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Origin of ?-Facial Stereoselectivity in Thiophene 1-Oxide Cycloadditions.

ABSTRACT: We report a DFT computational study (M06-2X) of ?-facial selectivity in the Diels-Alder reactions of thiophene 1-oxide. The preference for the syn cycloaddition arises because the ground state geometry of thiophene 1-oxide is predistorted into an envelope conformation that resembles the syn transition state geometry. The syn distortion occurs to minimize the effect of hyperconjugative antiaromaticity in the thiophene 1-oxide, arising from overlap of the ?*SO with the ?-system. The syn selectivity follows through to the product structure that is stabilized by a ?-?*SO interaction, related to the 7-norbornenyl ion stability.

SUBMITTER: Levandowski BJ

PROVIDER: S-EPMC6314815 | biostudies-literature | 2018 Mar

REPOSITORIES: biostudies-literature

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Origin of π-Facial Stereoselectivity in Thiophene 1-Oxide Cycloadditions.

Levandowski Brian J BJ Herath Dinushka D Gallup Nathan M NM Houk K N KN

The Journal of organic chemistry 20180215 5

We report a DFT computational study (M06-2X) of π-facial selectivity in the Diels-Alder reactions of thiophene 1-oxide. The preference for the syn cycloaddition arises because the ground state geometry of thiophene 1-oxide is predistorted into an envelope conformation that resembles the syn transition state geometry. The syn distortion occurs to minimize the effect of hyperconjugative antiaromaticity in the thiophene 1-oxide, arising from overlap of the σ*<sub>SO</sub> with the π-system. The syn ...[more]

PMID: 29360357

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