Grignard reagent formation via C-F bond activation: a centenary perspective

Examples of Grignard reagents obtained by C-F bond activation with magnesium kept appearing in the literature over the last century. Due to the high bond dissociation energy of the C-F...

Radiochemical Studies of Hydrogen Exchange in Organic Compounds

<p>A property of a new or unknown organic compound which must be determined once the empirical formula and molecular weight are known, is the number of active or replaceable hydrogen atoms which the compound contains. These include hydrogen atoms present in amine, hydroxyl, carboxyl and other groups, where the hydrogen is not bound to a carbon atom but to an oxygen, nitrogen or sulphur atom or is in a position where it can ionize. The most general method by which this may be done quantitatively, is the one originally due to Zerewitinoff Zerewitinoff - Berichte 40 2023 (1907) 41 2233 (1908) 42 4802 (1909) 43 3590 (1910) 47 1659 (1914) 47 2417 (1914) and since developed on a micro scale by Roth A. Soltys Mikrochemie 20 107 (1936), Flaschentrager A. Roth Mikrochemie 11 140 (1932), whose method incorporates work by Tschugaeff - Flaschentrager z. Physiol Chem. 146 219 (1923) and the other two authors, and Soltys L. Tschugaeff Berichte 35 3912 (1902), and incorporates many of the latest improvements. This involves the quantatatively evolution of methane from reaction of the Grignard reagent MeMgI on groups such as -SH, -OH, -NH2, -COOH etc., i.e. those groups containing active or replaceable hydrogen atoms. Analysis by this method requires extreme care in technique and exact attention to experimental details. High results are obtained if the solvent or any part of the apparatus contains moisture and the whole determination must be carried out in an atmosphere of nitrogen to avoid reaction of the Grignard reagent with any oxygen present. Low results are obtained if the test solution does not dissolve completely in the chosen solvent and it is essential to carry out a blank prior to each analysis. The proceedure is labourious and painstaking and gives an accuracy of not greater than 5% using 3-5 mgm of organic compound. It also has the disadvantage that the Grignard Reagent will also react with other groups, such as carbonyl, aldehyde, nitrile etc., which may be present. This method cannot be applied to highly water soluble compounds which do not dissolve in ethers or other organic solvents and as the molecular size or complexity of the sample increases, the accuracy of the gasometric reactions becomes less, due to side reactions and incomplete reaction.</p>

Radiochemical Studies of Hydrogen Exchange in Organic Compounds

<p>A property of a new or unknown organic compound which must be determined once the empirical formula and molecular weight are known, is the number of active or replaceable hydrogen atoms which the compound contains. These include hydrogen atoms present in amine, hydroxyl, carboxyl and other groups, where the hydrogen is not bound to a carbon atom but to an oxygen, nitrogen or sulphur atom or is in a position where it can ionize. The most general method by which this may be done quantitatively, is the one originally due to Zerewitinoff Zerewitinoff - Berichte 40 2023 (1907) 41 2233 (1908) 42 4802 (1909) 43 3590 (1910) 47 1659 (1914) 47 2417 (1914) and since developed on a micro scale by Roth A. Soltys Mikrochemie 20 107 (1936), Flaschentrager A. Roth Mikrochemie 11 140 (1932), whose method incorporates work by Tschugaeff - Flaschentrager z. Physiol Chem. 146 219 (1923) and the other two authors, and Soltys L. Tschugaeff Berichte 35 3912 (1902), and incorporates many of the latest improvements. This involves the quantatatively evolution of methane from reaction of the Grignard reagent MeMgI on groups such as -SH, -OH, -NH2, -COOH etc., i.e. those groups containing active or replaceable hydrogen atoms. Analysis by this method requires extreme care in technique and exact attention to experimental details. High results are obtained if the solvent or any part of the apparatus contains moisture and the whole determination must be carried out in an atmosphere of nitrogen to avoid reaction of the Grignard reagent with any oxygen present. Low results are obtained if the test solution does not dissolve completely in the chosen solvent and it is essential to carry out a blank prior to each analysis. The proceedure is labourious and painstaking and gives an accuracy of not greater than 5% using 3-5 mgm of organic compound. It also has the disadvantage that the Grignard Reagent will also react with other groups, such as carbonyl, aldehyde, nitrile etc., which may be present. This method cannot be applied to highly water soluble compounds which do not dissolve in ethers or other organic solvents and as the molecular size or complexity of the sample increases, the accuracy of the gasometric reactions becomes less, due to side reactions and incomplete reaction.</p>

Ruthenium Metal: Uplifting Regioselective C-H activation

: Construction of the C-C bond has always been a challenge for organic chemists, because of the reactivity of carbon atoms. The making of nucleophilic carbon started with the Grignard reagent, enolate, and the ylide, moreover, the aromatic carbon activation was the challenge before the era of organometallic chemistry. The recognition of organometallic chemistry was in the light when the Nobel Prize was given for the C-C bond in the year 2010, However, The pre functionalization of the C-H bond was an additional step with halogenated reagent, which was the limitation of this reaction. Later the C-H activation with organometals like Pd, Ru, Cu, Rh, and other transition metal came into existence, where the directing group and metal makes feasibility to form the nonreactive C-C bond. In spite of several organometals, Ru made a special place due to the reactivity, coast and, stability. Various C-H activation reaction protocols were reported with their high regioselectivity as well as high atom economy. The C-H activation protocol is now in the next level of development like SP3, SP2 ortho, meta, and para C-H activation. Here in our aim is to get the summarized information regarding the Ru and their ortho -regioselective reactions with the help of the directing group. The reader will be benefited from the mechanistic part and the concept of C-H activation with some of the important examples, which have been summarized here in with the various Ru based regioselective reactions through weak and strong coordination of metal and substrate.

Diastereoselective Synthesis of Morpholine Derivatives from Grignard Reagents and N-Sulfinyl Imines

The stereoselective synthesis of C3-substituted morpholine derivatives has been achieved through a two-step process involving diastereoselective addition of a Grignard reagent to a sulfinyl imine, followed by cyclization.

Unveiling the Reaction Mechanism of the Das/Chechik/Marek Synthesis of Stereodefined Quaternary Carbon Centers

The reaction mechanism of the Cu+-catalyzed introduction of two all-carbon-substituted stereocenters in an ynamide system using a Grignard reagent, a zinc carbenoid, and an aldehyde, was investigated using density-functional theory. In contrast to the formation of an organocopper(I) compound and subsequent carbocupration reaction, previously postulated as the initial step, the reaction proved to instead proceed through an initial complexation of the substrate alkyne bond by the Cu+-catalyst, which primes this bond for reaction with the Grignard reagent. Subsequent addition of the zinc carbenoid then enables the nucleophilic attack on the incoming aldehyde, which is revealed as the rate-limiting step. Our computations have also identified the factors governing the regio- and setereoselectivity of this interesting reaction, and suggest possible paths for its further development

Applications of ytterbium(II) reagent as Grignard reagent and single electron transfer reagent in the synthesis of 3-substituted-2-oxindoles

The utilities of ytterbium(II) reagent, both as nucleophilic reagent and single electron transfer reagent in the reaction of isatin derivatives with ytterbium(II) reagent are reported for the first time in this paper. From a synthetic point of view, a general, efficient, and experimentally simple one-pot method for preparation of 3-substituted-2-oxindoles was developed.