Cyclopropane, divinyl

Baden JM, Kelley M, Mazze Rl, et al. 1979. Mutagenicity of inhalation anaesthetics Trichloroethylene, divinyl ether, nitrous oxide, and cyclopropane. Br J Anaesth 51 417-421. 

The Davies group has described several examples of a rhodium-catalyzed decomposition of a diazo-compound followed by a [2+1] cycloaddition to give divinyl cyclopropanes, which then can undergo a Cope rearrangement. Reaction of the pyrrol derivative 6/2-51 and the diazo compound 6/2-52 led to the tropane nucleus 6/2-54 via the cyclopropane derivative 6/2-53 (Scheme 6/2.11) [201]. Using (S)-lactate and (R)-pari lolaclorie as chiral auxiliaries at the diazo compound, a diastereoselectivity of around 90 10 could be achieved in both cases. 

The photoindueed 1,7-cycloaddition of carbon monoxide across the divinyl-cyclopropane derivative 32 yields the two cyclic dienyl ketones 34, via the ferracyclononadiene intermediate 33 [18]. (Scheme 11) cyclopentene rearrangement. The dienylcyclopropane 35 is capable of forming the complex 36, followed by ring enlargement to 37 [19]. 1,1-Dicyclopropylethylene 29 is also converted to the 1-cyclopropyl-1-cyclopentene 38. The additional functionality of vinylcyclopropanes is necessary to serve as a 7t-donor... 

It should be noted that products like 443 and 447 are the normal products of photochemical reactions of acyclic 1,3,5-hexatrienes, as well as of divinyl aromatics, but are quite unusual for thermal transformations of such substrates. Presumably, the electrostatic repulsion between CF2 groups prevents the formation of conformation 450 which is necessary for the electrocyclic ring closure (i.e. 438 — 439 and 445 -> 446). Instead, it leads to conformation 451 which is favorable to generate the diradical and then the fused vinyl-cyclopropane intermediates 452 (equation 170). Note that the rearrangement 452 —> 453... 

Another product, which may be the cis-iraws-cyclo-octadiene, is also formed in a small-percentage yield). This is exactly analogous to the transition complex postulated for the isomerization of ci 1,2-divinyl-cyclopropane. 

Figure 12.6. a) Cope rearrangement of 1,5-hexadiene (6) oxy-Cope rearrangement (c) divinyl-cyclopropane rearrangement (d) degenerate rearrangements of bullvalene. 

Two unique ring enlargements which can also be classified as divinyl-cyclopropane-cycloheptadiene expansions are shown in equations 177 and 178 ". The last reaction has been employed for constructing the l,6-methano[10]annulene carbon skeleton required for the unusual furanosesquiterpene dihydrospiniferin-1. ... 

The intramolecular reaction of the carbene from diazo ester 280, which contains a 1,3-diene moiety in the ester group and a double bond adjacent to the carbene center, leads to the formation of a substituted 1,2-divinyl-cyclopropane, whose CIS isomer then undergoes a Cope rearrangement to give substituted cycloheptadiene. In such a way, bicyclic 281 and tricyclic 282 y-lactones with a neighboring seven-membered carbocycle have been obtained (89JOC930). 

AryI-2-vinylcyclopropanes 21 undergo both vinylcyclopropane to cyclopentene and divinyl-cyclopropane to benzocycloheptene rearrangements competitively (see also Section 2.4.5.) at temperatures in the range of 150-200°C. ... 

The mechanism of the thermal and photochemical rearrangement is believed to proceed as shown (1 - 2), with the dilemma of concerted vs. diradical nature not definitely resolved for all cases. A comparison of energy parameters for the thermolysis of the parent 1,2-divinyl-cyclopropane and of l-(hex-l-enyl)-2-vinylcyclopropane ( - and Z-isomers, tram- and cis-cyclopropanes) has been reported. When both alkenes bear a Z-positioned substituent, the rearrangement of the divinylcyclopropane system becomes very slow and other processes, such as the [1,5] sigmatropic shift of alkyl(vinyl)cyclopropanes or the vinylcyclopropane to cyclo-pentene rearrangement, may compete (see also Section 2.4.3.). Both the mechanism and the applications of this rearrangement have been reviewed. 

A solution of the appropriate jS-iodo enone 42 or 46 (1 mmol) in dry THF (2 mL) was added to a clear yellow EtjO soln of the cuprate reagent, cooled to — 78 C, which was prepared from l-bromo-2-vinyl-cyclopropane cisitrans ca. 7 3, 1.5 mmol) phenylsulfanylcopper (1.5 mmol), and r-BuLi (3 mmol). The resultant mixture was stirred at — 78 °C for 1 h, at — 20 C for 1 h, and at O C for 1 h (R = H) or 2h (R = Me). During this time the color of the mixture changed from yellow to brown. MeOH (1 mL) and EtjO (10 mL) were added and the suspension thus obtained was filtered through a short column of silica gel (ca. 10 g). The column was eluted with EtjO (200 mL) and the combined eluate was concentrated under reduced pressure. Distillation (ca. 60-90 °C/ca. 0.5 Torr) of the residual material provided the divinyl-cyclopropane (43 or 47) as a clear, colorless oil which was subjected to thermolysis (neat, 180 °C, 30 -45 min) under an atmosphere of N. Distillation of the thermolysate provided suitably pure annulated cyclohep-tadienes 44, 45 or 48. In those cases where the product was accompanied by small amounts of unidentified impurities, a pure sample of the desired annulation product was collected by preparative GC. 

The synthesis of bicyclo[3.2.1]octadienes 86 has been accomplished by refluxing divinyl-cyclopropanes 85 in xylene. Subsequent research led to the development of conditions employing a rhodium-catalyzed step for the synthesis of bridged systems via the cyclopropanation of cyclopentadienes, furans and pyrroles (see section on transition-metal-mediated rearrangements). 

Transition metal (Cr, Mo) carbene complexes, e.g. 28, 30, 32, participate in additions to dienes and diene-tethered acetylenes with concomittant generation of divinyl-cyclopropanes, which undergo ring expansion under the reaction conditions to cycloheptadiene-annulated ring systems such as 29, 31 and 33. 

Bicyclo 4.1.0]hept-2-enc 7-Chloro- 1449 Bicyclol2.2. l hept-2-ene 5-Chloro- 1959, 2454 Bi-cyclopropylidene 2-Chloro-2-methyl- 551 Cyclopropane l-(4-Chloro-butynyl)- 45 l-ChIoro-l,2-divinyl- 581 C HjCIFNO Pyrrolidine... 

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