Dibromo 3-cyclopropane

Cyclopropane, 1,1 -dibromo-2,2-diplienyl-[Benzene, l,l -(2,2-dibromocyclo-propylidene)bis-], 32 Cyclopropanecarboxyltc acid, 70 Cydopropanes, gem-dihalo, 32 CYCLOUNDECANONE, 107 Cycloundecanone, 2-hydroxy-, 110 Cycloundecene, 1-carboxy- [1-Cyclo-undecene-1-carboxylic acid], 111 Cycloundecene, 1-methoxy-, 111 1-Cycloundecene-l-carboxyhc acid, methyl ester, 108... 

Longifolene has also been synthesized from ( ) Wieland-Miescher ketone by a series of reactions that feature an intramolecular enolate alkylation and ring expansion, as shown in Scheme 13.26. The starting material was converted to a dibromo ketone via the Mr-silyl enol ether in the first sequence of reactions. This intermediate underwent an intramolecular enolate alkylation to form the C(7)—C(10) bond. The ring expansion was then done by conversion of the ketone to a silyl enol ether, cyclopropanation, and treatment of the siloxycyclopropane with FeCl3. 

NHase from Rhodococcus. sp. AJ270 was isolated, purified, and applied to the enantiose-lective transformation of a series of cyclopropane carbonitriles. Amides with moderate ee were isolated from conversion of many of the cyclopropane substrates, to yield the amides trans-( IR, 2/ )-3-phenylcyclopropane carbonitrile (49% conv. 22.7% ee), trans-( IS, 35)-2,2-dimethyl-3-phenylcyclopropanecarbonitrile (40% conv. 84.7% ee), trans-( IR, 3/f)-2,2-dibromo-3-phenylcy-clopropanecarbonitrile (11.6% conv. 83.8% ee), cis-( IR, 25)-3-phenylcyclopropanecarbonitrile (25.8% conv. 95.4% ee), and cis-(lR, 2S )-2,2-dimethyl-3-phenylcyclopropanecarbonitrile (7.9% conv. 3.2% ee) [43],... 

Low intensity ultrasound has also been applied to the Simmons-Smith cyclopropanation of olefins with zinc-diiodomethane (237). This reaction normally will not occur without activation of mossy Zn with I2 or Li, and was difficult to scale-up due to delayed initiation. Yields upon sonication are nearly quantitative, activation of the Zn is unnecessary, and no delayed exotherms are observed. In reactions with another class of organic dihalides, ultrasonic irradiation of Zn with a,a -dibromo-o-xylene has proved a facile way to generate an o-xylylene-like species [Eq. (49)],... 

Various alkyl- and aryl-substituted [3]radialenes could be prepared from 1,1-dihaloal-kenes using organometallic pathways. Hexamethyl-[3]radialene (25), the first [3]radialene to be synthesized, was obtained in a very low yield by treatment of l,l-dibromo-2-methyl-1-propene (22) with butyllithium8,9. The lithium carbenoid 23 and the butatriene 24 are likely intermediates of this transformation (Scheme 2), the former being the source of an unsaturated carbene moiety which is transferred onto the latter. However, the outer double bonds of 24 are more readily cyclopropanated than the central one. 

A. 1,1-Dibromo-2,2-bis(chloromethyl)cyclopropane (1). Into a 1-L, threenecked, round-bottomed flask, equipped with an efficient mechanical stirrer, a thermometer, and a condenser equipped with a potassium hydroxide drying tube, are placed 54.1 g (0.403 mol) of 3-chloro-2-(chloromethyl)propene (Note 1), 212 g (0.805 mol) of bromoform (Note 2), 1.70-2.00 g (14.4-16.9 mmol) of pinacol (Note 3), and 1.45 g (3.94 mmol) of dibenzo-18-crown-6 (Note 4). With very vigorous stirring (Note 5), 312 g of an aqueous 50% sodium hydroxide solution that has been cooled to 15°C is added in one portion. The reaction mixture turns orange, then brown, then black within 5 min, and the temperature of the reaction mixture begins to rise. Within 20 min, the internal reaction temperature is 49-50°C at which point the reaction flask is cooled with a room-temperature water bath, and the reaction temperature decreases to ca. 

