Decalin-1,8-diones

Reductions of symmetrical bicyclic diketones may also be effected selectively, as illustrated in Scheme 12. The stereospecificities of the HLADH-catalyzed transformations of the unsaturated decalin-diones (25) and (27) to the corresponding hydroxy ketones (26) and (28), and in fact all specificity aspects of this enzyme, are fully predictable using a simple to use, cubic-space model of the enzyme s... 

With this idea in mind, Deslongchamps treated the cw-decalin-2,7-dione (12) with a mixture of acetic anhydride-acetic acid in the presence of boron trifluoride ethyl etherate, at room temperature, and the twistanone 20 was isolated in 75% yield. The whole synthetic sequence is outlined in Scheme 13.1.7. 

Copper-catalyzed tosylaziridinations with Phi = NTs have also been incorporated into multistep syntheses of a-vinylalanine [185], and the trans-decalin core of the marine alkaloid, kalihinol A [186]. Distereoselective tosylaziridinations of planar-chiral azoninones [187], and Ses-, nosyl-, and tosylaziridinations of 11-pregnene -3,20-dione have also been reported [188,189]. 

Two-phase oxidation. A simple procedure for the oxidation of a secondary alcohol to a ketone consists in adding a cold solution of sodium dichromate and sulfuric acid containing a little acetic acid to a stirred solution or suspension of the alcohol in benzene while cooling to 1-6°. Since the ketone as formed is distributed into the benzene layer and protected against secondary reactions, sensitive ketones can be isolated in high yield without appreciable inversion at adjacent centers of asymmetry. Thus a cis-trans mixture of 1,5-dihydroxydecalins affords a cis-trans mixture of decalin-l,5-diones in 71-76% yield in the two-phase system the cis isomer present is not converted into the more stable trans diketone. 

Johnson et al. ° prepared rra s-decalin-l,4-dione by hydrogenation of 1,4-naphthoquinone over RUO2, followed by chromic acid oxidation of the resulting diol and isomerization of the cis- to the rrnn.v-dione. 

In a very similar manner, tandem 1,6- and 1,4-additions of -dicarbonyl compounds to methyl 2,4-pentadienoate were utilized by Danishefsky and coworkers- foi the formation of several bi- and tricyclic ring systems. For example, reaction of the enolate of dimedone with this ester gave the expected 1,6-addition product protonation/deprotonation set the stage for a subsequent intramolecular 1,4-addition (equation 9). Likewise, a ketodiester was used to transform the pentadienoate in a one-pot procedure by consecutive 1,6- and 1,4-additions into a richly functionalized tricyclic product which was then converted into the natural product ( )-cpiclovane (equation 10). According to this principle, Irie and coworkers obtained several decalin-2,7-diones by treatment of 2-methylen-2-cyclohexenones with dimethyl 3-oxoglutarate. 

Intramolecular acylation. This reaction is the key step in a new synthesis of the twistane ring system By a Canadian group.14 The starting material, decalin-2,7-dione (3), can be prepared easily in quantity by hydrogenation of 2,7-dihydroxynaphthalene to a mixture of isomeric diols (2) and chromic acid oxidation of the mixture.15 16 Treat-... 

Decalin-l,8-diones. Trimethyl propane-1,1,3-tricarboxylate and cyclohex-l-en-3-one added to a soln. of Mg in hot abs. methanol, refluxed 1 hr., the solvent removed by distillation, abs. benzene added repeatedly if necessary and benzene distilled until the b.p. of the distillate reaches 79° dimethyl decalin-l,8-dione-4,4-dicarboxylate. Y 15% based on startg. ester consumed. K. Schank and N. Moell, B. 102, 71 (1969). 

Li added to a mixture of 10-propargyl-frans-decalin-2,7-dione with liq. NHg-ether containing NH4-sulfate tricyclic alcohol. Y ca. 50%. F. e. s. G. Stork et al.. Am. Soc. 87, 1148 (1965). 

Lam [77] has described highly enantioselective Cu(I)-catalyzed borylative aldol cyclizations of enone diones 237 via a chair-like transition state 238, which resulted in densely functionalized decalin-, hydrindane-, and diquinane-based products 239 containing four contiguous stereocenters, two of which are quaternary (Scheme 11.51). 

A soln. of benzenediazonium salt prepared from aniline, NaNOa, and 4%-HCl added portionwise with cooling at 0° to a stirred soln. of 3-ethoxycarbonylamino-l phenyl-5-pyrazolone in pyridine, and the product isolated after 12 hrs. -> 3-ethoxycarbonylamino-4-phenylhydrazono-l-phenyl-5-pyrazolone (Y 97%) refluxed in cw-decalin until crystals separate after 5-10 min. ->tetrahydro-2,6-di-phenylpyrazolo[3,4-e][l,2,4]triazine-3,7-dione (Y 94%). F. e. s. J. Slouka and P. Pec, M. 103, 1444 (1972). 

Ring contraction of the tetrahydro-l,3-diazepine-2,4,5-trione (197) in boiling decalin took place with elimination of phenyl isocyanate this method represents the conversion of a 2,3-dihydrofuran-2,3-dione (196) into a 2,3-dihydropyrrole-2,3-dione (198) thermolysis in the absence of solvent led to the quinoline (199). The zwitterionic 2,4-dioxopyrrolidine (200) was obtained in moderate yield by the condensation of o-(a-hydroxycinnamoyl)benzoic acid with tripiperidinomethane in ether-DMF at room temperature. ... 

The conformational situation in 9-methyl c/s-decalin-l,3-dione (342) and other 9-methyl ds-decalins has been investigated. In CDClj at 25 °C at higher concentrations (saturated solution is 0.42 mol 1 ), (342) exists as the keto-form to the extent of 80% and the enol form to the extent of 20% at 50 °C the corresponding figures are 90% and 10%. In dilute solution the proportion of keto form rises to 95 %. This behaviour parallels that of earlier cited results with cyclohexane-1,3-dione. It is considered that the keto-form consists of approximately equivalent proportions of (342a) and (342b). For (343) the axial P-proton at 5 3.28 p.p.m. with = 1 Hz was unaltered down to — 59 °C this, and an examination of models, supports the sole existence of the conformation shown in (343) under the conditions examined. In (344) the la-proton of... 

Figure 31 shows the reduction of 9-methyl-tran5-decalin-l,8-dione (66) with baker s yeast [79]. The major product 67 might be useful in isoprenoid synthesis. Reduction of... 

Figure 31 Reduction of 9-methyl-tranj-decalin-l,8-dione and bicyclo[3.3.1]nonane-2,8-diones with baker s yeast.

---