Cyclopropyl benzene

Benzene, bromoethynyl, 46, 86 Benzene, cyclopropyl, 47, 98 Benzene, hexaphenyl, 46, 44... 

Benzene, bromoethynyl, 45, 86 Benzene, 3-bromopropenyl-, 48, 51 Benzene, cyclopropyl-, 47, 98 Benzene, hexaphenyl-, 46, 44 Benzenediazonium, o-carboxy-, hydroxide, inner salt, 48,12 Benzenediazonium-2-carboxylate,... 

Benzene, cyclopropyl-, 44, 30 Benzene, 1-iodo-2,4-dinitso-, 40, 34 Benzene, iodoso-, 43, 60 Benzene, iodoso-, diacetate, 43, 62 o-Benzenedithiol, 49,64 Benzenehexoi, 42, 66 Benzenesulfenyl chloride, 2,4-DINITRO-, 44, 47... 

Hydroxycoumarin treated with K- er -butoxide in terf-butanol, evaporated in vacuo, then treated in dimethyl sulfoxide with 2-bromocyclobutanone in benzene cyclopropyl 4-hydroxy-3-coumaryl ketone. Y 98%. F. e. s. V. S. Velezheva, I. V. Madiinskaya, and V. A. Barkhash, Zh. Vses. Khim. Obsdichest. 14, 467 (1969) C. A. 71, 112747. 

To a solution of 130 parts cyclopropyl-di-(4-fluorophenyl)-carbinol in 240 parts benzene are added dropwise 43 parts thionylchloride. The whole is refluxed until no more gas is evolved. The reaction mixture is then evaporated. The residue is distilled in vacuo, yielding 4-chloro-l,l-di-(4-fluorophenyl)-l-butene, boiling point 165° to 167°C at 6 mm pressure ... 

A solution of a 4-cyclopropyl-l, 5-benzodiazepin-2-one4 (5.7 mmol) anti NCS orNBS (5.7 mmol) in CHC13 (50mL) was refluxed for 4h, cooled and evaporated under reduced pressure. The residue was chromatographed (silica gel) and recrystallized (Et20/benzene). 

The cyclopropanation of 1-trimethylsilyloxycyclohexene in the present procedure is accomplished by reaction with diiodomethane and diethylzinc in ethyl ether." This modification of the usual Simmons-Smith reaction in which diiodomethane and activated zinc are used has the advantage of being homogeneous and is often more effective for the cyclopropanation of olefins such as enol ethers which polymerize readily. However, in the case of trimethylsilyl enol ethers, the heterogeneous procedures with either zinc-copper couple or zinc-silver couple are also successful. Attempts by the checkers to carry out Part B in benzene or toluene at reflux instead of ethyl ether afforded the trimethylsilyl ether of 2-methylenecyclohexanol, evidently owing to zinc iodide-catalyzed isomerization of the initially formed cyclopropyl ether. The preparation of l-trimethylsilyloxybicyclo[4.1.0]heptane by cyclopropanation with diethylzinc and chloroiodomethane in the presence of oxygen has been reported. "... 

The photorearrangement of a dienone was noted<4) as early as 1830 in a study of the sesquiterpene a-santonin (1). However, the structure and stereochemistry of the various photoproducts were not conclusively established until 1965.(6) Upon irradiation in neutral media, a-santonin (1) undergoes rapid rearrangement to the cyclopropyl ketone, lumisantonin (2). However, if the irradiation is not terminated after a short period of time the lumisantonin itself rearranges into a linearly conjugated dienone (3). The dienone (3) can be isolated from the photolysis of either (1) or (2) in benzene or ether. In nucleophilic solvents (alcohol or water) the dienone (3) is also photo-chemically active and is further converted into an ester or an acid (photo-santonic acid) (4). 

The ambivalent aptitude of sulfur [19] to stabilize adjacent anionic as well as cationic centers is a remarkable fact that has shown to be a reliable feature for the assembly of four-membered ring scaffolds utilizing cyclopropyl phenyl sulfides [20]. Witulski and coworkers treated the sulfide 1-69 with TsOH in wet benzene (Scheme 1.19) [21]. However, in addition to the expected cyclobutanone derivative 1-70, the bicyclo[3.2.0]heptane 1-70 was also obtained as a single diastereoisomer, but in moderate yield. Much better yields of 1-71 were obtained using ketone 1-72... 

An early - but mechanistically interesting - construction of a bicyclo[3.1.0]oxa-hexane by a domino radical cyclization was presented by Luh s group [50]. The addition of tributyl tin and AIBN to a solution of bromides 3-111 in refluxing benzene gave 3-114 as single diastereoisomers in acceptable yields via the intermediates 3-112 and 3-113 (Scheme 3.29). It is important that the cyclopropyl carbinyl radical intermediate has the correct stability and reactivity, which is achieved by the a-silyl substituent. 

