Cyclopropanes indenes

The first example of this type of activation was the mechanochemical generation of an acid, developed by Diesendruck et al. Inspired by Craig s gDHC system, they incorporated gm-dichlorotetrahydro cyclopropanated indene into polymethyl acrylate matrix (PMA) and showed that compression resulted in ring-opening of... 

Interest in this reaction was revived when the relevance of a carbene mechanism was realized, particularly following the demonstration (cf. SectionI,B) of a similar ring expansion of indene to 2-chloro-naphthalene by dichlorocarbene via the cyclopropane adduct. Indeed, at this time Nakazaki suggested that these reactions occurred by the addition of dichlorocarbene to the indolyl anion and subsequent rearrangement to the indolenine and, with loss of chloride ion, to the quinoline [Eq. (12)]. The preference of dichlorocarbene for... 

An alternate approach has been developed by Charette and coworkers in which chiral iodomethylzinc phosphates were prepared and tested in the cyclopropanation of unfunctionalized alkenes. Although these reagents were not sufficiently reactive to convert aryl-substituted alkenes (such as indene) to the corresponding cyclopropane, they reacted nicely with protected aryl-substituted allylic and homoallylic alcohols (equation 92) °. Several 3,3 -disubstituted binols were tested and ligand 23 stood out as being the most effective with this class of compounds. The active reagent in this case is a chiral iodomethylzinc phosphate. 

Not much is known about the opening of dihalocyclopropanes by Lewis acids beyond reports on the reaction of dibromo- and dichloro-cyclopropanes with aromatic hydrocarbons under the influence of AlCb or FeCb leading to indenes.229"231... 

Laqua, H. Frohlich, R. Wibbeling, B. Hoppe, D. Synthesis of enantioenriched indene-de-rived bicyclic alcohols and tricyclic cyclopropanes via (-)-sparteine-mediated lithiation of a racemic precursor and kinetic resolution during the cyclocarbolithiation. J. Organomet. Chem. 2001, 624, 96-104. 

The Lewis acid-catalysed rearrangement of arylvinylidenecyclopropanes having three substituents at the 1- and 2-positions of the cyclopropane to give 6a//-benzole] fluorine or phenyl-l//-indene derivatives via an intramolecular Friedel-Crafts reaction under mild reaction conditions has been reported (Scheme 57).92... 

The ligand was then used to form a variety of transition metal carbene complexes [207] (see Figure 3.72). Interestingly, more than one method for the formation of transition metal carbene complexes was successfully employed presence of an inorganic base (IC COj) to deprotonate the imidazolium salt and the silver(I) oxide method with subsequent carbene transfer to rhodium(I), iridium(I) and copperfi), respectively. The silver(I) and copper(I) carbene complexes were used for the cyclopropanation of styrene and indene with 1,1-ethanediol diacetate (EDA) giving very poor conversion with silver (< 5%) and qnantitative yields with copper. The diastereomeric ratio (endolexo) was more favonrable with silver than with copper giving almost a pnre diastereomer for the silver catalysed reaction of indene. 

The transformation of 14 into 7-methoxy-fra 5-3a,9b-dimethyl-l,3,3a,4,5,9b-hexahydro-2/f-benz[e]inden-2-one (15) illustrates the use of the sequence consisting of cyclopropanation, followed by dissolving metal reduction, for the introduction of angular methyl groups into structures containing condensed alicyclic rings. 

The cyclopropane-containing intermediates were isolated in several cases. Furthermore, it was found that l//-inden-l-ones 13 could be directly ring expanded to 1-naphthols 15 by treatment with lithium methylsulfinylmethanide, without isolation of any of the intermediates. Addition of the inden-l-one 13 to methylsulfinylmethanide, prepared from dimethyl sulfoxide and butyl-lithium, gave after 24 hours, a mixture of the 1-naphthol 15 and the j8-hydroxy sulfoxide 16. ... 

