Vinylcyclopropanes intramolecular cycloaddition

Scheme 16.75 Rh-catalyzed intramolecular [5 + 2]-cycloadditions of allenes and vinylcyclopropanes.

The [Rh(NHC)Cl(COD)]/AgSbF6-catalysed intramolecular 4 + 2-cycloaddition of dienynes and the intramolecular 5 + 2-cycloaddition of alkyne vinylcyclopropanes formed the corresponding bicyclic cycloadducts in 91-99% yields within 10 min.8... 

As a related reaction, the bicyclo[5.3.0]decane derivative 64 was obtained at 30 °C by the Rh-catalysed intramolecular [5+2] cycloaddition of the alkyne with the vinylcyclopropane moiety in 61. The latter behaves as a pseudo-1,3-diene in oxidative addition, and generates 62. This is followed by rearrangement to 63, whose reductive elimination gives 64 [20]. [Rh(CO)2Cl]2 is a better catalyst than RhCUPl+P. The reaction can be extended to alkenes [20a],... 

When the double bond of the enyne possesses a cyclopropyl substituent, an intramolecular [5+2] cycloaddition of alkyne and vinylcyclopropane takes place [75, 76]. The ruthenacycle does not undergo /l-hydride elimination but a rearrangement of the cyclopropane to produce a ruthenacyclooctadiene. Thus, a variety of bicyclic and tricyclic cycloheptadienes were obtained in good yields [75] (Eq. 55). 

In a study of vinylcyclopropanes with tetranitromethane (TNM), from 1,1-divinylcyclopropane 156, a specific 1,4-diene, the unexpected product 118, was obtained. The formation of the nitronic ester was accompanied by homo-allylic rearrangement, followed by the intramolecular 1,3-dipolar cycloaddition (Equation 9) <2002DOC9>. 

JCycloadditions. Both intermolecular and intramolecular versions of the cycloaddition involving a vinylcyclopropane and an alkyne have been developed. The Rh-catalyzed reaction is very valuable for rapid assembly of unsaturated seven-membered... 

Unlike reactions with alkenes and alkynes, relatively few examples of intramolecular transition metal-cataly2ed reactions of allenes have been reported so far. Continuing our endeavor to extend the synthetic reach of transition-metal-catalyzed reactions, we have directed our attention at the use of an allene as the n-system. As with the alkene systems, two stereochemical outcomes are possible for the intramolecular [5+2] cycloaddition of allene-vinylcyclopropanes. The use of an allene moiety also presents an interesting opportunity to incorporate chirality into the substrate. Additionally, because ene-vinylcy-clopropane substrates substituted at the alkene terminus are not amenable to [5+2] cycloaddition, the use of an allene allows access to the same framework that would be obtained by cycloaddition of terminally substituted alkene substrates, thereby circumventing one of the few limitations encountered with ene-vinylcyclopropane cycloadditions. 

The photocycloadditions of 2,3-dimethyl-l,3-diene with 4-(alk-l-ynyl)-substituted coumarins (5) produced a mixture of 4 + 2- and 4 + 4-cycloadducts (6) and (7), respectively. However, the corresponding thiocoumarins (8) yielded a single 4 + 2-cycloadduct (9) (Scheme 2)." The intramolecular photocycloadditions (>290nm) of 1,3-enynes with 2-pyridone yielded 2 + 2- and 4 + 4-cycloadducts. The Rh(I)-catalysed formal 5+l-/2 + 2 + 2-cycloaddition of 1-yne-vinylcyclopropanes (10) with two carbon monoxide units produced multifunctional angular tricyclic 5/5/6 compounds (11) in a one-step mechanism (Scheme 3). ... 

Later, Hayashi extended the scope of rhodium-catalyzed asymmetric intramolecular [5+2] cycloaddition to alkynyl-vinylcyclopropanes (Scheme 28) [68],... 

Wender s group has also developed rhodium-catalyzed intermolecular [5-1-2] cycloadditions. At first, they found the catalysis system of Rh(PPh3)3Cl for the intramolecular reactions was not effective at all for the intermolecular reactions. To effect the intermolecular [5-1-2] cycloadditions, [Rh(CO)2Cl]2 must be used and oxygen substitution of the cyclopropane was necessary (see (17)) [37-39]. Then they successfully expanded the substrate to unactivated vinylcyclopropanes by adjusting the substituents. For monosubstituted alkynes, the substitution on the olefin terminus directs the formation of single isomer that minimized steric hindrance (see (18)) [40]. The [5-1-2] cycloadditions can also be applied to VCPs with allenes (see (19)) [41]. It should be noted that the alkyne substituent did not interfere with the reaction, indicating that allenes as reaction partners were superior to alkyne in the [5-1-2] cycloadditions. Curiously, the authors didn t report the corresponding intermolecular [5-1-2] cycloadditions of VCPs with alkenes. 

Trost et al. reported the first asymmetric total synthesis of pseudolaric acid B by exploiting a rhodium-catalyzed intramolecular [5-1-2] cycloaddition reaction of a vinylcyclopropane with an alkyne (Scheme 8.2) [4]. The vinylcyclopropane having a tethered alkyne moiety 12 was synthesized from chiral precursors 9 and 11. Treatment of 12 with a cationic rhodium(1) catalyst promoted the [5-1-2] cycloaddition reaction to form a [5.3.0]bicyclic skeleton of 13 in a diastereoselective fashion. A few steps of functional group transformations provided the alkoxycarbonyl... 

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