For example, the fact that ions of m/z [90 + R]+ and [104 + R]+ arise directly from the molecular ions of sulfones (Scheme 5.20) confirms a transformation with a new C-C bond formation between carbon atoms of the small ring and of the second benzene ring prior to the fragmentation of the M+. In this case the cyclopropyl moiety (maybe iso-merized) retains the charge and unpaired electron and attacks the second aromatic ring by a nucleophilic or radical mechanism. 

The next section makes use of the much more recent observation19 that there is a nearly constant difference of the enthalpies of formation of corresponding vinyl and phenyl derivatives. If vinyl relates to cyclopropyl, and vinyl also relates to phenyl, then how do corresponding cyclopropyl and phenyl derivatives relate Conceptually, vinylcyclopropane (10), also identified as 1, X = Cypr and 2, X = Vi) and styrene (11, X = Vi, also identified as 1, X = Ph) are thus relatable. Likewise, relatable are cyclopropylamine (2, X = NH2) and aniline (11, X = NH2)18. This thermochemical comparison of benzene and cyclopropane derivatives is not merely a check of two purported identities in terms of a third, arithmetically derivable, identity. Benzene is the archetypical 7i-delocalized aromatic species from which understanding of this widespread phenomenon evolves. Cyclopropane is the paradigm of cr-aromatic species from which understanding of this more exotic phenomenon evolves20. Benzene and cyclopropane are thus naturally paired as conceptual models for delocalization and aromaticity. Section III discusses these and related issues. 

Earlier in this chapter we talked about the enthalpies of formation of singly and then multiply substituted cyclopropanes and the correspondingly substituted benzenes. It is now time to talk about multiple cyclopropanes and the corresponding benzene derivatives. In Section II.D, the enthalpies of formation of the isomeric (cis)- and (trans)-1,1 2, 1 "-ter-cyclopropyl (9a and 9b) were estimated to be 208 kJ mol 1. It was also asserted that the difference of this value and the enthalpy of formation of bicyclopropyl (8) was nearly identical to the difference of the enthalpies of formation of bicyclopropyl and cyclopropane. Let us now rewrite the oligomerization/dehydrogenation reactions 11a and lib as reactions 31aand31b ... 

We admit to presenting no benzene counterpart for gew-disubstituted cyclopropanes. Then again, there are almost no thermochemical data with which to make comparisons save for the three dimethylcyclopropanes. For example, the enthalpy of formation of 1,1-dichlorocyclo-propane is available as are those of the three dichlorobenzenes, but we lack thermochemical data for the monosubstituted cyclopropyl chloride and for both 1,2-dichlorocyclopropanes. 

Just as the unusual stability and reactivity of benzene are placed into their proper context by comparison with cyclobutadiene and cyclooctatetraene39, the 4 -electron homo-logues of benzene, it is instructive to compare the formally homoantiaromatic bicyclo [3.1.0]hexenyl/cyclohexadieny 1 cation systems with the homocyclopropenium and homo-tropenylium ions (Scheme 14). Such a comparison not only puts in context the properties of the latter two homoaromatic cations, but also reveals a different mode of cyclopropyl conjugation that occurs in the 4 -electron systems. 

The versatile selenenylating agent N-(phenylseleno)phthalimide (NPSP) is an effective carbocyclization mediator, which is capable of effecting acid catalyzed cyclization reactions from open-chain olefins, including the formation of cyclopropanes1. This is demonstrated by the quantitative cyclization of 3-butenyltrimethyltin to (cyclopropyl-methylseleno)benzene upon treatment with 1.1 equivalents of NPSP in CH2C12 at 25 °C under acid (e.g. p-TsOH) catalysis (equation 47). 

Finally, heating a neat 10 1 mixture of dicyclopropylacetylene with Fe3(CO)l2 at high temperature (180 °C) for 2 h afforded [tetrakis(cyclopropyl)cyclopentadienone]Fe(CO)3 together with the uncomplexed hexakis(cyclopropyl)benzene (equation 175)244. 

Noncarbonyl transition metal complexes catalyze dimerization and aromatic cyclo-trimerization of ethynylcyclopropane. The product composition depends on the catalyst and the reaction conditions. Thus, Co(acac)2 in the presence of phosphines and AIEt2Cl afforded either the dimer 1,3-dicyclopropyl-1 -butyn-3-ene or a mixture of 1,2,4- and 1,3,5-tris(cyclopropyl)benzenes, whereas Pd(0 Ac)2 gave the same dimer in the presence of PPh3 but only a tris(cyclopropyl)fulvene in the absence of phosphines (equation 176)245. 

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