Reactions cyclopropa naphthalene

Reductive 1,2-eIimination of chlorine and bromine from adducts of l-bromo-2-chlorocyclo-propene (see Section 5.2.2.1.2.5.) with oxygen and sulfur hetarenes has served in the synthesis of a number of cycloproparenes. This transformation is effected by low-valent titanium together with lithium aluminum hydride or an organolithium compound. Thus, reaction of the adduct 3 of l-bromo-2-chlorocyclopropene and 1,3-diphenylisobenzofuran with tita-nium(III) chloride and lithium aluminum hydride overnight in tetrahydrofuran led to elimination of both halogens together with extrusion of the oxygen and formation of 2,7-diphenyl-l/f-cyclopropa[ ]naphthalene (4) in 72% yield. 

Similarly, alkane- and arenesulfonyl isocyanates gave 2-sulfonyl-2,3-dihydroisoindol-l-ones 11 with benzocyclopropene. 2,3-Dihydroisoindol-l-one was produced as a byproduct in 4% yield in the case of arenesulfonyl isocyanates. Cyclopropa[ ]naphthalene underwent addition to 4-phenyl-47/-l,2,4-triazole-3,5-dione at 20°C almost instantaneously to give an indazole 12 in 92% yield.Both reactions are believed to occur by electrophilic attack on the cyclo-proparene and may involve a zwittcrionic intermediate. When benzyne was generated from benzenediazonium-2-carboxylate in refluxing dioxane in the presence of cyclopropa[Z ]naph-thalenc, 5//-naphtho[2,5-a]indene was formed in 13% yield. 

Attempted formation of t/ -tricarbonylchromium(0) complexes of cyclopropa[/)]naphthalene (3) or l/f-cyclopropa[6]anthracene (7) by reaction of these ligands with tris(acetonitrilc)tricar-bonylchromium(O) resulted in the formation of the corresponding annulated cyclobutenone derivatives 6 and 8 in 57 and 54% yield, respectively, as the result of carbonyl-insertion reactions. 

In contrast, isomers of 115 have so far not been isolated. An early attempt to generate cyclopropa[a,e]naphthalene (118) failed. More recently, the generation of dicyclopropa[a,c]naphthalene (119) was attempted by reaction of 120 with base. When the aromatization was carried out in the presence of DPIBF (44), stereoi-someric bis-adducts of cyclopropenes were isolated. However, the adducts provide no evidence for the formation of 119 as a reactive intermediate, since they are formed by sequential elimination-cycloaddition via 121. Cyclopropene interception of 121 is faster than further elimination to 119. The failure of the reaction to produce 119 has been attributed to the high strain energy of the product, which is estimated some 2 8 kcal/mol higher than that expected for two isolated cyclopropene units. ... 

Diphenylisobenzofuran (DPIBF, 44) or furan have been used to intercept cyclopropa[fl]naphthalene (56) and cyclopropa[/]phenanthrene (142). ° ° DPIBF (44) reacts with 1 in THF at 20 °C to form exo and endo adducts 321 and 322 217 unsymmetrical adduct 323, resulting from ring-opening of 1, may also be obtained if the reaction is carried out in CHCl, in particular at higher temperatures." " ... 

When the double bond formed is conjugated to an aromatic ring, the yield can be much higher. Thus, a 97% yield of la,7b-dihydro-7b-(benzenesulfonyl)-l//-cyclopropa[a]naphthalene (4) was obtained by reaction of the corresponding bromo compound 3 and potassium /er/-butoxide in tetrahydrofuran. ... 

While the double dehydrochlorination of 1,1-dichlorocyclopropane derivatives has proved successful in the preparation of a variety of cyclopropabenzenes and cyclopropa[6]naphthalenes (Table 7), the reaction fails to provide cyclopropa[a]naphthalenes, cyclopropanthracenes or higher derivatives. In these cases only substituted arenes arising from the opening of the cyclopropane ring were obtained. For the preparation of lFf-cyclopropa[<2]naphthalene a retro-Diels-Alder reaction was used (see Section 5.2.2.6.). 

Notably, the strongly basic conditions used in the reaction do not lead to rearrangement of double bonds present elsewhere in the molecule. Thus, a 57% yield of 3,6-bis(methylene)-3,4,5,6-tetrahydro-177-cyclopropa[/i]naphthalene (15) was obtained, in which the exocyclic double bonds did not undergo isomerization to give 3,6-dimethyl-l//-cyclopropa[6]naphthalene. ° ... 

Similar reaction of the adduct 5 with unsubstituted isobenzofuran was more involved. With lithium aluminum hydride, a 60% yield of a 1 3 mixture of 1//-cyclopropa[6]naphthalene (6) and 2-methyl- and 2-chloro-3-methylnaphthalenes (7) was obtained after 18 hours. The corresponding bromomethylnaphthalene 7 (X = Br) was also observed after a reaction time of only 2 hours. Use of butyllithium instead of lithium aluminum hydride improved the ratio of 6/7 to 3 1, while methyllithium gave a 60% yield of the cyclopropanaphthalene uncontaminated by methylnaphthalenes. ... 

