1.4- cyclohexanedione monoethylene

Cyclohexanedione monoethylene acetal (l,4-dioxa-spiro[4.5]decan-8-one) [4746-97-8] M 156.2, m 70-73", 73.5-74.5". Recrystd from pet ether and sublimes slowly on attempted distillation. Also purified by dissolving in Et20 and adding pet ether (b 60-80°) until turbid and cool. [Gardner et al. J Am Chem Soc 22 1206 I957 Britten and Lockwood J Chem Soc Perkin Trans I 1824 1974.]... 

Cyclohexanedione monoethylene acetal (l,4-dioxa-spiro[4,5]decan-8-one) [4746-97-8]... 

One of the few examples of a synthetically useful 6-exo-trig cyclization from 3-aza-6-heptenyl radicals is found in the total synthesis of ( )-melinonine-E (159, Scheme 31) by Bonjoch et al. [66]. The cyclization precursor, a,P-unsaturated nitrile 157 was prepared from 1,4-cyclohexanedione monoethylene acetal (156) and tryptamine in 5 steps with 41% overall yield. Initially, when 157 was treated with 1.1 equiv. of n-BujSnH and 0.1 equiv. of AIBN in toluene for 16 h, the expected cyclization to the 2-azabicyclo[3.3.1]nonane ring took place to give 158 only as a minor product, along with its C(14) chloro- and dichloro-substituted derivatives as major products. An additional treatment of the crude mixture with 2.2 equiv. of BujSnH brought about the reduction of the C-Cl bonds to provide nitrile 158 in 38% yield over... 

Camps et al. developed a route to ( )-HA from a keto capamate 7, which was obtained in 22% overall yield from 1,4-cyclohexanedione monoethylene ketal (3) (Scheme 4-5). ° This new approach to racemic HA features the elaboration of the pyridone moiety of HA in a late stage. In this way, we can access the different heterocyclic analogs instead of the pyridone moiety in HA. However, the total yield of HA was not markedly improved, compared with that of other approaches, and the purification of the isomers proved to be a tedious and difficult task. 

The structure of huperzine A was confirmed by total synthesis. There are several reports on total synthesis [27]. The following described was recently accomplished by Kozikowski s group [28,29]. The monoprotected diketone, 1,4-cyclohexanedione monoethylene ketal 5-4 was used as starting material. The pyrrolidine enamine of 5-5 was heated with acrylamide followed by hydrolysis to provide an 85 15 mixture of the lactam 5-6 and 5-7. After protection of the lactam nitrogen by benzylation, dehydrogenation of the latter mixtures afforded pyridone 5-8, then hydrogenolysis of its N-benzyl group, followed by O-methylation with methyl iodide and silver carbonate which yielded methoxypyridine 5-... 

In this original and imaginitive approach, a rapid assembly of the phenanthrene core of morphine, containing a novel non-aromatic A ring, was achieved in an intermolecular Diels-Alder reaction between quinone 173 (prepared from 3-methoxy-2-hydroxy benzaldehyde in 7 steps and an overall yield of 35%) and diene 174 (from 1,4-cyclohexanedione monoethylene ketal in 2 steps with an overall yield of 30%), Scheme 20. In one of several unsuccesful attempts to aromatize ring A, an unexpected tandem... 

Condensation of hydroxylamine rac-10 with 1,4-cyclohexanedione monoethylene acetal provided nitrone rac-9, which was treated with ethyl acrylate to give 74% of a 8-9 1 mixture of isoxazolidine rac-8 and its diastereomer. Reduction of this mixture with hydrogen afforded 8-9 1 of a mixture of lactam rac-1 and its diastereomer (Scheme 7). After crystallization, X-ray analysis of the major product confirmed that its stereochemistry is the one required for carrying out the synthesis of FR901483. The excellent stereoselectivity observed in the 1,3-dipolar cycloaddition of nitrone rac-9 was attributed to the substitution pattern in the stereogenic center adjacent to the nitrogen atom. These substituents stabilize one chair conformer relative to the other and thus allow a good... 

Chiral nonracemic enamines formed in situ by reaction of aldehydes and ketones with proline-based organocatalysts also undergo stereoselective a-oxygenation. MacMillan and coworkers have achieved enantioselective a-oxidation of a range of aliphatic aldehydes such as (5.87) with 97-99% ee using proline in combination with nitrosobenzene (5.85). This method can be applied to the aminoxylation of six-membered cyclic ketones such as 1,4-cyclohexanedione monoethylene ketal (5.88). 59... 

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