Reactions that were stirred for up to 5 or 6 days had slightly higher yields (up to 80%) and needed minimum purification. Reactions that were stirred for less than 3 days or more than 6 days had slightly lower yields (60% after recrystallization). The checkers found that distilled 1,1-dibromo-2,2-bis(chloromethyl)cyclopropane was sufficiently pure (1H NMR and mp) for the subsequent step and did not require recrystallization. The procedure has been carried out on a 1-mol scale with comparable results. 

This preparation of 1,1 -dibromo-2,2-bis(chloromethyl)cyclopropane is a modification of the method reported by Szeimies and co-workers,6 and represents a significant improvement in both the convenience of the workup and the yield of the reaction. In the present method, dilution and filtration of the reaction mixture leave behind a mostly solid residue from which the product is easily obtained. Most significantly, the problematic emulsion that forms in the Szeimies method is effectively eliminated. 

Dibromo-2,2-bis(chloromethyl)cyclopropane Cyclopropane, 1,1-dibromo-2,2-bis(chloromethyl)- (11) (98577-44-7)... 

Azatricyclo[2.2.1.02 6]hept-7-yl perchlorate, 2368 f Azetidine, 1255 Benzvalene, 2289 Bicyclo[2.1.0]pent-2-ene, 1856 2-/ert-Butyl-3-phenyloxaziridine, 3406 3 -Chloro-1,3 -diphenyleyclopropene, 3679 l-Chloro-2,3-di(2-thienyl)cyclopropenium perchlorate, 3388 Cyanocyclopropane, 1463 f Cyclopropane, 1197 f Cyclopropyl methyl ether, 1608 2,3 5,6-Dibenzobicyclo[3.3.0]hexane, 3633 3,5 -Dibromo-7-bromomethy lene-7,7a-dihy dro-1,1 -dimethyl-1H-azirino[l,2-a]indole, 3474 2.2 -Di-tert-butyl-3.3 -bioxaziridinc, 3359 Dicyclopropyldiazomethane, 2824 l,4-Dihydrodicyclopropa[ >, g]naphthalene, 3452 iV-Dimethylethyl-3,3-dinitroazetidine, 2848 Dinitrogen pentaoxide, Strained ring heterocycles, 4748 f 1,2-Epoxybutane, 1609 f Ethyl cyclopropanecarboxylate, 2437 2,2 -(l,2-Ethylenebis)3-phenyloxaziridine, 3707 f Methylcyclopropane, 1581 f Methyl cyclopropanecarboxylate, 1917 f Oxetane, 1222... 

The reactive substrate (0.1 mol), CHBrI2 (10.3 g, 0.03 mol) TEBA-C1 (0.4 g, 1.7 mmol) in CH,C12 (50 ml) are stirred with aqueous NaOH (50%, 60 ml) for 17 h at room temperature. The reaction mixture is worked up as described in 7.1.11 to give a mixture of cyclopropanes (-20%) in which the 1-bromo-l-iodo derivative predominates over the 1,1-dibromo derivative by a ratio of ca. 2 1. The di-iodo compound is observed in only trace amounts (when CHBr2I is used, the dibromo derivative predominates). 

The formation of cyclopropane by reduction of 1,3-dibromopropane was discovered in 1887. Dissolving metals, in particular zinc dust in ethanol, were employed as an electron source [88], Electrochemical reduction in dimethyl-formamide at a mercury cathode has been found to give good yields of cyclopropane [89, 90], 1,3-dibromo, 1,3-diiodo and l-chloro-3-iodopropane all give greater than 90 % yield of cyclopropane, the other product being propene. 

Treatment of the bicyclic dibromo-y-lactone 1 with DBU in acetonitrile at 0-20 °C gave the tricyclic lactone 2 with formation of the cyclopropane ring in 90% yield66. 

Phenyl-1,2-propadiene, b.p. 64°-65°C (11 mm), d4 1-5809, is obtained in a similar manner in 82% yield by the reaction of l,l-dibromo-2-phenyl-cyclopropane with methyllithium at —60°C. 

Skattebol [12], on the other hand, could not detect such carbene intermediates by their addition product (spiropentanes) to olefins using gem-dibromo-cyclopropanes derived from noncyclic olefins. 

Skatteb0l rearrangements in more complex dibromo-vinylcyclopropanes have also been reported. Thus, either a system consisting formally of two double bonds and one dibromocyclopropane unit or an educt containing two dibromo-cyclopropane moieties and one double bond undergo several carbene-carbene isomerizations upon treatment with methyllithium. In both cases, complex product mixtures arise. 

