JPH0625139B2 - 1-benzyl-2-phenylimidazole and method for synthesizing the same - Google Patents

Description

TECHNICAL FIELD The present invention relates to 1-benzyl-2-phenylimidazole (hereinafter abbreviated as 1B2PZ), and 2-phenylimidazole (hereinafter abbreviated as 2PZ) and tribenzylborate. The present invention relates to a method of synthesizing by heating in the presence of a mineral acid.

1B2PZ obtained by the method of the present invention is 2-phenyl-4 (5) -benzyl-5 (4) -hydroxymethylimidazole useful as an epoxy resin curing agent (Japanese Patent Publication No. 56-11).
703) and 2-phenyl-1,4-dibenzylimidazole as starting materials.

2. Description of the Related Art As a method for benzylating imidazole, a method of reacting imidazole with benzyl alcohol
51-105060, 51-105061 and 52-131577) There is a problem to be solved by the invention 2 An acceptor of PZ and HCl is dissolved in a suitable solvent (which does not have active hydrogen), It was found that the above reaction method of adding benzyl chloride dropwise thereto had the following drawbacks.

That is, in addition to the main reaction in which 2PZ reacts with benzyl chloride to give 1B2PZ, a side reaction in which 1B2PZ generated in turn reacts with benzyl chloride to give 1,3-dibenzyl-2-phenylimidazolium chloride is also generated. So 1
The yield of B2PZ is significantly reduced. In addition, the reaction rate of the side reaction is larger than the reaction rate of the main reaction.
It cannot be stopped at the stage of B2PZ production, and a large amount of unnecessary imidazolium chloride is by-produced.

Explaining this with the reaction formula, the main reaction Side reaction It is a problem to be solved by the present invention to derive a new method for synthesizing 1B2PZ that solves such a difficulty.

Means for Solving the Problems In view of such circumstances, the present inventors have earnestly studied, and as a result, 2
It was found that 1B2PZ can be obtained by heating PZ with tribenzyl borate in the presence of a certain mineral acid to derive the present invention.

Hereinafter, embodiments of the present invention will be described. The present invention can be shown as a reaction formula as follows.

HA represents mineral acid.

In the above reaction, the mineral acid should be used in at least an equimolar amount to 2PZ, and an equimolar amount or excess of the mineral acid does not interfere with this reaction.

As the mineral acid, any of hydrogen chloride, hydrogen bromide, hydrogen iodide, orthophosphoric acid, phosphorous acid, hypophosphoric acid, hypophosphorous acid, pyrophosphoric acid, trimetaphosphoric acid, tetrametaphosphoric acid, etc. may be used. it can. As the mineral acid generator, phosphorus oxyhalide (POX ₃ ), phosphorus halide (PX ₃ and P
X ₅ ), phosphoric anhydride, phosphorous anhydride and the like can be used in the same manner as the mineral acid. Further, a mineral acid salt that generates a mineral acid in the reaction can be used in the same manner as the mineral acid. In this case, the mineral acid salts include orthophosphoric acid, phosphorous acid, hypophosphoric acid, hypophosphorous acid, pyrophosphoric acid, trimetaphosphoric acid, and tetrametaphosphoric acid ammonium salt, sodium salt, potassium salt, calcium salt, barium salt. Either salt or magnesium salt can be used. Particularly preferred is orthophosphoric acid or a salt thereof, which can be obtained at low cost.

A wide variety of phosphoric acids and their salts can be used in the present invention, as described above. It is easily considered that the reason is that each of the mineral acids and their salts change upon heating and can change into another form of mineral acid or its salt. Toshizo Chitani: New edition Inorganic Chemistry, Nakamaki, 702
According to p. 730 (Sangyo Tosho Co., Ltd., 1973), for example, anhydrous phosphoric acid (P ₂ O ₅ ) reacts with water and reacts with orthophosphoric acid (H ₃ P
O ₄ ) and phosphorous acid (H ₃ PO ₃ ) are given. If water is insufficient, trimetaphosphoric acid (H ₃ P ₃ O ₉ ) and tetrametaphosphoric acid (H ₄ P ₄ O ₄
Give O ₁₂ ). Orthophosphoric acid releases water at 200 to 300 ° C to give pyrophosphoric acid (H ₄ P ₂ O ₇ ), and pyrophosphoric acid further releases water to become polyphosphoric acid and polyphosphoric acid also releases water to give polymetaphosphoric acid. Acid (HPO ₃ ) _n . All of this series of reactions is reversible. Hypophosphoric acid (H ₄ P ₂ O ₆ ) reacts with water to give orthophosphoric acid and phosphorous acid. Phosphorus trichloride (PC
l ₃ ) reacts with water to give phosphorous acid. Phosphorous acid reacts with water to give orthophosphoric acid.

The first salt of orthophosphoric acid releases water by heating to give the first salt of polymetaphosphoric acid (MPO ₃ ) _n . The second salt of orthophosphoric acid also gives the second salt of pyrophosphoric acid (M ₂ P ₂ H ₂ O ₇ ), and the second salt of orthophosphoric acid consisting of ammonium and alkali releases ammonia to give the second salt of metaphosphoric acid. This gives 1 salt (MPO ₃ ) _n .

