Background
Cyclen (1,4,7, 10-tetraazadodecane, Cyclen), a white or nearly white crystalline powder chemical. Molecular formula C8H20N4And the molecular weight is 172.28. Is an important intermediate for synthesizing the therapeutic drugs of the diagnostic kit. The cyclen and the derivatives thereof are used for removing stones in human bodies, and particularly show extremely important application values in the aspects of manufacturing contrast agents of medical imaging technologies such as nuclear Magnetic Resonance Imaging (MRI), X-ray CT, ultrasonic imaging and the like and radiopharmaceutical treatment of malignant tumors. The complex can form a stable complex with ions as a precursor of a macrocyclic chelating agent for synthesizing metal ions, particularly paramagnetic metal ions such as a complex formed with gadolinium ions, is applied to the field of medical diagnosis, does not have high toxicity caused by free ions, and has the safety characteristic. At present, the aging is more and more serious in the world, the demand of the cyclen is more and more, the compound has wide market prospect, but only a few factories produce the compound in the world at present, and the purity of the product is not high.
At present, the chemical synthesis methods of cyclen mainly comprise a Stetter synthesis method, a Richman-Atkins synthesis method, a Weisman synthesis method, a glyoxal condensation method and a diethyl oxalate synthesis method.
Stetter synthesis method
The first general method for the synthesis of macrocyclic polyamines was proposed by Stetter and Max in 1957 (Stetter, H.; Marx, J.chem.Brit.1957,607,59), which uses a condensation cyclization of a di-p-toluenesulfonamide derivative of ethylenediamine diacetoxy chloride with ethylenediamine under highly dilute conditions (about 0.001mol/L), followed by reduction and deprotection to give the desired product. The raw materials required by the method are not easy to obtain, and the method is not suitable for industrial mass preparation due to the ring closure under the high dilution condition, the reaction yield is not high, the productivity is limited, and the method is rarely adopted at present.
Richman-Atkins synthesis method
For many years, people prefer to use the Richman-Atkins method (Richman, J.E.; Atkins, T.J.J.Am.chem.Soc.1974,96,2268) to synthesize cyclen, which has become the classic method for preparing cyclen. The method uses diethyl triamine and diethanol amine to respectively prepare cycleanine through 5 steps of tosylation, salification, ring closing, protecting group removal, alkalization extraction and the like. The method has high yield and large synthesis amount, and is one of the current main ways for preparing cyclen in a laboratory. However, the method has many experimental steps, large reagent consumption for protection and deprotection, low atom utilization rate and inconvenient operation, and is not an ideal industrial synthetic route.
Weisman synthesis method
The above-described Richman-Atkins synthesis requires removal of the four p-toluenesulfonyl groups during synthesis, which is not consistent with atom economy guidelines. Having noticed this drawback, Weisman et al proposed a new method for the synthesis of cyclen (Weisman, g.r.org.chem.1997,62,4548). Namely, dithiooxamide and triethylenetetramine directly react to obtain tricyclic diamidine, and then diisobutylaluminum hydride (DIBALH) is used for carrying out double reduction to obtain cycleanine after ring expansion, wherein the total yield is 67%.
The method does not need a protecting group, is completed in two steps, has high product yield and purity, and is particularly easy to realize in a laboratory. The solvent is required in a proper amount as compared with the Richman-Atkins method, which has disadvantages in that dithiooxamide as a starting material is expensive, hydrogen sulfide is generated as a by-product in the reaction, DIBALH used in the reduction step is expensive and sensitive to moisture, and the operation requires extra care and is limited by the above factors, and which is suitable for synthesis of only a small amount.
Condensation of glyoxal
The glyoxal condensation process is a new process developed in recent years. The condensation of glyoxal water solution and triethylenetetramine is adopted to prepare cyclen (Hervre, G.tetrahedron Lett.1999,40,2517), and the common points of the two are that one or a plurality of rigid intermediates which are isomers each other are firstly obtained, and cyclen is then obtained through cyclization and deprotection steps. The method has the advantages of easily available raw materials, low cost, mild reaction conditions and simpler product purification.
