Bicyclic alcohol

Secondary bicyclic alcohols are quantitatively oxidized by Jones reagent however rearranged products are obtamed [5f ] (equation 47)... 

Guaiol is a tertiary bicyclic alcohol, with one double linkage, having the following characters —... 

The reaction of the enamines of cyclohexanones with a,ft-unsaluraled sulfones gives mixtures resulting from attack of the enamine at the a- and /(-carbons of the oc,/ -unsaturated sulfone. The ratio of x- and /1-adducts is dependent upon the reaction solvent, the geometry and structure of the sulfone1 4. The diastereoselectivity of these reactions is also poor. The reaction of lithium enolates of cyclic ketones with ( )-[2-(methylsulfonyl)ethenyl]benzene, however, gives bicyclic alcohols, as single diastereomers, that result from initial -attack on the oc,/ -unsaturated sulfone5. 

The following syntheses of five-membered carbocyclic systems involve radical-induced epoxide fragmentation with radical translocation and cyclization. The resulting bicyclic alcohols are formed as a mixture of two epimeric esters with cw-fused rings.[71]... 

This hypoiodite reaction can also be used for ring expansion of cyclic ketones.2 Thus Barbier cyclization of a-(w-iodopropyl)cyclododecanone (3) furnishes the bicyclic alcohol 4, which undergoes regioselective cleavage to a 15-membered iodo... 

Fig. 55 Stereoselective twofold cyclization of unconjugated dienones to bicyclic alcohols [303].

C—H insertion reaction occurs in a stereoselective manner. Various attempts based on chiral lithium amide bases gave only moderate enantioselectivities. More efficiently, the reaction is carried out by means of s-butyl- or wo-propy 1-lithium in the presence of (—)-sparteine under these conditions, the bicyclic alcohol 92 was obtained in 74% yield and 83% ee. This concept has been extended to various meio-epoxides, an example of which is shown in equation 52. ... 

Neutral hydrolysis of e, (/u-tricyclo[4.1.0.03-7]hcpt-3-yl 4-methoxybenzoate15 or 4-nitroben-zoatc16 in 90% aqueous acetone at room temperature gave some unreacted rearrangement product besides the bicyclic alcohol. 

Bicyclic alcohols with angular methyl groups (11, 10-11). The reaction of 2,5-dimethylmethylenecyclopentane (1) with acrolein (1 equiv.) and (CH3)2A1C1 involves two sequential ene reactions to give the expected bicyclic alcohol 2 (69%) and in addition the corresponding ketone 3 (12% yield), even in the absence of an oxidant.6 In the presence of 2 equiv. of acrolein, the reaction results in 3 in 60% yield and only 1% of 2. Apparently, the alkoxide precursor to 2 undergoes... 

IntramolecularBarbier-type cyclization (12,429-430).1 Cyclizations of 2-(co-iodoalkyl)cyclopentanones induced with Sml2 result almost entirely in cw-fused products (equation I). ds-Fused bicyclic alcohols are also formed selectively from 2-substituted 2-(co-iodoalkyl)cycloalkanones (equation II). 

The basis of the 7-hydrogen transfer lies in the proximity of such hydrogens to the reactive carbonyl group. If by virtue of structure other hydrogens are closer to the excited carbonyl group, they will be transferred to the carbonyl group. An example of such an effect is found in the photochemical rearrangement of cyclodecanone (Formula 257) to the bicyclic alcohols [Formulas 258 (42%) and 259 (10%)] (108,109). Cyclo-... 

Fischli, Branca, and Daly (97) have reported that epoxysulfone 346 gave stereospecifically the bicyclic alcohol 347 upon treatment with sodium amide in refluxing toluene. Treatment of 347 with potassium t -butoxide gave the enlarged ring ketone 348 (for a similar fragmentation, see ref. 98). 

A slightly modified procedure - oxidation with 100 per cent excess of chromic acid at 0 °C for a short period - is adopted for strained bicyclic alcohols (e.g. the oxidation of ( —)-borneol to ( —)-camphor, Expt 5.87) and gives excellent yields of the corresponding ketones. Cycle ketones which are susceptible to acid-catalysed epimerisation are moreover obtained by this procedure in a high degree of epimeric purity. 

Cyclohexanol annelation,8 In the presence of dimethylaluminum chloride, a,/3-unsaturated aldehydes or ketones undergo two consecutive ene reactions with alkylidenecycloalkanes to form bicyclic alcohols. Thus, if the reaction of methylene-cyclohexane and methyl vinyl ketone is conducted at — 20°, the product (I) of the initial ene reaction can be isolated in 39% yield together with traces of 2, which becomes the main product from reactions conducted at 25°. The intermediate is usually not isolable in reactions of a,/l-enals. Thus, reaction of ethylidenecyclopentane and acrolein at 0° gives 3 in 72% yield. An attractive feature of this annelation is that... 

Laqua, H. Frohlich, R. Wibbeling, B. Hoppe, D. Synthesis of enantioenriched indene-de-rived bicyclic alcohols and tricyclic cyclopropanes via (-)-sparteine-mediated lithiation of a racemic precursor and kinetic resolution during the cyclocarbolithiation. J. Organomet. Chem. 2001, 624, 96-104. 

Upon employing the more rigorous simultaneous distillation-extraction (SDE) technique (100°C pH 3.7) to isolate the quince fruit volatiles, the resulting aroma composition distinctly differed from that obtained by HVD/SE. After SDE the hydrocarbon 5, the bicyclic alcohol 6 and 3,4-didehydro-(B-ionol (7) were identified as... 

In a further series of experiments, model reactions to thermally-degrade 3-hydroxy-(5-ionol (9) were carried out. The results of these studies are represented in Figure 4. In these model reactions, compounds 5, 6 and 7 as well as unidentified isomers of 5 and 6 were all found in amounts very similar to the natural quince flavor composition obtained by SDE conditions. However, as shown in Figure 4, additional products were found comprising the megastigmatrienols 13, 14 and the tentatively-assigned bicyclic alcohol 15. These latter compounds were not detectable in quince fruit juice. Thus, the diol 9 came under question as a possible precursor. 

As a reductive cascade reaction with Sml2, treatment of methylenecyclopropyl ketone (310) with Sml2 in a mixture of HMPA and f-BuOH at 0 °C generates bicyclic alcohols (311a) and (311b) which are the skeleton of a natural product, paeonilactone, as shown in eq. 3.130. 

In 2007, Molander demonstrated that 5-exo-transannular reductive carbonyl addition to an endo- or exocyclic alkene can be highly effective for the formation of bicyclic ring systems. For example, treatment of cyclooctenone 36 with Sml2 and HMPA gave bicyclic alcohol 37 in 70% yield (Scheme 5.28).56 Transannular cyclisations have even been extended to 11-membered carbo-cyclic starting materials and give bicyclic products in good yield. 

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