Dataset Information

Halogenation Reactions of Alkyl Alcohols Employing Methyl Grignard Reagents.

ABSTRACT: Grignard reagents are commonly used as carbanion equivalents. Herein, we report an example of Grignard reagents acting as halide nucleophiles to form alkyl iodides and bromides. We establish that Grignard reagents can convert alkyl mesylates into alkyl halides, as well as be employed in a one-pot halogenation reaction starting from alcohols, which proceed through mesylate intermediates. The halogenation reaction is confirmed to occur by an S_N2 pathway with inversion of configuration and is demonstrated to be efficient on multi-gram scale.

SUBMITTER: Hirbawi N

PROVIDER: S-EPMC9486953 | biostudies-literature | 2022 Sep

REPOSITORIES: biostudies-literature

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Halogenation Reactions of Alkyl Alcohols Employing Methyl Grignard Reagents.

Hirbawi Nadia N Lin Patricia C PC Jarvo Elizabeth R ER

The Journal of organic chemistry 20220901 18

Grignard reagents are commonly used as carbanion equivalents. Herein, we report an example of Grignard reagents acting as halide nucleophiles to form alkyl iodides and bromides. We establish that Grignard reagents can convert alkyl mesylates into alkyl halides, as well as be employed in a one-pot halogenation reaction starting from alcohols, which proceed through mesylate intermediates. The halogenation reaction is confirmed to occur by an S<sub>N</sub>2 pathway with inversion of configuration a ...[more]

PMID: 36049783

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Project description:We describe the mechanism, substituent effects, and origins of the selectivity of the nickel-catalyzed four-component coupling reactions of alkyl fluorides, aryl Grignard reagents, and two molecules of 1,3-butadiene that affords a 1,6-octadiene carbon framework bearing alkyl and aryl groups at the 3- and 8-positions, respectively, and the competing cross-coupling reaction. Both the four-component coupling reaction and the cross-coupling reaction are triggered by the formation of anionic nickel complexes, which are generated by the oxidative dimerization of two molecules of 1,3-butadiene on Ni(0) and the subsequent complexation with the aryl Grignard reagents. The C-C bond formation of the alkyl fluorides with the γ-carbon of the anionic nickel complexes leads to the four-component coupling product, whereas the cross-coupling product is yielded via nucleophilic attack of the Ni center toward the alkyl fluorides. These steps are found to be the rate-determining and selectivity-determining steps of the whole catalytic cycle, in which the C-F bond of the alkyl fluorides is activated by the Mg cation rather than a Li or Zn cation. ortho-Substituents of the aryl Grignard reagents suppressed the cross-coupling reaction leading to the selective formation of the four-component products. Such steric effects of the ortho-substituents were clearly demonstrated by crystal structure characterizations of ate complexes and DFT calculations. The electronic effects of the para-substituent of the aryl Grignard reagents on both the selectivity and reaction rates are thoroughly discussed. The present mechanistic study offers new insight into anionic complexes, which are proposed as the key intermediates in catalytic transformations even though detailed mechanisms are not established in many cases, and demonstrates their synthetic utility as promising intermediates for C-C bond forming reactions, providing useful information for developing efficient and straightforward multicomponent reactions.

Dataset Information

Halogenation Reactions of Alkyl Alcohols Employing Methyl Grignard Reagents.

Publications

Halogenation Reactions of Alkyl Alcohols Employing Methyl Grignard Reagents.

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