The biggest problem of the route is that during the further ring closing process of the rigid intermediate and dibromoethane, the ring forming reaction is competitive with the reaction of dibromoethane and tertiary amine to form quaternary ammonium salt, and the yield is low. The amplification effect in the industrial production process is more difficult to control for the side reaction, so the strategy of forming the rigid intermediate by using the triethylenetetramine as the starting material is not suitable for the amplification production.
Diethyl oxalate synthesis method
The method has less research, and the product is obtained by adopting triethylene tetramine and diethyl oxalate to condense and close a ring (Wei, J. -F.chem.J.Chin.Univ.1997,18,658) and then reducing with diborane. The condensation and ring-closing reaction of triethylenetetramine and diethyl oxalate also has the defects that the reaction needs to be carried out at a relatively dilute concentration and is not suitable for industrial production.
The above routes have great defects in raw materials or processes, and bring certain difficulties to the industrial production of cyclen.
Disclosure of Invention
The invention aims to overcome the defect of single type of the existing cyclocyclen synthesis route, and provides a preparation method of cyclocyclen and an intermediate thereof. The preparation method has the advantages of low cost, simple and convenient operation, easy purification of intermediates and products, high yield and purity, and suitability for industrial production.
The present invention solves the above-mentioned problems by the following technical solutions.
The invention provides a preparation method of a compound shown as a formula 4, which comprises the following steps: in water, carrying out a reduction reaction on a compound shown as a formula 3 and hydrazine hydrate as shown in the specification;
wherein, X is phosphoric acid or sulfuric acid;
when X is phosphoric acid, n is 4/3;
when X is sulfuric acid, n is 2.
In the preparation method of the compound shown in the formula 4, X is preferably sulfuric acid.
In the preparation method of the compound shown in the formula 4, the water and the hydrazine hydrate can be added in the form of hydrazine hydrate aqueous solution. The hydrazine hydrate aqueous solution can be a hydrazine hydrate aqueous solution with the mass fraction which is conventional in the field, preferably a hydrazine hydrate aqueous solution with the mass fraction of 50-80%, for example a hydrazine hydrate aqueous solution with the mass fraction of 50% or 80%.
In the preparation method of the compound shown in the formula 4, the molar ratio of the hydrazine hydrate to the compound shown in the formula 3 can be a molar ratio which is conventional in the field, and is preferably 3:1-5:1, such as 3:1 or 5: 1.
In the preparation method of the compound represented by the formula 4, the temperature of the reduction reaction may be a temperature conventional in the art, preferably 60 to 100 ℃, more preferably 80 to 90 ℃, for example 90 ℃.
In the preparation method of the compound represented by formula 4, the progress of the reduction reaction can be monitored by means conventional in the art (such as TLC, HPLC, GC or NMR, preferably GC), and the time of the reduction reaction is preferably 12 to 96 hours, more preferably 12 to 30 hours, such as 12 hours.
The preparation method of the compound shown in the formula 4 can further comprise the following steps: in an organic solvent, carrying out a salt forming reaction on a compound shown as a formula 2 and X as shown in the specification;
wherein n and X are as defined above.
In the salt forming reaction, the organic solvent may be an organic solvent which is conventional in the art, preferably one or more of halogenated hydrocarbon solvents, nitrile solvents, ketone solvents, ester solvents and alcohol solvents, and more preferably an alcohol solvent. The halogenated hydrocarbon solvent is preferably dichloromethane. The nitrile solvent is preferably acetonitrile. The ketone solvent is preferably acetone. The ester solvent is preferably ethyl acetate. The alcohol solvent is preferably one or more of methanol, ethanol, propanol and butanol, and more preferably ethanol.
In the salt-forming reaction, when X is phosphoric acid, the phosphoric acid can be added in the form of a phosphoric acid aqueous solution. The phosphoric acid aqueous solution can be phosphoric acid aqueous solution with mass fraction which is conventional in the field, preferably phosphoric acid aqueous solution with mass fraction of 65-85%, and more preferably phosphoric acid aqueous solution with mass fraction of 85%.
In the salt-forming reaction, X is preferably sulfuric acid. The sulfuric acid may be added in the form of an aqueous sulfuric acid solution. The sulfuric acid aqueous solution can be a sulfuric acid aqueous solution with a mass fraction which is conventional in the field, preferably an 80-98% sulfuric acid aqueous solution, and more preferably a 98% sulfuric acid aqueous solution.
