Methylmagnesium carbonate preparation

Methylmagnesium carbonate was prepared by saturating an 8% solution of magnesium methoxide in methanol with carbon dioxide at room temperature (25°C) over 2 hr. The resultant solution was clear and colorless. Portions were diluted 10 1 with various solvents and observed for 24 hr for evidence of precipitation. The methanol solution was evaporated to dryness under vacuum on a steam bath, and a friable, glossy white solid was recovered solubility in a number of solvents was determined at the ratio of 1 g of solid in 50 mL solvent. 

The solubility of carbon dioxide in the solvent also affects the rate of reaction in the preparation of methylmagnesium carbonate as shown in Table I. In pure methanol the pH became constant after carbonation for 40 min at room temperature, indicating complete reaction, whereas in the methanol-Freon solvent, the reaction takes about 2 hr. 

A solution of methylmagnesium bromide in 150 ml of diethyl ether, prepared from 0.5 mol of methyl bromide (see Chapter II, Exp. 5) was subsequently added in 20 min with cooling at about 20°C. After the addition the mixture was warmed for 2 h under reflux (the thermometer and gas outlet were replaced with a reflux condenser), a black slurry being formed on the bottom of the flask. The mixture was cooled in a bath of dry-ice and acetone and a solution of 30 g of ammonium chlori.de in 200 ml of water was added with vigorous stirring. The organic layer and four ethereal extracts were combined, dried over potassium carbonate and subsequently concentrated in a water-pump vacuum. Careful distillation of the residue through a 40-cm... 

The monolithium salt of 4-hydroxy-4-(phenylethynyl)-2.5-cyclohexadienone (12), prepared in situ by the addition of lithium acetylide to /7-benzoquinone, was treated with methylmagnesium chloride in l HF-TMEDA or in THF —DMPU. The syn-, 4-addition adduct 13, derived from intramolecular delivery of the carbon nucleophile by the hydroxy oxygen, as well as the <7s-1,4-diol 14, obtained via intermolecular 1,2-addition, were obtained in varying amounts depending on the conditions. The selectivity on 1,4- to 1,2-addition increased by the addition of cation chelating agents such as DMPU, TMEDA, and 15-crown-5. Although the 1,4 to 1,2... 

Preparation of dithioacetic acid by addition of methylmagnesium iodide to carbon disulfide... 

Alkylations of 7i-allylpalladium complexes with organometallic compounds are restricted to the introduction of those alkyl moieties that do not offer the option of / -H elimination1. Efficient methylation of the stoichiometrically prepared complex 147,29 has been achieved with dimethylcadmium and methylmagnesium iodide, while methyllithium leads to preponderant reduction29. Complete retention, as well as exclusive alkylation at the more highly substituted carbon (see Table 25) is observed. 

What is the product of the reaction of methylmagnesium bromide with either of the enantiomerically pure epoxides that can be prepared from ( )-3-methyl-2-pentene by the preceding method Assign R or S configurations to the asymmetric carbons of each product. 

Dideoxy-DL-hexoses were prepared from 137 in the following way the carbon atom chain of the substrate was extended to a seven-carbon atom chain by a low temperature Grignard reaction with methylmagnesium bromide. The product obtained, 145, was separately cis-hydroxylated (to stereoisomeric tetraols 14<) or epoxidized (to epoxides 147). Products 146 and 147 were hydrolyzed and subsequently subjected to Ruff degradation. Pairs of stereoisomeric 2,6-dideoxy-DL-hexoses could be separated by column chromatography. Essentially the same approach served for a synthesis of 2-deoxy-DL-eo f/ ra-pentose. In this case compound 138 (X = OH) was used as a substrate for epoxidation. 

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