Aliphatic Radical Relay Heck Reaction at Unactivated C(sp3)–H Sites of Alcohols

<div>The Mizoroki−Heck reaction is one of the most efficient methods for alkenylation of</div><div>aryl, vinyl, and alkyl halides. Due to its innate nature, this protocol requires the employment of compounds possessing a halogen atom at the site of functionalization. However, the accessibility of organic molecules possessing a halogen atom at a particular site in aliphatic systems is extremely limited. Thus, a protocol that would allow a Heck reaction to occur at a specific non-functionalized C(sp3)−H site would be highly desirable.</div><div>Here, we report a radical relay Heck reaction which allows for a selective remote</div>alkenylation of aliphatic alcohols at unactivated β-, γ- and δ-C(sp3 20 )–H sites. The use of easily installable/removable Si-based auxiliary enables selective I-atom/radical translocation events at remote C−H sites followed by the Heck reaction. Notably, the reaction proceeds smoothly under mild visible light-mediated conditions at room temperature, producing highly modifiable and valuable alkenol products from readily available alcohols feedstocks. <br>

Aliphatic Radical Relay Heck Reaction at Unactivated C(sp3)–H Sites of Alcohols

<div>The Mizoroki−Heck reaction is one of the most efficient methods for alkenylation of</div><div>aryl, vinyl, and alkyl halides. Due to its innate nature, this protocol requires the employment of compounds possessing a halogen atom at the site of functionalization. However, the accessibility of organic molecules possessing a halogen atom at a particular site in aliphatic systems is extremely limited. Thus, a protocol that would allow a Heck reaction to occur at a specific non-functionalized C(sp3)−H site would be highly desirable.</div><div>Here, we report a radical relay Heck reaction which allows for a selective remote</div>alkenylation of aliphatic alcohols at unactivated β-, γ- and δ-C(sp3 20 )–H sites. The use of easily installable/removable Si-based auxiliary enables selective I-atom/radical translocation events at remote C−H sites followed by the Heck reaction. Notably, the reaction proceeds smoothly under mild visible light-mediated conditions at room temperature, producing highly modifiable and valuable alkenol products from readily available alcohols feedstocks. <br>

1-ALKYL-3-METHYL-4-HYDROXYIMINO-2-PYRAZOLINE-5-ONES AS EXTRACTION REAGENTS

With nitrosation of the corresponding 1-R-3-methylpyrazole-5-one (R = C4H9, C5H11, C6H13, C7H15, C8H17, C6H5) in acidic aqueous methanolic medium at 0-5 °C a series of 1-alkyl-3-methyl-4-hydroxyimino-2-pyrazolin-5-ones with a yield of 72-85% were synthesized. The compounds are soluble in CHCl3, C2H4Cl2, C6H5CH3, i-C4H9OH, CCl4, C2H5OH, slightly soluble in C6H14, H2O. They can be recrystallized from a mixture of C6H14: C6H5CH3 = 5: 1 or isooctane. The structure of the compounds was confirmed by the data of ECR, IR, Raman spectroscopy and TLC data. The interphase distribution of oxyiminopyrazolones between chloroform and aqueous solutions was studied as a function of pH. In alkaline media, the reagents completely transferred into the aqueous phase. In acidic solutions, up to 1 mol/l HCl, the compounds are in the organic phase. The maximum values of the partition coefficient are observed for the reagents with the maximum length of the aliphatic radical. The effect of the length of aliphatic radical at the first position of the pyrazoline ring on their extraction properties were studied by example of extraction of nickel and copper (II) ions. The length of the radical does not affect the composition of the recoverable complexes of nickel and copper (II). In all cases the ratio is close to 1:2. Extraction proceeds through a cation-exchange mechanism. Replacement of the phenyl radical in the first position of the pyrazoline ring by an aliphatic resulted to the increase in partition constants of the reagents between chloroform and aqueous solutions. The range of pH values of the maximum extraction of elements was widened. The capacity of the extractant for metals also increased. At the same time, the pH50 extraction values remained practically unchanged. In the case of 0.05 mol/l solution of 1-phenyl-3-methyl-4-oxyimino-2-pyrazolin-5-one in chloroform, when the extract was saturated with the metal ion, precipitation of the complex was observed.For citation:Lesnov A.E., Pavlov P.T., Pustovik L.V., Sarana I.A. 1-Alkyl-3-methyl-4-hydroxyimino-2-pyrazoline-5-ones as extraction reagents. Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol. 2017. V. 60. N 5. P. 30-36.