Background and overview[1]
1-Naphthylmethanol is a primary alcohol and an important organic compound. It is not only an important pharmaceutical intermediate, but also widely used in spices, foods, etc. In traditional methods, you can use high-temperature and high-pressure hydrogenation, add inorganic reducing agents such as sodium borohydride, or use formic acid and sodium formate to prepare primary alcohols. These methods have safety hazards, produce a large amount of waste, and cause certain pollution to the environment. In recent years, preparation using isopropanol as a hydrogen source, which is a cheap, safe, non-toxic hydrogen donor, has received widespread attention. However, a strong base or a weak base needs to be added during the reaction. Therefore, from the perspective of organic synthesis, a new type of organometallic catalyst is developed. By using cheap, safe, non-toxic isopropyl alcohol as the hydrogen source and solvent, there is no need to use alkali in the reaction, and it can be carried out in an environmentally friendly and mild state. Catalyzing this type of reaction is of great significance.
Preparation method[1]
Method 1: Add 1-naphthaldehyde (158mg, 1.0mmol), cat.[Ir] (1.1mg, 0.002mmol, 0.2mol%) and isopropanol (5mL) into a 25mL Kirschner tube in sequence. N2 protection, reaction at 82°C for 6 hours. Cool to room temperature, remove the solvent by rotary evaporation, and then obtain the pure target compound through column chromatography (developing solvent: petroleum ether/ethyl acetate), yield: 95%
1HNMR (500MHz, CDCl3) δ8.15 (d, J=8.4Hz, 1H), 7.89 (d, J=7.8Hz, 1H), 7.83 (d, J=8.2Hz, 1H), 7.57-7.50 (m, 3H), 7.45 (t, J=7.6Hz, 1H), 5.17 (s, 2H), 1.74 (brs, 1H); 13CNMR (125MHz, CDCl3) δ136.2, 133.7, 131.1, 128.6, 128.4, 126.2, 125.8, 125.3, 125.2, 123.6, 63.4.
Method 2: Under an inert gas N2 atmosphere, add 1-naphthoic acid (85.4 mg, 0.5 mmol) to the reaction bottle that has been dehydrated and deoxygenated, and use a pipette to add pinacolborane (289 μL, 2 mmol) , react at room temperature for 12 hours, remove the reaction from the glove box, use mesitylenetrimethoxybenzene (83.42mg, 0.5mmol) as the internal standard, dissolve it with CDCl3, stir for 10 minutes, take a sample, and configure NMR. The calculated 1H yield is 91%. NMR data of the product: 1HNMR (MHz, CDCl3): δ8.02 (d, 1H, ArCH), 7.80-7.82 (m, 2H, ArCH), 7.75 (d, 1H, ArCH), 7.38-7.48 ( m, 3H, ArCH), 5.37 (s, 2H, OCH2), 1.23 (s, 36H, CH3). Add 1g silica gel to the sampling residue, use 3mL methanol as the solvent, react at 50°C for 3h, and the borate ester Further hydrolyze into alcohol. After the reaction, extract with ethyl acetate three times, combine the organic layers, dry with anhydrous sodium sulfate, remove the solvent under reduced pressure, purify by silica gel (100-200 mesh) column chromatography, use ethyl acetate/ Hexane (1:5) mixture was used as the eluent to obtain pure 1-naphthalenemethanol, with an isolation yield of 91%. NMR data of the product: 1HNMR (MHz, CDCl3): δ8.02 (d, 1H, ArCH) , 7.80-7.82 (m, 2H, ArCH), 7.73 (d, 1H, ArCH), 7.38-7.48 (m, 3H, ArCH), 5.01 (s, 2H, CH2), 2.31 (brs, 1H, OH).
Main reference materials
[1] CN201710683922.0 A method of synthesizing primary alcohol
[2] CN201811585437.0 A method for preparing alcohol compounds from the non-catalytic reaction of aromatic carboxylic acids