From the above explanation, even if a specific phosphoric acid or a salt thereof is used as a mineral acid necessary for the practice of the present invention, they are heated during the reaction, and they also deal with the ingress and egress of water. It can be said that it is unclear whether or not the original shape is maintained. In other words, it is not clear whether it is changed to another phosphoric acid or its salt.

Tribenzylborate Is 1 mol of boric acid (H ₃ BO ₃ ) and 3 mol or more of benzyl alcohol heated at 100 ℃ or higher, and the generated water is removed from the system in the form of azeotrope [bp98 ℃, water 91wt%]. After that, the residue is distilled under reduced pressure to obtain bp ₃ 198.
It is a colorless liquid at ~ 205 ° C.

In the method of reacting 2PZ with tribenzylborate, the generated water is fixed in the form of boric acid, so that reduced pressure is not particularly required.

In the method of the present invention, heating is performed at 220 to 300 ° C., and the reaction is completed in 1 to 4 hours. When the reaction mixture is neutralized with an aqueous solution of alkali (for example, caustic alkali or ammonia), the mineral acid is transferred to the aqueous solution, and 1B2PZ, unreacted 2PZ and side reaction products float as an oil layer. Isolation and purification are performed to obtain 1B2PZ.

The side reaction products of this reaction are 1,4-dibenzyl-2-phenylimidazole and 2-phenyl-4-benzylimidazole, but their production amounts are small and only secondary.

The properties of 1B2PZ obtained by the method of the present invention are shown below.

1-benzyl-2-phenylimidazole itself
Melting point of ZnCl ₂ complex: 216 to 218 ° C. (MeOH) NMR (CDCl ₃ -TMS): δ 7.54, d (J = 6 Hz), 2H; 7.4 to 6.9, m, 10H;
5.21, S, 2H Mass (m / e): 235,234 (M ⁺ ), 143,91,76,65 Examples 1 to 14 As shown in Table 1, 2PZ, tribenzyl borate and ammonium phosphate, phosphorous acid, hydrochloric acid, pyrophosphoric acid, sodium phosphate, calcium phosphate or magnesium phosphate are reacted according to respective predetermined amounts and respective reaction conditions. ,
The resulting reaction mixture is neutralized with NaOH, washed with water, dried and then TL
C was inspected. The results are shown in Table 2.

In addition, 1B4B2PZ represents 1,4-dibenzyl-2-phenylimidazole, and 2P4BZ represents 2-phenyl-4-benzylimidazole.

Example 15 0.7 mol of 2PZ (100.8 g), 0.7 mol of NH ₄ H ₂ PO ₄ (64.4 g)
And tribenzyl-borate (0.24 mol, 80.0 g) were heated at 250 ° C. for 4 hours under normal pressure, the reaction mixture was neutralized with sodium hydroxide methanol solution, methanol was distilled off, and the residue was washed with water. Subject it to vacuum distillation,
Crude 1B2PZ (bp ₄ 200-206 ℃) 0.47 mol (110g) (6
7 mol% yield) was obtained. As a side reaction product, 19 g of a fraction (mixture of 2PZ and 1B2PZ) of bp ₄ to 200 ° C. and bp ₄ 206 to 265 were used.
℃ fraction (mixture of 1B2PZ and 1B4B2PZ) 14.0
got g.

Example 16 2PZ 0.13 mol (18.7 g), orthophosphoric acid 0.13 mol (12.7 g)
And 0.13 mol (42.9 g) of tribenzyl-borate were heated at 280 ° C. under normal pressure for 1 hour, and then the reaction system was subjected to a reduced pressure of 5 mmHg for 30 minutes at that temperature, and then the contents were treated with sodium hydroxide methanol solution. After neutralization and evaporation of methanol, the residue was washed with water and subjected to vacuum distillation to give crude 1
0.06 mol (14.3 g) (46 mol% yield) of B2PZ (bp ₅ 162 to 175 ° C.) was obtained. Also as a side reaction products bp ₇ 200 to 250 fraction ℃ (crude 1B4B2PZ) 17.0g.

Examples 17 to 20 The respective starting materials shown in Table 3 were reacted according to respective predetermined amounts and respective reaction conditions, the contents were neutralized with a sodium methanol solution, methanol was distilled off, and then the residue was washed with water and washed with water. Table 4 shows the results of gas chromatography of the above.

The measurement conditions of gas chromatography were as follows.

This equipment: Shimadzu gas chromatograph “GC-15A (PTF)” Numerical processing equipment: Integrator “C-R15A” Glass column: φ3.0mm × 2m Filler: 2% Silicon 0V-17on Uniport HPS (80/100 mesh) ), SILY-8 treated product heating conditions: 10 ° C. / min, one hundred and forty to two hundred eighty ° C. detector: FID, H ₂ 40m / min, air 500 meters / min carrier gas: N _2, 50 m / min

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Claims (2)

[Claims] 1. Structural formula 1-benzyl-2-phenylimidazole represented by. 2. 2-Phenylimidazole and structural formula The method for synthesizing 1-benzyl-2-phenylimidazole, which comprises heating tribenzyl-borate represented by the formula (1) under heating in the presence of a mineral acid, a mineral acid generator or a mineral acid salt, and neutralizing the mixture with an alkali.