Regio- and stereo-specificity in the cyclisation of medium ring 1,5-dienes

Biogenetic-Type Rearrangements of Terpenes

“…Electrophiles effect regiospecific addition to the 1,2-double bond and stereospecific cyclization to trans-decalins, transformations closely parallel to the biogenesis ofthe eudesmanes (1 23). Similar cyclizations have been observed with numerous oxygenated germacrane derivatives (121 The regiospecificity of these cyclizations may be attributed to Markovnikov participation of the 5,6-double bond in the transition state for Markovnikov protonation of the 1,2-double bond and charge delocalization onto the 5 position. Protonation at the other double bond is less favorable since a Markovnikov orientation would require bonding between carbons 2 and 5 and consequent increase in strain energy.…”

“…The observation that trans-cyclodecene is completely inert to these reaction conditions attests to the transannular interaction between the double bonds in the dienes. Another stereochemical characteristic of these cyclizations is the equatorial disposition of both the entering electrophile and nucleophile, as expected for overallanti addition to both double bonds (121)(122)(123). The anti mode of addition appears to be followed in the initial electrophilic attack in all cases.…”

Structure of (cis,trans,cis-η-1,5,9-cyclotridecatriene)nitratosilver(I)

“…We may also point out that the Ag-[C(5),C(6)] length is the longest, while the C(5)=C(6) bond which is the sole trans-type, is the shortest double bond (Table 3) (Figs. 1 and 2) in the definition of Sutherland (1974). There is a small torsion of the double bonds: only 4 ° for the trans configurated C(5)=C(6) and 3 and 5 ° respectively for the cis C(1)--C(2) and C(9)=C (10) bonds.…”

endo,endo-5,9-Dibromo-cis-transoid-cis-13-oxatricyclo[8.2.1.02,6]tridecane

“…Introduction. Studies in recent years have established that transannular reactions, which are characteristic for electrophilic addition reactions to unsaturated mediumsized cyclic hydrocarbons (Sutherland, 1974;Haufe & Mfihlstiidt, 1979), are not restricted to eight-to eleven-membered compounds, but can also occur in larger rings. Transannular O-heterocyclization occurs when the methoxybromination procedure is applied to twelve-and thirteen-membered 1,5-dienes or 1,5,9-trienes (Haufe & Mfihlst~idt, 1984;Trauer, 1985;Haufe, 1987), whereas tyansannular 7r-cyclizations are the main processes for nine-to eleven-membered 1,5-dienes under similar conditions (Haufe & Miihlst~idt, 1979).…”