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Practical One-Pot Multistep Synthesis of 2H-1,3-Benzoxazines Using Copper, Hydrogen Peroxide and Triethylamine.

ABSTRACT: In this article, we describe simple one-pot syntheses of 2H-1,3-benzoxazines from ketones utilizing an imino-pyridine directing group (R¹R²-C=N-CH₂-Pyr), which promotes a Cu-directed sp² hydroxylation using H₂O₂ as oxidant and followed by an oxidative intramolecular C-O bond formation upon addition of NEt₃. This synthetic protocol is utilized in the gram scale synthesis of the 2H-1,3-benzoxazine derived from benzophenone. Mechanistic studies reveal that the cyclization occurs via deprotonation of the benzylic position of the directing group to produce a 2-azallyl anion intermediate, which is oxidized to the corresponding 2-azaallyl radical before the C-O bond formation event. Understanding of the cyclization mechanism also allowed us to develop reaction conditions that utilize catalytic amounts of Cu.

SUBMITTER: Trammell R

PROVIDER: S-EPMC8442982 | biostudies-literature | 2021 Aug

REPOSITORIES: biostudies-literature

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Practical One-Pot Multistep Synthesis of 2H-1,3-Benzoxazines Using Copper, Hydrogen Peroxide and Triethylamine.

Trammell Rachel R Cordova Alexandra A Zhang Shuming S Goswami Sunipa S Murata Richel R Siegler Maxime A MA Garcia-Bosch Isaac I

European journal of organic chemistry 20210817 32

In this article, we describe simple one-pot syntheses of 2H-1,3-benzoxazines from ketones utilizing an imino-pyridine directing group (R1R2-C=N-CH2-Pyr), which promotes a Cu-directed sp2 hydroxylation using H2O2 as oxidant and followed by an oxidative intramolecular C-O bond formation upon addition of NEt3. This synthetic protocol is utilized in the gram scale synthesis of the 2H-1,3-benzoxazine derived from benzophenon ...[more]

PMID: 34539234

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