Grignard reagents reaction with iodine

Lithiation of dibenzofuran with butyllithium and mercuration both occur at the 4-position. Thallation occurs at the 2-position, however (57IZV1391). The mercury and thallium derivatives serve as a source of the iodo compounds by reaction with iodine. Bromodibenzofurans undergo bromine/lithium exchange with butyllithium and the derived lithio compounds may be converted into phenols by reaction with molecular oxygen in the presence of a Grignard reagent, into amines by reaction with O-methylhydroxylamine, into sulfinic acids by reaction with sulfur dioxide, into carboxylic acids by reaction with carbon dioxide and into methyl derivatives by reaction with methyl sulfate (Scheme 100). This last reaction... 

A convenient synthesis of aryl glycines from Grignard reagents, prepared via iodine-magnesium exchange, was performed by the reaction with N-Boc-iminomalonate (from diethyl mesoxalate and BocN=PPh3). The reaction... 

The reaction with iodine has been used to provide evidence for the formation of Grignard reagents [A, 9]. 

In the case of Eu and Yb the reactions proceed at temperatures ranging from -40 to -20 C. Samarium is less active and after an activation by treatment with iodine interacts with RI at 30 C to give blue-green solutions of RSml. The solutions of Eu and Yb derivatives are brown. The products were not isolated from the reaction mixture as individual compounds, however the formation of them is reliably confirmed by the data of acidimetry and iodometry, reactions with iodine, as well as by reactions characteristic for Grignard reagents with Michler s ketone, water, benzophenone, Me3SiCl. The measurement of magnetic susceptibility has shown that in the Eu and Yb complexes from 85 to 100% of the metal is in bivalent state. In the Sm complexes up to 50% of the metal is present as Sm(III). 

Method 2. Equip a 1 htre thre necked flask with a double surface reflux condenser, a mechanical stirrer and a separatory funnel, and place 12 -2 g. of dry magnesium turnings, a crystal of iodine, 50 ml. of sodium-dried ether and 7-5 g. (5 ml.) of a-bromonaphthalene (Section IV,20) in the flask. If the reaction does not start immediately, reflux gently on a water bath until it does remove the water bath. Stir the mixture, and add a solution of 96 g. (65 ml.) of a-bromonaphthalene in 250 ml. of anhydrous ether from the separatory funnel at such a rate that the reaction is vmder control (1 -5-2 hours). Place a water bath under the flask and continue the stirring and refluxing for a further 30 minutes. The Grignard reagent collects as a heavy oil in the bottom of the flask ... 

Grignard reagents are normally prepared by the slow addition of the organic halide to a stirred suspension of magne.sium turnings in the appropriate solvent and with rigorous exclusion of air and moisture. The reaction, which usually begins slowly after an induction period, can be initiated by addition of a small crystal of iodine this penetrates the protective layer of... 

Specifically, it has recently been found 149) that diarylthallium tri-fluoroacetates may be converted into aromatic iodides by refluxing a solution in benzene with an excess of molecular iodine. Yields are excellent (74-94%) and the overall conversion represents, in effect, a procedure for the conversion of aromatic chlorides or bromides into aromatic iodides via intermediate Grignard reagents. The overall stoichiometry for this conversion is represented in Eq. (10), and it would appear that the initial reaction is probably formation of 1 mole of aromatic iodide and 1 mole of arylthallium trifluoroacetate iodide [Eq. (8)] which subsequently spontaneously decomposes to give a second mole of aromatic iodide and thallium(I) trifluoroacetate [Eq. (9)]. Support for this interpretation comes from the... 

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