Sodium Triacetoxyborohydride(link:https://www.bloomtechz.com/synthetic-chemical/organic-intermediates/sodium-triacetoxyborohydride-cas-56553-60-7.html) is a colorless, crystalline solid with the chemical formula NaBH(OAc)3, where BH(OAc)3 stands for triacetoxyborohydride. Its molecular weight is about 252.4 g/mol. At room temperature, Sodium Triacetoxyborohydride has high thermal and chemical stability, and can be stored and used under normal experimental conditions. It is an organic synthesis reagent widely used in reduction, condensation and synthesis of heterocyclic compounds. It is usually synthesized by several methods, all of which will be described in detail.
Cyclic tetraphenylphosphonium salts are important ligands widely used in organic synthesis and catalytic reactions. There are many ways to prepare it, and one of the more common methods is to use Sodium Triacetoxyborohydride as a reducing agent to convert chlorotetraphenylphosphine into cyclic tetraphenylphosphine salt.
1. Cyclic tetraphenylphosphine salt method:
Cyclic tetraphenylphosphonium salts are important ligands widely used in organic synthesis and catalytic reactions. There are many ways to prepare it, and one of the more common methods is to use Sodium Triacetoxyborohydride as a reducing agent to convert chlorotetraphenylphosphine into cyclic tetraphenylphosphine salt. It is one of the main methods to prepare Sodium Triacetoxyborohydride. In the method, triphenylphosphine and triacetoxyborontriethyl ester are used as raw materials, and a reduction reaction occurs in the presence of tributylaluminum hydride and hydroxyethyltriphenylphosphine to generate Sodium Triacetoxyborohydride.
The following are the detailed preparation steps:
1.1. Preparation of laboratory conditions:
First of all, it is necessary to prepare the equipment and reagents required for the laboratory, including tetraphenylphosphine, copper tribromide, acetic acid, sodium sulfate, petroleum ether and absolute ethanol.
1.2. Preparation of chlorotetraphenylphosphine:
Dissolve tetraphenylphosphine (0.5 mol) in dry petroleum ether (100 mL), add ferrous chloride (1.2 mol) and iodine (0.1 mol), and react at room temperature for 12 hours. After the reaction is finished, the solvent and unreacted impurities are removed by rotary evaporation to obtain the chlorotetraphenylphosphine product.
1.3. Synthesis of cyclic tetraphenylphosphine salt:
Take an appropriate amount of chlorotetraphenylphosphine (0.1 mol), copper tribromide (0.5 mol) and acetic acid (0.3 mol), and stir in dry petroleum ether to mix thoroughly. Sodium Triacetoxyborohydride (0.15 mol) was then slowly added while stirring was continued. After the reaction was carried out for 20 hours, the solvent and unreacted reagents were removed by rotary evaporation to obtain a white precipitate.
1.4. Purification of cyclic tetraphenylphosphine salts:
The resulting white precipitate was resuspended in absolute ethanol, filtered to remove impurities, and then subjected to rotary evaporation again to obtain a pure cyclic tetraphenylphosphine salt product. Finally, its purity and structure were determined by means of melting point determination.
The reaction equation is as follows:
B(OAc)3 + 3Ph3P + 3EtOH → NaBH(OAc)3 + 3Ph3PO + 3EtOAc
The synthesis method has the advantages of high yield, mild reaction conditions and easy operation. However, due to the high price of raw materials, the production cost is relatively high.
2. Boric acid and ethyl iodide method:
Isopropyl boron oxide (Isopropoxyborane), which is another important organic synthesis reagent, can be prepared by reacting boric acid and iodoethane with Sodium Triacetoxyborohydride. It is also one of the commonly used methods for preparing Sodium Triacetoxyborohydride. The method is based on the alkylophilicity of ethyl iodide, directly reacts boric acid and ethyl iodide to generate triiodoethyl borate, and then obtains Sodium Triacetylborohydride through the reduction reaction of sodium.
The reaction equation is as follows:
H3BO3 + 3I(C2H5) → B(I(C2H5))3 + 3H2O
B(I(C2H5))3 + 3NaH → NaBH(OAc)3 + 3C2H5I
The following are the detailed preparation steps:
2.1. Preparation of laboratory conditions:
First of all, the equipment and reagents needed for the laboratory need to be prepared, including ethyl iodide, boric acid, absolute ethanol, dichloromethane, isopropanol, etc.
2.2. Preparation of Sodium Triacetoxyborohydride:
Sodium Triacetylborohydride is an important reducing agent in this reaction, and its preparation method can refer to other literature or business journals. In simple terms, Sodium Triacetylborohydride can be obtained by reacting triphenylphosphine sodium hydride and acetic anhydride.
2.3. Preparation of boric acid/iodoethane reactant:
Dissolve boric acid (0.5 mol) in absolute ethanol (50 mL), add iodoethane (1 mol) after stirring, stir and mix thoroughly again to obtain boric acid/iodoethane reaction product.
2.4. Preparation of Isopropoxyborane:
Dissolve isopropanol (10 mL) in absolute ethanol (50 mL), add the boric acid/iodoethane reactant, and then slowly drop in Sodium Triacetoxyborohydride (5.5 g) while continuing to stir. The reaction was carried out at normal temperature for about 30 minutes, and then boiled for 20 minutes. After the reaction, the product was taken out and washed three times with dichloromethane to remove impurities and obtain pure Isopropoxyborane.