Ring contraction of tetrabromobenzocycloheptenedione provided the l//-cyclo-propa[6]naphthalene skeleton 2. Aromatization to the cycloproparene 3 was effected via reduction of the carbonyl groups to alcohols, conversion to p-toluenesulfonates and subsequent reaction with butyllithium. In contrast, the ring contraction of 5,7-dibromodibenzo[n,c]cy-cloheptadien-6-one 4 gave none of the expected 1 //-cyclopropa[/]phenanthren-l -one. The products of the reaction were derivatives of phenanthroic acid, and the cycloproparenone was probably not a reaction intermediate. ... 

Several extensions of this approach have been attempted, but none was successful. Only a faint odor results from the attempted synthesis of cyclopropa[Z)]naphthalene and none of the expected cyclopropa[a]naphthalene or cyclopropa[/]phenanthrene were generated in the corresponding reactions.- The same difficulties have been experienced with other benzyl derivatives. The reaction of 2-bromobenzyl bromide, 2-bromobenzyl chloride and 2-iodobenzyl bromide with butyllithium gave (partially) reduced bibenzyls or 9,10-dihydroanthracene, but no benzocyclopropene. Similarly, lithiation of 2-bromobcnzylsulfonates afforded only trace amounts (< 5%) of bcnzocyclopropene, while only methoxymethylbenzene was isolated on treatment of l-methoxymethyl-2-trimethylsiIylbenzene with fluoride ions. ... 

The dihalocyclopropane route is the method of choice for the synthesis of benzocyclopropenes and linearly fused cyclopropanaphthalenes, but is unsuccessful for angular cyclopropa[u]naph-thalene. Treatment of l,l-dichloro-la,2,3,7b-tetrahydro-l/f-cyclopropa[a]naphthalene(5) with potassium /ert-butoxide gave a mixture of 1-chloromethylnaphthalene, 1-terr-butoxymethyl-naphthalene and 2-terf-butoxy-l-chloromethylene-l,2,3,4-tetrahydronaphthalene, but none of the expected cyclopropa[n]naphthalene. The failure of the reaction has been attributed to difficulties in the aromatization. Isomerization of the initially produced cyclopropenyl double bond into the cyclohexane ring would require disruption of the aromatic character of the adjacent benzene nngT t-r>> 62 Similarly, attempted aromatization of l-chloro-l,2,3,7b-tetra-hydro-l//-cyclopropa[a]naphthalene (6) with 2,3-dichloro-5,6-dicyanobenzoquinone or via N-bromosuccinimide bromination followed by reaction with base afforded 4,5-benzotropone instead of cyclopropa[fl]naphthalenc. ... 

Similarly, 1,1 -dihalocyclopropa[A]- and cyclopropa[a]naphthalenes ° were ionized to the corresponding cyclopropanaphthalenylium ions the ions derived from the cyclopropa[ ] isomer are, however, very short-lived. On the other hand, when l,l-dihalocyclopropa[T7]anthracenes were reacted under the same reaction conditions, no ions were observed and the compounds decomposed. 

Benzocyclopropene reacts with a variety of radical reagents (for example A -bromosuccinimide carbon tetrachloride bromotrichloromethane bromoform/benzoyl peroxide alkyl sulfide and ethane-1,2-dithiol with photolysis) to afford products derived from cleavage of the cyclopropane ring. The preferential mode of reaction consists of a chain reaction initiated by radical addition at Cl a followed by opening of the cyclopropyl radical to afford a benzyl radical. Yields are generally low except for the addition of the alkylsulfanyl radical, e.g. formation of 1, and no products derived from addition to the central tt-bond are formed. Cyclopropa[A]naphthalene reacts similarly with radicals and gives 2-methylnapthalene derivatives, while no addition to the central 7i-bond is observed. ... 

Alkylidenecycloproparenes react in cycloadditions either with the exocyclic double bond, or with the bridging 7t-bond, When l-(diphenylmethylene)benzocyclopropene reacted with 1,3-diphenylisobenzofuran, a crystalline 1 1 euofo-cycloadduct 20 was produced, which resulted from reaction with the central 7i-bond. ° In contrast, cycloaddition of l-(diphenylmethyl-ene)cyclopropa[Z)]naphthalene to 1,3-diphenylisobenzofuran proceeded via attack at the exocyclic double bond and resulted, ultimately, in a l-(diphenylmethylene)cyclobuta[i]naph-thalene derivative 21. ° ... 

Cyclopropa[6]naphthalene (3) reacts with nonacarbonyldiiron in dichloromethane at 25 °C resulting in a ring expansion by insertion of a — C(0)Fe(CO)4— fragment to yield 4 in 27% yield, the driving force of the reaction is strain relief of the cyclopropene moiety in 3. ... 

Studies on naphthalenes fused to alicyclic rings have been reported. Dehydrochlorination of the tetrahydro-cyclopropa[f>]napthalene (332) with KOBu gave a high yield of the gem-dichlorocyclopropa[f>]naphthalene (333) while l,2,3,4,7,8,9,10-octahydrodicyclohepta[i/e, //Jnaphthalene and 2,7-dimethyl-pyrene (335) are obtained by the reaction sequence shown in Scheme 43. 

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