Thermal Isomerisation of 2-Alkyl-3-bromotetrahydrofurans and 2-Alkyl-3-bromotetrahydropyrans

Polivin, Yurii N.; Караханов, Р. А.; Уграк, Б. И.; Заикин, В. Г.; Makarshin, S. V.; Келарев, В. И.

doi:10.1070/mc1994v004n01abeh000334

Cited by 3 publications

(1 citation statement)

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“…Then, the bromoderivative 1 was converted into (2 S ,3 R )- 3 modifying the procedure adopted for the SN2 of 11 . Indeed, accidentally during the bulb-to-bulb distillation of (2 S ,3 S )- 1 at high temperature (110 °C, 15 mmHg), we found that the product isomerized to the trans diastereoisomer ( cis / trans 1:1 by 1 H NMR; see the SI), and it decomposed as well. Thus, in order to avoid these side reactions during the nucleophilic substitution with AcSK, it is crucial to carry out the reaction at a temperature below 100 °C in DMSO and in the presence of dibenzo-18-crown-6.…”

Section: Resultsmentioning

confidence: 99%

Exploitation of a Multienzymatic Stereoselective Cascade Process in the Synthesis of 2-Methyl-3-Substituted Tetrahydrofuran Precursors

et al. 2017

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Enantiopure 2-methyl-3-substituted tetrahydrofurans are key precursors of several biologically active products (drugs, flavors, and agrochemicals). Thus, a stereocontrolled and efficient methodology for the obtainment of these synthons is highly desirable. We exploited a two-step multienzymatic stereoselective cascade reduction of α-bromo-α,β-unsaturated ketones to give the corresponding bromohydrins in good yields, with high ee and de values. The cascade process is catalyzed by an ene-reductase and an alcohol dehydrogenase. Further manipulations of these bromohydrins, by two diastereodivergent routes, allowed the preparation of the tetrahydrofuran synthons. One route is based on a lipase catalyzed cleavage of the protecting group. The second route is characterized by a camphor sulfonic acid mediated isomerization of a β-hydroxyepoxide to give the tetrahydrofuran-2-ol. Finally, the synthesis of the most odorous and pleasant stereoisomer of the roasted meat aroma, i.e., (2S,3R)-2-methyl-3-thioacetate tetrahydrofuran, is reported as well.

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Section: Resultsmentioning

confidence: 99%