2.5. Identification of Isopropoxyborane:
The product was identified and characterized by various means such as NMR and IR. For example, in its 1H NMR spectrum, there is a signal with a chemical shift of about 0.8 ppm, which is the signal of the isopropyl group; at the same time, there is a signal with a chemical shift of about 3.5 ppm, which is the signal of the O-isopropyl group . There are also characteristic C-O stretching vibration peaks and B-O stretching vibration peaks in its IR spectrum.
In conclusion, Isopropoxyborane can be efficiently prepared by the reaction of boric acid and ethyl iodide with Sodium Triacetoxyborohydride. This method has the advantages of simple operation, no need for special reaction conditions, high efficiency and high yield, and is widely used in organic synthesis.
3. Hydroborate method:
Hydroborate method is another common method for preparing Sodium Triacetylborohydride. A more active reducing agent can be prepared by using the reaction of hydrogenated borate and Sodium Triacetoxyborohydride, which has a stronger reducing ability than Sodium Triacetylborohydride, and has better selective reduction for different functional groups. The method utilizes the reducibility of the borate, and the borate is reduced to the corresponding borohydride in the presence of hydrogen, and then reacted with an acetoxylating agent to obtain Sodium Triacetoxyborohydride.
The reaction equation is as follows:
B(OAc)3 + 4H2 → B2H6 + 3C2H5OH
B2H6 + 3(NaOAc·3H2O) → 2NaBH(OAc)3 + 3H2
The synthesis method has the advantages of mild reaction conditions, high yield, suitable for large-scale production and the like. However, since the use of hydrogen requires high pressure and special reaction equipment, the operation is relatively cumbersome.
The following are the detailed preparation steps:
3.1. Preparation of Sodium Triacetoxyborohydride:
Sodium Triacetylborohydride is an important reducing agent in this reaction, and its preparation method can refer to other literature or business journals. In simple terms, Sodium Triacetylborohydride can be obtained by reacting triphenylphosphine sodium hydride and acetic anhydride.
3.2. Preparation of methyl hydroborate:
In dry absolute ethanol, add methyl borate (0.5 mol) and stir evenly, then slowly drop in Sodium Triacetoxyborohydride (1.5 mol) and acetic acid (0.3 mol). After stirring the reaction solution for 20 minutes, it was transferred to a glass funnel and washed three times with dichloromethane to remove impurities, and finally the product was extracted and dried.
3.3. Identification of methyl hydroborate:
The products were identified and characterized by various means. For example, the product can be confirmed by nuclear magnetic resonance spectroscopy. In its 1H NMR spectrum, there are two peaks with chemical shifts of about -0.5 and -12 ppm, which are the signals of the B-H group, and other signals come from the methyl ester and acetyl groups. group. At the same time, the IR spectrum can also provide the basis for identification, and there is a B-H stretching vibration peak at about 2400 cm-1.
In conclusion, the reaction between methyl hydroborate and Sodium Triacetoxyborohydride can effectively prepare more active reducing agents. This method has the advantages of simplicity, high efficiency and high yield, and has a wide range of applications in organic synthesis.
4. Boroacetic acid method:
The borohydride acetic acid method is an emerging method for the preparation of Sodium Triacetoxyborohydride. The method utilizes the reducibility of boroacetate, reduces boroacetate to the corresponding borohydride in the presence of hydrogen, and then obtains Sodium Triacetoxyborohydride by using ammonium acetate as an acetylating agent.
The reaction equation is as follows:
B(O2C2H5)3 + 4H2 → B2H6 + 3C2H5OH
B2H6 + 3NH4OAc → NH4BH(OAc)3 + 2(NH4OAc)·H2O
NH4BH(OAc)3 + NaOAc → NaBH(OAc)3 + NH4OAc
The following are the detailed preparation steps:
4.1. Preparation of Sodium Triacetoxyborohydride:
Sodium Triacetylborohydride is an important reducing agent in this reaction, and its preparation method can refer to other literature or business journals. In simple terms, Sodium Triacetylborohydride can be obtained by reacting triphenylphosphine sodium hydride and acetic anhydride.
4.2. Preparation of boroacetic acid:
Dissolve boric acid (0.5 mol) in acetic acid (30 mL), and stir well. Then absolute ethanol (100 mL) and Sodium Triacetoxyborohydride (1.5 mol) were added, and the reaction solution was stirred for 30 min. Finally, the product was transferred to a glass funnel and washed three times with dichloromethane to remove impurities, then the product was extracted and dried.
4.3. Identification of boroacetic acid:
The products were identified and characterized by various means. For example, the product can be confirmed by NMR spectroscopy. Its 1H NMR spectrum has a peak with a chemical shift of about -10 ppm, which is the signal of the B-H group, and other signals are derived from acetic acid and acetyl groups. At the same time, the IR spectrum can also provide a basis for identification, and there is a B-H stretching vibration peak at about 2300 cm-1.
The synthesis method has the advantages of high yield, good reproducibility, and environmental protection. However, the amino acid salt and ammonium acetate used in the reaction may lead to a decrease in the surface activity of the reactant, thereby affecting its reduction performance and reaction rate.
In conclusion, Sodium Triacetoxyborohydride is an important organic synthesis reagent with broad application prospects. It can be synthesized by various methods such as cyclic tetraphenylphosphine salt method, boric acid and ethyl iodide method, hydrogenated borate method and hydrogenated boroacetic acid method. Each method has its specific advantages and disadvantages, so in the actual production process, it is necessary to choose the appropriate method according to the specific situation.