Rearrangements of pinane derivatives. Part 9. 8,8-Dimethyltricyclo[5.1.1.0^2,5]nonan-2β-ol, a tricyclic pinane derivative

Abstract

Acetolysis of the toluene-p-sulphonate ester of 2-(2-hydroxyethyl) -6,6-dimethylbicyclo[3.1.13 hept-2-ene (nopol) (1; R = OH) gave a good yield of the acetate of the previously unknown tricyclic pinane derivative 8,8-dimethyltricyclo[5.1.1 .02*5] nonan-2P-01 (4a). This molecule has a bridgehead hydroxy group, and so is remarkably stable to acids, despite being highly strained from having two cyclobutane rings. However, the hydroxy group is adjacent to the new cyclobutane ring, so that (4a) is readily oxidised to the gcetate of the hydroxytetrahydrofuran, 2phydroxy-8,8-dimethyl-l O-oxatricyclo-15.1.1 -1 29s]decane (5; R = OAc). Hydrolysis of the acetate group, followed by oxidation of the alcohol (5; R = OH), yields 8,8-dimethylbicyclo[5.1.1] nonane-2,5-dione (6). The base-catalysed dehydration of 2-(2-hydroxyethyl)-6,6dimethylbicyclo[3.1.l]hept-2-ene (nopol) (1; R = OH) yields a mixture of the dienes (2) and (3), but the reaction does not yield any tricyclic pinane derivatives., The Clarke-Eschweiler cyclisation has been demonstrated3 to take place with 2-(2-aminoethyl)-6,6-dimethylbicyclo[3.l.l]hept-2-ene (nopyl- amine) (1; R = NH,), but does not yield a system with a pinane skeleton; rearrangement gives products based on the fenchyl and terpinyl systems. The only reported tricyclic pinane derivative is 1 O,lO-dimethyltricyclo~7.1. 1.02*7]undec-2( 7)-en-6-one, prepared from P-pinene during the synthesis of P-~elinene.~ In this case, a second six-membered ring was added to the pinane skeleton. This suggested that a pinane with two cyclobutane rings may well exist, but could be highly labile, and thus isolable only under mild conditions. We attempted to prepare it by the solvolysis of the toluene-p-sulphonate of nopol. Results and DiscussionThe toluene-p-sulphonate of nopol (1; R = OH) was prepared by conventional methods. It readily underwent solvolysis in

Preparation of Campholenal Analogues: Chirons for the lipophilic moiety of sandalwood‐like odorant alcohols

“…Aldehyde (+)-4o, finally, was obtained from (-)-20 [44] (59% yield) and represents, with (+)-4f (and (+)-4c), a potential homologue of (+)-4b, after appropriate transformations. Epoxidation of iodide (-)-7a resulted in the formation of a mixture of (-)-2g (22%), (-)-3g (20%), and (+)-12 (44%, Scheme 3 ) [45]. Finally, aldehyde (+)-13 [46], with an exocyclic C=C bond, was obtained selectively in 71 YO yield from (+)-4f by a thermal retuo-Prins reaction (Scheme 4 ) .…”

The mechanism of formation of 8,8-dimethyl[4.2.1.03,7]nonan-6-yl acetate (fortesyl acetate) during acetolysis of nopyl toluene-p-sulfonate

“…The other product observed during acetolysis of nopyl toluene-p-sulfonate is 1-ethyl-4-(2-propyl)benzene (26), probably arising as a result of breaking the gem-dimethyl bridge. 1 This contrasts with the observation 20,21 that the parent hydrocarbon of 2 (brendane, 27) can be converted easily into noradamantane 28. Calculation of the enthalpies of formation of these molecules confirms that such rearrangement is energetically favourable.…”

“…It was converted into its toluene-p-sulfonate ester by conventional methods 1 and was subjected to acetolysis in acetic acid as described earlier. 1 The product was distilled to yield fortesyl unlabelled fortesol was absent in this labelled material. The 1 H NMR spectrum showed that a multiplet at δ 1.88 corresponding to the equatorial hydrogen on C-4 was absent.…”

“…Acetolysis of [11, H 2 ]-2- (6,6-dimethylbicyclo[3.1.1]hept-2en-2-yl)ethyl toluene-p-sulfonate 24 was carried out by refluxing the ester (4 g) at 118 ЊC for 100 h in acetic acid (50 mL), containing sodium acetate (1.3 g). 1 The cooled solution was poured into water (50 mL) and extracted with diethyl ether (3 × 20 mL). The combined extracts were washed with water, aqueous sodium hydrogen carbonate and water again before being dried (MgSO 4 ).…”

Monoterpenoids

“…The conformations of a number of halohydrins derived from (+)-car-3-ene (231) have been studied using IR spectroscopy.255 Diels-Alder reaction of isoprene with (a-1 -tributylstannylbut-1-en-3-one yields the adduct (234), which can be converted into (-t)-car-3-ene (231) on its treatment with MeLi followed by SOC12-pyridine.248 (+)-Car-2-ene (233) has been used as starting material in a synthesis of the cembranoid ( + ) -~a s b e n e , ~~~ and (-))-trans-caran-2-one (235) can be converted into the useful guiane synthon (+ ) - (236). 134 A reactor for the large-scale homogeneous catalytic autoxidation of (+)-car-3-ene (231) has been described.…”