Bicyclic Systems Containing Cyclopropane Rings

Bicyclic Systems Containing Cyclopropane Rings A. Bicyclobutane 

The recent syntheses of this compound have made it available for thermal studies (Wiberg and Lampman, 1963 Frey and Stevens, 1964 Srinivasan, 1963). Above 190° C, bicyclobutane isomerizes to butadiene. The reaction is predominantly homogeneous but there is some evidence for a small heterogeneous component of the reaction. The results of Srinivasan et al. (1965) yield the Arrhenius equation 

Chesick (1964) has reported the thermal isomerization of this compound for which there are now thermochemical data (Turner et al., 1965). The only product was 2,3-dimethylbutadiene. Once again the results suggest a concerted process for the reaction. Above 260° the reaction appears to be entirely homogeneous, and using these data one obtains 

The thermal isomerization of this compound was first studied in detail by Halberstadt and Chesick (1962) in the temperature range 288-310° C and in the pressure range 67 to 0-04 mm, and was found to be homogeneous and kinetically first order. Cyclopentene was the major product ( 99 %) and the high-pressure Arrhenius equation obtained was 

Steel et al. (1964) reject these arguments and do not consider that the reaction path represented by equation (II) can be eliminated indeed they favour this scheme. Their own work on this isomerization, carried out over a somewhat wider temperature range, yielded the Arrhenius equation for the formation of cyclopentene 

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VI. Bicyclic Systems Containing Cyclopropane Rings A. Bicyclobutane... 

Fused bicyclic systems, containing a substituted five-membered ring, can be conveniently prepared by the reactions of the magnesium complexes of 1,2-dimethylene-cycloalkanes with carboxylic esters. This reaction proceeds by a magnesium salt of a spiroenol that contains a cyclopropane ring. Quenching of the intermediate at an appropriate temperature creates an alternative pathway for the reaction, leading to a... 

Recently, a catalytic system consisting of a second generation Grubbs catalyst or an in situ non-carbenic ruthenium complex have allowed a cascade catalytic reaction of cyclopropanation/ring closing metathesis of dienynes containing a malonate or bissulfone moiety. In this reaction, the interaction between the triple bond and one double bond gives a bicyclic product via cyclopropanation, and then the subsequent diene RCM produces the last cyclization step [16] (Scheme 6). 

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