In some cycloadditions of cycloproparenes, secondary products derived from opening of the cyclopropane bond were observed. The reaction of benzocyclopropene with buta-1,3-diene gave the expected bicyclo[4.4.1]undeca-l,3,5,8-tetraene(5)in 6% yield 2-vinyl-2,3-dihydro-17/-indene (43%) and 8,9-dihydro-5/7-benzocycloheptatriene (10%) were also obtained which are believed to arise via a competing radical pathway. ... 

Methyl-phenyl- 3099 C, H,Br Cyclopropane l-(a-Bromo-benzyl)- 1445 Indene... 

The cyclopropanation of styrene with f-butyl diazoacetate in the presence of 5 mol % of (salen)Co(III) bromide 23 produced the corresponding trans-cyclo-propane-carboxylate, with high diastereomeric ratio and enantiomeric excess (Eq. (5)). The asymmetric cyclopropanations of other styrene derivatives also showed high enantioselectivities as well as high transxis selectivities. However, the reaction of disubstituted olefins, such as indene, was sluggish. The use of Co(III) instead of Co(II) seemed to be critical, since Nakamura reported that much lower enantioselectivities were observed with optically active (salen)co-balt(II) complexes. 

Conjugated dienes can be regioselectively cyclopropanated at the terminal double bond with excellent chemoselectivity to produce the corresponding vinylcyclopropanes 27 and 28 in 86% yield and with a moderate diastereomeric ratio, Eq. (8). The enantioselectivity for the trans isomer 27 was excellent. On the other hand, P-methylstyrene, 2,5-dimethyl-2,4-hexadiene, cyclopentene, and indene could not be cyclopropanated under the same reaction conditions. 

M ethyl-butadicn-( 1,2)-1 - -dimethylester 1360 3- Methyl-inden-1 - -dimethylester 1360 3-Methyl-3-phenyl-cyclopropan- -di methylester 1360 Naphthalin-N- -dimethylestcr 1374 3-Oxo-2-methyl-butan-2- -isopropylester 1373 Thiophen-2- -dimethylcstcr 1374 Trichlormetlian- -mono-(2-melhyl-propylester) 1375 2,3.4-Trimethy)-penten-4- -methylester-amid 1362... 

When copper catalysed, indene for instance reacts with diazoacetates to give either exo- or enrfo-cyclopropanes (see Figure 7.26). ° The distinct difference in the selectivities achieved by using different concave 1,10-phenanthrolines lies in the different geometry of the ligands. 

Figure 7.26 When concave 1,10-phenanthrolines are used as ligands for copper(l) ions in the cyclopropanation of indene by diazoacetates, the exo/endo-selectivities can be controlled by the choice of the ligand. The concave 1,10-phenanthroline from Figure 7.10 [X = (Cff2hol in combination with ten-butyl diazoacetate is highly exo-selective (exo/endo = 140 1) while the 1,10-phenanthroline bridged calix[6Iarene from Figure 7.15 is endo-selective (best results for N2CHCOOMe, exo/endo = 14 86) °...

The calix[6]arene 65 bridged by a 1,10-phenanthroline was synthesized from p-bu -calix[6]arene and 2,9-bis(bromomethyl)-l,10-phenan-throline (97TL4539). Its complex with Cu has been beneficially used for Cu catalyzed cyclopropanation of styrene and indene. Several chiral derivatives of 65 have been synthesized but the stereoselectivity of cyclopropanation, catalyzed with their Cu complexes, could not be enhanced (2006EJ04717). A similar bridging of calix[5]arene and calix[8]arene has also been investigated (2005EJ02330). 

Friedel-Crafts alkylations of chlorobenzene, chloropropylbenzenes, and p-xylene by cyclopropane have been examined, employing sulphuric acid and aluminium trichloride as catalysts. The alkylation of benzene, toluene, and anisole by 1-bromo-1-fluorocyclopropane results in indanes, indenes, and alkenylbenzenes. Intramolecular acylation of (183) affords products of attack at C-1 and C-2 of the cyclo-... 

---