomposition of methyl trialkylsilyldiazoacetates 5 in the presence of styrene, hex-l-ene and cyclohexene has been studied.In all cases, where cyclopropanation occurs, the formation of the thermodynamically favored cyclopropane dia-stereomers E-6 and anti-1 are formed predominantly. The steric demand of the trialkylsilyl substituent has a relatively small influence on the diastereoselectivity on the other hand, catalytic cyclopropanation with the triisopropylsilyldiazoacetate is more difficult than with 5 (R = Me, Et) or fails completely. Copper(I) triflate is a more efficient catalyst for these cyclo-propanations than rhodium(II) acetate dimer and rhodium(II) bis(perfluorobutanoate) dimer the catalyst [Ru2(CO)4(/i-OAc)2] gives somewhat better results than copper(I) triflate for hex-l-ene, but not for styrene. The catalytic cyclopropanation of cyclohexene with 5 (R = Me, Et) to give bicyclo[4.1.0]heptanes 7 succeeds only with [Ru2(CO)4(/j-OAc)2] as catalyst. ... 

Irradiation at 350 nm of 1,1-dibromocyclopropanes dissolved in liquid ammonia or dimethyl sulfoxide in the presence of sodium benzenesulfanate leads to l,l-bis(phenylsulfanyl)cyclo-propanes. The yields are in all cases below 50% which is due to both decomposition of the product on longer irradiation and formation of significant amounts of cyclopropyl phenyl sulfide. Most 1,1-dichlorocyclopropanes are unreactive, and no reaction occurs in the presence of oxygen, di- erf-butyl nitroxide and 1,3-dinitrobenzene, which supports the notion that the reaction is a radical process. The cleanest reaction took place during irradiation of 2,2-dichloro-1 -methylcyclopropanecarbonitrile, which gave no sulfide, little unreacted starting material, and 1-methyl-2,2-bis(phenylsulfanyl)cyclopropanecarbonitrile (4) in 47% yield. 

Several reagents have been used for the dehydrobromination of bromocyclopropanes to prepare substituted alkylidenecyclopropanes. For example, powdered potassium hydroxide and quartz sand were employed at 90 C and at low pressure in the preparation of (bromomethylene)cyclo-propane (15) from l-bromo-l-(bromomethyl)cyclopropane(14). Similar procedures resulted in l-(bromomethylene)-2-methylcyclopropane (17, as a 90% pure Z/E mixture) " and [bro-mo(cyclopropylidene)methyl]benzene (19). ... 

Some time ago it was found that a catalytic amount of concentrated sulfuric acid is an efficient agent for dehydrating a,a-dimethylcyclopropanemethanol (1), giving (l-methylethenyl)cyclo-propane (2) in 80% yield. The method was used more recently to prepare the optically active ester, (-)-methyl (17 ,2/ )-2-(l-methylethenyl)cyclopropanecarboxylate (4), which was obtained in 70% yield from the corresponding hydroxy ester. ... 

A modification of this general procedure was used in the synthesis of (prop-2-enylidene)cyclo-propane (allylidenecyclopropane, 12).Allyl bromide was first alkylated in 81 -90% yield with l-lithio-l-(phenylsulfanyl)cyclopropane (10) in the presence of copper(I) iodide or cop-per(I) iodide-dimethyl sulfide. The adduct was then methylated with methyl fluorosulfonate or with dimethyl sulfate, and the sulfonium salt cleaved with powdered potassium hydroxide in dimethyl sulfoxide, to give the product in 50-70% overall yield for the second step. 

Depending on the reaction conditions, the methylation of l,l-bis(diphenylphosphino)cyclo-propane (1) with iodomethane or methyl fluorosulfonate yields the monophosphonium salt 2 or the bisphosphonium salts 3 or... 

The reluctance of phenyl-substituted methylenecyclopropanes to rearrange to products in which the phenyl group is located at the exocyclic methylene group was also demonstrated with l-methylene-2-phenylcyclopropane and l-methyl-2-methylene-l-phenylcyclopropane. When used as single enantiomers, both compounds underwent facile racemization at 100 C in chloroform without formation of benzylidenecyclopropane or (l-phenylethylidene)cyclo-propane. Similar results were obtained when a mixture of as- and tra i-l-methyl-2-methyl-ene-3-phenylcyclopropane (Table 1, R = R = R = R = H R = Me R = Ph) was isomerized under thermal or photochemical conditions. 

The protolytic transformation of homofuran derivative 15 into methyl ( , )-6-oxohexa-2,4-dienoate is one of the key steps in a synthesis of the arachidonic acid metabolite 5-HETE. Activated, low acidity zeolites can be used to induce the isomerization of cyclo-propanes. " ... 

Alkoxycyclopropanes, commonly prepared from alkyl enol ethers by Simmons-Smith cyclo-propanation (Section 1.A.1.2.1.1.), are cleaved by strong acids to the a-methylated carbonyl compound, thus establishing an overall a-methylation of a ketone or an aldehyde, e.g. the sequence 67 -> 68 -> 69 70 71. ... 

Methyl-cyclo- 2-(4-Methyl-cyclohexenyl)-hexyliden)-propanal propanal... 

Tet-ra-methyl-cyelo-propen Benzophenon in Aeeton Philips HPK 125 W Na 16° 48 Stdn. S.CH2-CCCH3 A- 1,2,2,3-Tetra- methyl-l-(2-oxo- propyl)-cyclo- propan 9 O A 1... 

The alkyl substituents in 1-alkyl-l-vinyl and /rfl/7 -l-alkyl-2-vinyl-cyclo-propanes have little effect on reactivity. A cis alkyl substituent may have a profound effect for example, the energy of activation is nearly 20 kcal.mole smaller and the entropy of activation is 10 eu more negative, for isomerization of cis-1 -methyl-2-vinylcyclopropane than for typical vinylcyclopropane rearrangements. Further, the sole product of this reaction is cis-1,4-hexadiene. This and related reactions, which occur by a concerted mechanism involving 1,5-hydrogen migration, are discussed in the next section. 

Asymmetric cyclopropanation. The ability to effect ligand exchange between rhodium(II) acetate and various amides has lead to a search for novel, chiral rhodium(II) catalysts for enantioselective cyclopropanation with diazo carbonyl compounds. The most promising to date are prepared from methyl (S)- or (R)-pyroglutamate (1), [dirhodium(ll) tetrakis(methyl 2-pyrrolidone-5-carboxylate)]. Thus these complexes, Rh2[(S)- or (R)-l]4, effect intramolecular cyclopropanation of allylic diazoacetates (2) to give the cyclo-propanated y-lactones 3 in 65 S 94% ee (equation 1). In general, the enantioselectivity is higher in cyclopropanation of (Z)-alkenes. 

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