Name | Methylboronic acid |
Synonyms | CH5BO2 METHYLBORONIC ACID Methylboranic acid Methylboronic acid METHANEBORONIC ACID METHYLBORON DIHYDROXIDE dihydroxy-methyl-borane METHYLBORONIC ACID FOR GC METHANDROSTENOLONE PHARMA-0463 Methylboron dihydroxide, GLC Grade |
CAS | 13061-96-6 |
EINECS | 629-203-8 |
InChI | InChI=1/CH5BO2/c1-2(3)4/h3-4H,1H3 |
InChIKey | KTMKRRPZPWUYKK-UHFFFAOYSA-N |
Molecular Formula | CH5BO2 |
Molar Mass | 59.86 |
Density | 0.965±0.06 g/cm3(Predicted) |
Melting Point | 91-94 °C (lit.) |
Boling Point | 141.7±23.0 °C(Predicted) |
Flash Point | 39.5°C |
Water Solubility | Soluble in water. |
Solubility | DMSO, Water |
Vapor Presure | 2.35mmHg at 25°C |
Appearance | White to light yellow crystal powder |
Color | White to off-white |
BRN | 1731087 |
pKa | 9.97±0.43(Predicted) |
Storage Condition | Inert atmosphere,Store in freezer, under -20°C |
Sensitive | Hygroscopic |
Refractive Index | 1.345 |
MDL | MFCD00002105 |
Physical and Chemical Properties | Sensitivity: hydrogen WGK Germany:3 |
Hazard Symbols | Xi - Irritant![]() |
Risk Codes | 36/37/38 - Irritating to eyes, respiratory system and skin. |
Safety Description | S26 - In case of contact with eyes, rinse immediately with plenty of water and seek medical advice. S36 - Wear suitable protective clothing. |
WGK Germany | 3 |
FLUKA BRAND F CODES | 3-10 |
HS Code | 29319090 |
Hazard Note | Irritant/Keep Cold |
Hazard Class | IRRITANT |
Overview | Catalytic asymmetric reduction is an important way to obtain chiral compounds, as the most classic reduction of carbonyl compounds Catalyst: MeCBS and borane are combined to prepare chiral alcohols. This method is still widely used due to its high enantioselectivity. As one of the most important reagents, the synthesis of methyl boric acid still lacks an effective method. At present, there are two main methods for synthesizing methylboric acid. One is that borane reacts with carbon monoxide to hydrolyze to obtain methylboric acid. In this method, borane is a flammable gas. Carbon monoxide is highly toxic. Once it leaks, it is very dangerous. The other is that the methyl Grignard reagent reacts with a special unstable chloroboric reagent to hydrolyze to obtain methyl boric acid, which will inevitably be generated by the by-product trimethyl boron, and the properties of trimethyl boron are very active, It is easy to spontaneously ignite with the air, which brings safety hazards to production. Secondly, methylboric acid is very water-soluble and is not easy to extract in aqueous solution, wasting a lot of solvent. |
Application | Methylboronic acid is the simplest organic boronic acid derivative. It is an important intermediate for the preparation of many boronic acid derivatives such as (S) or (R)-2-methyl-CBS-oxazoborane, which has many uses in organic synthesis. In addition, methyl boric acid and its derivatives also have significant advantages in chromatographic analysis, and are often used for the separation of cis-trans isomers. |
preparation | 1) synthesis of (trimethylsilyl) methylboronic acid: under the protection of nitrogen, magnesium metal (0.33 mol) and a few small grains of iodine are added to the reaction bottle equipped with a condenser tube and a constant pressure feeding funnel, under stirring, drop 30 ml of a mixed solution of trimethylsilyl bromide (0.3 mol) dissolved in 250 ml of 2-methyltetrahydrofuran. Heat to above 40°C, and slowly drop the remaining solution after the reaction is initiated. The temperature is raised to reflux reaction for 3 hours, and it is reduced to room temperature. In another reaction bottle, under the protection of nitrogen, add trimethyl borate (0.35 mol) and 80 ml of 2-methyltetrahydrofuran, after stirring evenly, cool to -20 ℃, slowly add the prepared Grignard reagent, add it for 2-3 hours, keep the temperature and continue the reaction for 2-2.5 hours, when confirming that the reaction does not change, heat up to 0 ℃, add 10% hydrochloric acid to adjust PH = 2. The water layer is extracted once with 2-methyltetrahydrofuran, and the organic layer is combined to be directly used in the next synthesis; 2) Synthesis of methyl boric acid trimer: add the organic layer obtained above to the reaction bottle with a reflux water separation device, tetra-n-butylammonium fluoride water and substance (0.4 moles), the system is quickly dissolved under room temperature stirring, after the reaction is completed, the system solvent is evaporated to dry under normal pressure, and the mixture is added with 120 ml of toluene, start to reflux and separate water. When the water exceeding the calculated amount is separated, and there is no more water to continue to separate, connect to the rectification device to distill the methyl boric acid trimer generated after the reaction. 3) Synthesis of methyl boric acid: After adding 4.5 grams of water to the trimer of methyl boric acid obtained after rectification, stirring at room temperature for 30 minutes, and solid precipitation. After adding n-heptane for beating, filtering to obtain 11.2g of white solid methyl boric acid with 62% yield, GC:98.2%, melting point 88-90 ℃, and nuclear magnetic structure. |