Octane structure

Thus, the predictions seem to be in conflict with the observed syn biases. However, along the trajectory of attack of the nucleophile to the carbonyl group of the bicyclo[2.2.2]octane structures (indicated in 23 and 24), out-of-phase interactions between the reagent and the substrate are involved, and this is different from the situation in the bicyclo[2.2.1]heptane structures (15a) [83-87]. Thus, attack on the side opposite to the unsaturated moiety will be favored. This is a kind of SOI (Fig. 3a) which unsymmetrizes the n face. 

Carboxylic acids can also be protected as orthoesters. Orthoesters derived from simple alcohols are very easily hydrolyzed, and the 4-methyl-2,6,7-trioxabicyclo[2.2.2]octane structure is a more useful orthoester protecting group. These... 

A preliminary report of another Te82+ in a cage-like bicyclo[2.2.2]octane structure appeared in 1997.4 This structure is best understood as a Zintl structure in which the two bridgehead Te atoms bear the positive charge and three noncharged Te2 bridges are formed. However, no full structural report on this compound has been published and therefore we resist further analysis. 

Fundamentally, D-glucofuranurono-6,3-lactone (4) contains the 2,6-dioxabicyclo[3.3.0]octane structure (5), just as do ido-, manno-, and... 

An asymmetric total synthesis of (—)-secodaphniphylline was carried out using a mixed Claisen condensation between (—)-methyl homosecodaphniphyllate (11) and a carboxylic acid derivative 154 with the characteristic 2,8-dioxabicyclo[3.2.1]octane structure commonly found in the daphniphyllum alkaloids (Scheme 18.23) [68,69]. The necessary chirality was secured by an asymmetric Michael addition reaction of... 

Teg + has several isomeric forms. The cation commonly shows the same structure as 8g + and 8eg + (see Figure 12(a)), but the transannular interaction seems to be stronger in tellurium than in sulfur or selenium. An even more pronounced bicyclic nature is found in the Teg + cation in Te8[WCl6] (see Fignre 12(b)). The ttansannular bond is only 2.993 A. In addition, Teg + has other isomers. It has been found to show a bicycyclo[2,2,2]octane structure ... 

However, if the norbornyl carbonium is brought to the proper temperature, passage to the more stable bicyclo[3.2.1]octane structure becomes possible. Lack of evidence for the reverse passage points to the lack of thermodynamic stability of the norbornyl structure even at low temperatures. 

The evolution of the systems with increasing temperature or reaction time indicates that bicyclo[3.2.1]octane structures, rather stable in the medium range of temperatures (160-200°) are irreversibly converted to bicyclo[3.3.0]octane isomers at higher temperatures (250°). They act as unstable intermediates whenever a temperature higher than 200° is required to pass from the bicyclo[2.2.1]heptane to the bicyclo[3.2.1]-octane, and this happens in the Gg and Cio series. 

The passage from bicyclo[2.2.2]octane structures to the isomeric bicyclo[3.2.1]octanes is irreversible for all practical purposes in the CsHiz and C9H14 series (it was not investigated in the CioHie series) and this conclusion is substantiated by other facts the acid-catalyzed dehydration of 2-methylbicyclo[3.2.1]-2-octanols and 3-methylbicyclo-[3.2.1]-3-octanols gives small quantities of methylbicyclo[2.2.2]octenes 30), while the acid-catalyzed hydration of bicyclo[2.2.2]-2-octene forms the bicyclo[3.2.1]-2-octanol 27) the nitrous acid deamination of 2-aminobicyclo[2.2.2]-5-octene goes to bicyclo[3.2.1]octenols 31) and the solvolysis of bicyclo[2.2.2]-5-octen-2-ol esters to bicyclo[3.2.1]octenols 32). 

Dioxene and 3,4-dihydro-2//-pyran have been reported to afford (2 + 2)-cycloadducts (20) via addition to the carbon-sulfur double bond of hexafluorothioacetone at —78°.47 Although no conclusive evidence has been given, the 2-oxa-8-thiabicyclo[4.2.0]octane structure (20b) was preferred to others on the basis of mass spectrometric data.47... 

Plants in the Solanaceae family produce a variety of alkaloids, some of them having a considerable therapeutic importance. One such group of alkaloids possesses a tropane nucleus. Tropane alkaloids are structurally related natural products having in common the azabicyclo[3.2.1]octane structure and therefore the systematic name for tropane is 8-methyl-8 azabicyclo[3.2.1]octane (Fig. 1). The majority of these alkaloids are esters between organic acids and hydroxytropanes. 3a-Hydroxytropane, called tropine, is the amino alcohol most frequently encountered. In addition, its 3 (3-isomer (pseudotropine), the di- (3,6- 3,7- or 6,7-) and trihydroxylated... 

Another interesting point is the low coproduction of impurities. Nevertheless we observed the formation of small amounts of low boiling points products (Xi.Xj) compared with IPDA. After analytical characterisation we assigned to the most important of them the azabicyclic (1,3,3-trimethyl-6-azabicyclo[3,2,1]octane) structure. In anhydrous conditions as in our case, byproduction of aminoalcohol is minimized. On the other hand, when water is present the proportion of aminoalcohol increases. These observations can be explained by the following mechanism. 

Solvolyses of 8-X-3,4-tetrafluorobenzobicyclo[3,2,l]-octadienes and -octenes (X = leaving group) have been reported the syn-epimers react with retention of the skeleton and stereochemistry at C-8 by way of the non-classical carbonium ion intermediate, whereas the anti-compounds yield products with the benzobicyclo-[3,3,0]octane structure, presumably by a classical ion pathway. Although the epimeric tosylates (124) and (125) are solvolysed at different states and show different sensitivities to solvent variation, they produce the same product mixture, comprising... 

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