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Aryl Carbamates: Mechanisms of Orthosodiations and Snieckus-Fries Rearrangements.

ABSTRACT: Aryl carbamates are orthometalated by sodium diisopropylamide (NaDA) in tetrahydrofuran. The resulting arylsodiums undergo Snieckus-Fries rearrangement to give orthoacylated phenols in good yield. The intermediate arylsodiums and resulting orthoacylated phenolates are suggested to be monomeric. The rate-limiting step in the two-step sequence depends on the steric demands of the carbamoyl moiety and the substituents in the meta position of the arene. Rate studies reveal a dominant disolvated-monomer-based orthometalation followed by a di- or trisolvated arylsodium monomer-based rearrangement. Kinetic evidence of a NaDA-catalyzed Snieckus-Fries rearrangement suggests the intermediacy of mixed trimers. Competitive halide eliminations to form benzyne are also discussed.

SUBMITTER: Ma Y

PROVIDER: S-EPMC7050188 | biostudies-literature | 2019 Jul

REPOSITORIES: biostudies-literature

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Aryl Carbamates: Mechanisms of Orthosodiations and Snieckus-Fries Rearrangements.

Ma Yun Y Woltornist Ryan A RA Algera Russell F RF Collum David B DB

The Journal of organic chemistry 20190701 14

Aryl carbamates are orthometalated by sodium diisopropylamide (NaDA) in tetrahydrofuran. The resulting arylsodiums undergo Snieckus-Fries rearrangement to give orthoacylated phenols in good yield. The intermediate arylsodiums and resulting orthoacylated phenolates are suggested to be monomeric. The rate-limiting step in the two-step sequence depends on the steric demands of the carbamoyl moiety and the substituents in the meta position of the arene. Rate studies reveal a dominant disolvated-mono ...[more]

PMID: 31257864

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