In the salt-forming reaction, the molar ratio of the X to the compound represented by the formula 2 can be a molar ratio which is conventional in the art, and is preferably 1:1 to 6:1, such as 2.15:1, 2.37:1 or 6: 1.
In the salt-forming reaction, the volume-to-mass ratio of the organic solvent to the compound represented by the formula 2 can be a volume-to-mass ratio conventional in the art, and is preferably 1 to 50mL/g, more preferably 1 to 20mL/g, further preferably 5 to 20mL/g, further preferably 15 to 20mL/g, for example 17.86 mL/g.
In the salt-forming reaction, the temperature of the salt-forming reaction may be a temperature conventional in the art, and is preferably-20 to 20 ℃, more preferably-10 to 10 ℃, further preferably 0 to 10 ℃, for example 0 ℃.
In the salt-forming reaction, the progress of the salt-forming reaction can be monitored by means conventional in the art (e.g., TLC, HPLC, GC, or NMR, preferably GC), and the time of the salt-forming reaction is preferably 5 to 40 hours, more preferably 5 to 10 hours, e.g., 5 hours.
The work-up of the salt-forming reaction may be a work-up conventional in the art, which comprises the following steps: and filtering the reaction solution, washing a filter cake, and drying. The solvent for washing is preferably an alcoholic solvent, such as ethanol.
The preparation method of the compound shown in the formula 4 can further comprise the following steps:
(1) carrying out addition reaction on a compound shown as a formula 1 and glyoxal in the presence of benzotriazole by using an organic solvent and water to obtain a reaction solution 1;
(2) in the presence of a reducing agent, carrying out reduction reaction on the reaction solution 1 in the step (1);
in the step (1), the organic solvent may be an organic solvent conventional in the art, preferably one or more of an alcohol solvent, an ether solvent, an ester solvent, a nitrile solvent, a halogenated hydrocarbon solvent, a ketone solvent and an aromatic hydrocarbon solvent, and more preferably an alcohol solvent. The alcohol solvent is preferably one or more of ethanol, methanol and isopropanol, and more preferably ethanol. The ether solvent is preferably methyl tert-butyl ether. The ester solvent is preferably ethyl acetate and/or isopropyl acetate. The nitrile solvent is preferably acetonitrile. The halogenated hydrocarbon solvent is preferably dichloromethane. The ketone solvent is preferably acetone. The aromatic hydrocarbon solvent is preferably toluene and/or xylene.
In the step (1), the water and the glyoxal may be added in the form of aqueous glyoxal solution, which may be aqueous glyoxal solution with a mass fraction conventional in the art, preferably aqueous glyoxal solution with a mass fraction of 10% -40%, for example, aqueous glyoxal solution with a mass fraction of 40%.
In step (1), the molar ratio of the glyoxal to the compound of formula 1 may be a molar ratio conventional in the art, preferably 2:1 to 8:1, more preferably 2:1 to 3:1, for example 2: 1.
In the step (1), the molar ratio of the benzotriazole to the compound shown in formula 1 may be a molar ratio which is conventional in the art, and is preferably 2:1-8:1, more preferably 2:1-3:1, such as 2: 1.
In the step (1), the volume-to-mass ratio of the organic solvent to the compound represented by the formula 1 may be a volume-to-mass ratio conventionally used in the art, and is preferably 3 to 30mL/g, more preferably 3 to 9mL/g, further preferably 3 to 6mL/g, for example 4 mL/g.
In step (1), the temperature of the addition reaction may be a temperature conventional in the art, preferably from-20 ℃ to the reflux temperature of the organic solvent under normal pressure, more preferably from 0 to 20 ℃, for example, 0 ℃.
In step (1), the addition reaction may be monitored by means conventional in the art (e.g. TLC, HPLC, GC or NMR, preferably GC), preferably for a period of 3 to 72 hours, more preferably 3 to 12 hours, for example 3 hours.
In step (2), the reducing agent may be a reducing agent conventional in the art, preferably one or more of sodium borohydride, lithium aluminum hydride, hydrogen gas, hydrazine hydrate, ammonium formate, formic acid and triethylamine formic acid azeotrope, more preferably sodium borohydride.
