Bicyclo heptanes, cyclopropanation

However, cyclopropanation of cyclohexene with methyl (a-diazomethyl)acrylate 3 in the presence of copper(II) trifluoroacetate furnished the 7-exo-substituted bicyclo-[4.1.0]heptane preferentially28). 

It has been pointed out earlier that the anti/syn ratio of ethyl bicyclo[4.1,0]heptane-7-carboxylate, which arises from cyclohexene and ethyl diazoacetate, in the presence of Cul P(OMe)3 depends on the concentration of the catalyst57). Doyle reported, however, that for most combinations of alkene and catalyst (see Tables 2 and 7) neither concentration of the catalyst (G.5-4.0 mol- %) nor the rate of addition of the diazo ester nor the molar ratio of olefin to diazo ester affected the stereoselectivity. Thus, cyclopropanation of cyclohexene in the presence of copper catalysts seems to be a particular case, and it has been stated that the most appreciable variations of the anti/syn ratio occur in the presence of air, when allylic oxidation of cyclohexene becomes a competing process S9). As the yields for cyclohexene cyclopropanation with copper catalysts [except Cu(OTf)2] are low (Table 2), such variations in stereoselectivity are not very significant in terms of absolute yields anyway. 

Bicyclo[3.2.0]heptan-6-ones 10 were obtained by transformation of 2-methoxycyclohex-2-enones 8 to l-methoxybicyclo[4.1.0]heptan-2-ols 9 and subsequent rearrangement (Table 13).155 161 For the synthesis of the requisite precursors, a sequence of reduction and cyclopropanation 8 - 9, eventually followed by oxidation and an addition to the carbonyl group 9 — 11 — 12, proved most effective. 

Cyclopropan -carbonsaure-anhydrid E5, 638 (aus Saure) Cyclopropan-[Pg.496]

Bicyclo 4.1.0 heptan 7-Chlor-7-(trichlor-ethenyl)- E19b, 742 (Cyclopropen-Ringsp. + En) Cyclopropan 1,1 -Dicyclopropyl-2,2, 3,3-tetrachlor- E19b, 351 (Carben + En)... 

Isopropyliden-l-phenyl- E17a, 344 (Ar —CHN2 + 1,2-Dien) El 9b, 106/113 (Carben + En) Cyclopropan--bicyclo[2.2.1 heptan 3-Ethyliden-2-methylen-E19b, 460 (Ringspaltung) 1,3,5,7,9,11-Dodeeahexaen V/ld, 62... 

Adamantan 1 -Ethyl-2-hydroxy-E 9c, 392 (C-Gerustumlagerung) m-Bicyclo 6.2.0 decan 9,9-Dimethyl-10-oxo- IV/4, 187 E17e, 214 (Keten-imin + En NaOH), 272 (Keton + 1,1 -Br2 — cyclopropan/R — Li A) Bieyclo 3.2.0 heptan 3-tert.-Butyl-1-methyl-6-oxo- E17e, 237 (2-CH2Tos-subst.-cyclohexanon/ NaOH)... 

Although bicyclo[3.1.0]hexane and bicyclo[4.1.0]heptane are modestly efficient electron donors, the main value of these ring systems lies in the rigid framework they offer for the elucidation of the stereochemical course of radical cation reactions. We will mention several vinylcyclopropane systems and several tricycUc cyclopropane derivatives. 

The regiospecific intramolecular capture of the internal cyclopropane bond of the bicyclo[4.1.0]heptane radical cation, 84 +, by the pendant hydroxyalkyl group also amounts to backside substitution of an intramolecular leaving group [217]. 

The intramolecular cyclopropanations of a-diazocarbonyl compounds have been extensively studied and recently reviewed . The reaction is satisfactorily accomplished when the diazo carbon atom is proximal to the double bond in the substrate. Thus, the construction of bicyclo[3.1.0]hexane and bicyclo[4.1.0]heptane skeletons has been achieved by this method, whereas the synthesis of bicyclo[5.1.0]octane or the larger bicyclic systems has usually been difficult (equation 73). Bicyclo[2.1.0]pentan-2-ones expected in the reaction of j8,y-unsaturated diazoketones are generally labile and readily undergo the ring cleavage to give jS,y-unsaturated ketenes. ... 

A ring enlargement involving rupture of a cyclopropane ring on anodic oxidation is exemplified in the transformation of bicyclo[4.1.0]heptane-7-carboxylic acid in methanol to 3-methoxycycloheptene [23]. 

Norbornyldiazomethane (1) was prepared by gentle heating (90-100 °C) of the corresponding tosylhydrazone salt, obtained from bicyclo[2.2.1]heptane-l-carbaldehyde, in a Kugelrohr apparatus. 1-Norbornyldiazomethane (1) is an unstable orange-yellow liquid and was immediately dissolved in a solvent prior to use. Irradiation of a benzene solution of 1-norbor-nyldiazomethane (1) in the presence of ( )- or (Z)-but-2-ene for 2 hours at 25 C led to cyclopropanated products 2 and 3/4 in addition to dimeric products of the precursor carbene. The addition of the monoalkylcarbene is stereospecific with a singlet reaction state. 

The diastereomeric excess could be increased to > 99.5% by employing the bulky chiral auxiliary (3S,55)-2,6-dimethylheptane-3,5-diol which prevents the solvent effect by suppressing the formation of substrate - reagent - solvent complex. The 2,6-dimethylheptane-3,5-diol moiety was readily removed by oxidation with pyridinium chlorochromate followed by treatment with potassium carbonate in methanol to give the bridged cyclopropanol compound. An example is the cyclopropanation of 56 to give predominantly 57 with > 95% de 57 was converted to (15,65 )-bicyclo[4.1.0]heptan-l-ol. ... 

The zinc metal in the Simmons-Smith reaction was replaced by samarium for the cyclopropanation of allylic alcohols with chloroiodomethane. High yields of cyclopropanes, often with high diastereoselectivities, were obtained using samarium amalgam/diiodomethane. Cyclo-hex-2-enol (115a) gave exclusively s y -bicyclo[4.1.0]heptan-2-ol (116a), no traces of the anti-... 

In refluxing cyclooctene, exo-7-bromo-c t/f>-7-(trimethyistannyl)bicyclo[4.1.0]heptane (20) reacted via the corresponding cyclopropylidene intermediate to afford spiro[bicyclo[4.1.0]hep-tane-7,9 -bicyclo[6.1.0]nonane] (21) in 76% yield. However, this reaction is not preparatively interesting and not applicable to a-bromo-a-(trimethylstannyl)cyclopropanes in general, because the cyclopropylidenes from the latter gave ring-opened allenic products. ... 

Obtained from active methylene compounds, such as malonic esters, -0x0 esters and jS-oxo sulfones, iodonium ylides serve as precursors of the corresponding carbenes. Their decomposition by a catalytic amount of a copper salt in the presence of a C-C double bond has been used for inter- and intramolecular cyclopropanation reactions. Thus, reaction of cyclohexene with bis(methoxycarbonyl)methylene(phenyl)iodine(III) under the catalytic action of bis(acetylacetonato)copper(II) yielded dimethyl bicyclo[4.1.0]heptane-7,7-dicarboxylate (1) (38%, mp 91-93°C) in addition to tetrakis(methoxycarbonyl)ethene (41%). ... 

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