Analogous ionic ring-openings have been described for polycyclic gem-dibromo-cyclopropanes. For example, when solvolyzed in 50% aqueous acetone in the presence of triethylamine, the already mentioned dibromocarbene adduct of benzvalene loses its endo-bromine substituent and opens in a disrotatory fashion to a tricycloheptenyl cation which may be intercepted by water to provide the bromoalcohol shown [175]. 

PENTAMETHYL-, 56, 1 Cyctopentane, acetyl-, 55, 25 Cyclopentane, 1-cyano-l-phenyl-, 55, 94 Cyclopentane, methyl, 55, 62 Cyclopentanol p-toluenesulfonate, 55, 112 Cyclopentene, 56, 34, 58, 73 2-Cyclopenten-l-one, 2,5-dialkyl- 58, 62 CYCLOPENTENONES, 58, 56 Cyclopropane, 1 -acetyl-1 -phenyl-, 55, 94 Cyclopropane, 1, l-dibromo-2,2-diphenyl-, 56, 32... 

A. 1,3-Diacetylbicyclo[1.1.1]pentane (2). I1.1.1]Propellane is generated from 50 g (0.167 mol) of 1.1-dibromo-2,2-bis(chloromethyl)cyclopropane (Note 1) in pentane (Note 2) according to the procedure of Lynch and Dailey.3 To the solution of [1.1.1 Jpropellane, 1 (Note 3), is added 15 mL of freshly distilled 2,3-butanedione and the mixture is irradiated with a 450 W medium pressure UV lamp (Ace Glass Co, catalog no. 7825-34) at -10 5°C for 8 hr (Note 4). Solvents are evaporated on a rotary evaporator. The resulting crystalline material is washed three times with cold 2 1 pentane diethyl ether to give 16.95 g of 1,3-diacetylbicyclo[1.1.1]pentane (2) (Note 5). Another 1 g of the diketone is obtained upon concentration and crystallization of the pentane/diethyl ether rinses. Thus the total yield of 2 is 17.95 g [70% from 1,1-... 

Dibromo-2,2-bis(chloromethyl)cyclopropane was purchased from the Aldrich Chemical Company, Inc. It can be synthesized from 3-chloro-2-chloromethyl-1-propene, available from the Aldrich Chemical Company, Inc., by phase-transfer dibromocyclopropanation.3 5.6... 

Reductive 1,3-elimination reaction of alkyl dihalides constitutes one of the classical methods for the preparation of cyclopropyl derivatives and is particularly useful for the synthesis of highly strained polycyclic hydrocarbons. A new preparation method of [l.l.ljpropellane, more versatile than the original Wiberg s method, has been devised3,4. Thus, treatment of l,l-dibromo-2,2-bis(chloromethyl)cyclopropane with alkyllithium or lithium powder affords [1.1. ljpropellane by two successive 1,3-eliminations of halogens by way of 1 -bromo-2-(chloromethyl)bicyclo[l. 1. Ojbutane (equation 1). This method has been... 

Dihalocyclopropanes containing all possible combinations of halogens have been synthesized. From the vantage point of the synthetic chemist, dibromo- and dichloro-cyclopropanes elicit the most useful and fascinating chemistry, and therefore this discussion will be centered around the formation and transformations of these two groups of compounds. For the sake of completeness, dihalocyclopropenes have been discussed where appropriate. To emphasize the synthetic potential, separate subsections are devoted to certain topics, e.g. formation of heterocycles. 

Dihalocydopropanes readily undergo reductive dehalogenation under a variety of conditions. Suitable choice of reagents and reaction conditions will allow the synthesis of monohalocyclopropanes or the parent cyclopropanes.19 " The ease of reduction follows the expected order I > Br > Cl > F. In general, complete reduction of dibromo and dichloro compounds is accomplished by alkali metal in alcohol,99-102 liquid ammonia103 or tetrahydrofuran (equations 28 and 29).104 The dihalocydopropanes can be reduced conveniently with LAH (equation 30).105 LAH reduction is particularly suited for difluoro compounds which are resistant to dissolving metal reductions.19 106 It is noteworthy that the sequence of dihalocar-bene addition to an alkene followed by the reduction of the dihalocyclopropyl compounds (equation 31) provides a convenient and powerful alternative to Simmons-Smith cyclopropanation, which is not always reliable. 

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