Deconjugative aldol-cyclization sequence for the construction of substituted 2-methoxytetrahydrofurans

Galatsis, Paul; Manwell, Jeffrey J.

doi:10.1016/0040-4039(95)01798-m

Cited by 12 publications

(8 citation statements)

References 14 publications

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“…No tetrahydrofuran formation was observed. This stands in sharp contrast to our previous results with the methyl ester, in which a mixture of oxetane and tetrahydrofuran was obtained 10a. For compounds 9 , 10 , 13 , and 14 , the formation of the oxetane is easily discerned via the primary iodide moiety.…”

Section: Resultscontrasting

confidence: 99%

“…The carbon of the primary iodide is very diagnostic and appears between −24 ppm for methyl iodide to about +10 ppm for alkyl iodides due to the heavy atom effect . We have observed this same chemical shift attribute in several of our other compounds. ,, The corresponding tetrahydrofuran would contain a secondary iodide, which would show a carbon shift significantly further downfield (ca. 20−40 ppm).…”

Section: Resultssupporting

confidence: 62%

“…The relative stereochemistry was determined by NOE measurements, while the absolute stereochemistry is assumed to be that which one would expect to be induced by the chiral auxiliary (the latter was shown to be true in an other system by X-ray analysis, vide infra ). The inability to isolate products from the phenyl derivative in the analogous methyl ester series was also observed in our earlier work . Since phenyl products can be obtained in other systems (see Table and our previous work 10 ), this would tend to indicate that the phenyl ring does not perturb the cyclization chemistry.…”

Section: Resultssupporting

confidence: 61%

“…The aldol reaction gave exclusively the α-alkylated deconjugated product with excellent enantiocontrol. The control observed in our earlier work with the methyl esters eroded in the cyclizations of 12 10b…”

Section: Resultsmentioning

confidence: 90%

“…These methods , include electrophile-induced (proton, halogen, metal, and chalogenide) reactions, oxidative cyclizations, ester enolate Claisen reactions, radical reactions, epoxide ring opening reactions, Michael additions, cycloadditions, and the use of carbohydrate precursors. In recent years, a renaissance in the electrophile-mediated cyclization of unsaturated alcohols has occurred. , However, this resurgence has focused on the 5- endo - trig mode of ring closure rather than the 5- exo - trig mode that is predicted by Baldwin's rules. We and others 9,10 have shown the feasibility of this method for the assembly of these systems.…”

Section: Introductionmentioning

confidence: 99%

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Enantioselective Construction of Cyclic Ethers by An Aldol-Cyclization Sequence

1997

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We have modified the substrate used in deconjugative aldol-cyclizations by incorporating the Evans chiral auxiliary. The deconjugative aldol step, using boron enolates, gave the expected products with complete syn-aldol stereochemistry. These compounds could then undergo an iodine-mediated cyclization to form optically active products. Oxetanes and fused ring tetrahydrofurans were easily assembled with a variety of substitution patterns and with excellent enantiocontrol. The deconjugation of acyclic chiral enimides resulted in the loss of control of olefin geometry. However, these compounds did appear to cyclize with excellent enantiocontrol.

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Section: Resultscontrasting

confidence: 99%

Section: Resultssupporting

confidence: 62%

Section: Resultssupporting

confidence: 61%

Section: Resultsmentioning

confidence: 90%

Section: Introductionmentioning

confidence: 99%

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Enantioselective Construction of Cyclic Ethers by An Aldol-Cyclization Sequence

1997

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Synthesis of Substituted Tetrahydrofuran by Electrophile-Induced Cyclization of 4-Pentene-1,2,3-triols − An Example of 5-exo versus 5-endo Cyclization Governed by the Electrophile

Bravo

Castillón

2001

Eur. J. Org. Chem.

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Differently protected 4-pentene-1,2,3-triols 5−8 were obtained from glyceraldehyde and submitted to iodine-based electrophile-induced cyclization to give tetrahydrofuran derivatives 10 and 18, with high chemo-, regio-, and stereoselectivity, through a 5-exo cyclization process. However, when an electrophilic selenium reagent was treated with similar alkene triols 5, 7, and 8, the product depended on the protecting group at the primary hydroxy moiety. Thus, while compounds 5a and 5b, unprotected at the primary hydroxy group, give compounds 26 and 27, and 32 and 33, respect-

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