In step (2), the molar ratio of the reducing agent to the compound represented by formula 1 in step (1) may be a molar ratio conventional in the art, preferably 2:1 to 20:1, more preferably 2:1 to 4:1, for example 2: 1.
In the step (2), the temperature of the reduction reaction may be a reaction temperature conventional in the art, preferably 0 ℃ to the reflux temperature of the organic solvent under normal pressure, more preferably 0 to 20 ℃, for example, 0 ℃.
In step (2), the reduction may be monitored by means conventional in the art (e.g. TLC, HPLC, GC or NMR, preferably GC), preferably for a period of 3 to 72 hours, more preferably 3 to 12 hours, for example 3 hours.
The work-up operation of the reduction reaction may be a work-up operation conventional in the art, comprising the following steps: removing organic solvent, removing water, filtering, and concentrating the filtrate. The method of removing the organic solvent is preferably concentration, more preferably concentration under reduced pressure/atmospheric pressure. Before the organic solvent is removed, a filtration operation is preferably further included. The water removal is preferably carried out by adding an organic solvent. The water diversion operation can be the operation conventional in the field, and the water diversion under the normal pressure reflux is preferred. The organic solvent added in the water separation operation is preferably an aromatic hydrocarbon solvent such as toluene. After the water removal is finished, the method can further comprise a temperature reduction step, wherein the temperature reduction is preferably carried out to 20-30 ℃, for example 20 ℃. Preferably, before concentrating the filtrate, the operation of washing the filter cake can be further included. The solvent for washing is preferably an aromatic hydrocarbon solvent such as toluene. The number of washing is preferably 1 to 2.
The invention provides a preparation method of a compound shown as a formula 5, which comprises the following steps:
(1) preparing a compound shown in a formula 4 according to any one method;
(2) carrying out neutralization reaction on the compound shown in the formula 4 obtained in the step (1) and alkali as shown in the specification;
wherein n and X are as defined above;
in the preparation method of the compound shown in the formula 5, in the step (1), the reduction reaction conditions and operation are the same as those of the reaction.
In the preparation method of the compound represented by the formula 5, in the step (2), the base can be a base conventional in the art, preferably an alkali metal hydroxide, and more preferably sodium hydroxide.
In the preparation method of the compound shown in the formula 5, in the step (2), other conditions and parameters of the neutralization reaction are the same as those of the reaction in the field.
In the preparation method of the compound represented by the formula 5, in the step (2), the post-treatment of the neutralization reaction may be a post-treatment conventional in the art, and comprises the following steps: concentrating the reaction solution, adding a solvent to extract a concentrate, filtering an organic phase, concentrating, and recrystallizing to obtain the compound. The concentration is preferably carried out under reduced pressure. The solvent is preferably an aromatic hydrocarbon solvent, such as toluene. The solvent for recrystallization is preferably an aromatic hydrocarbon solvent and/or an alkane solvent, the aromatic hydrocarbon solvent is preferably toluene, and the alkane solvent is preferably n-heptane.
The invention also provides a preparation method of the compound shown in the formula 2, which comprises the following steps:
(1) carrying out addition reaction on a compound shown as a formula 1 and glyoxal in the presence of benzotriazole by using an organic solvent and water to obtain a reaction solution 1;
(2) the reaction solution 1 obtained in the step (1) is subjected to a reduction reaction in the presence of a reducing agent, and the post-treatment comprises the steps of: removing organic solvent, removing water, filtering, and concentrating; the water removal is water diversion water removal;
in the preparation method of the compound shown as the formula 2, in the step (1), the conditions and operation of the addition reaction are the same as those of the reaction.
In the preparation method of the compound shown in the formula 2, in the step (2), the reduction reaction conditions and operation are the same as those of the reaction.
In the preparation method of the compound represented by the formula 2, in the step (2), the method for removing the organic solvent may be a method conventional in the art, and preferably concentration under reduced pressure or concentration under normal pressure is performed.
In the preparation method of the compound represented by the formula 2, before removing the organic solvent in the step (2), a filtration operation is preferably further included, and the filtration conditions and methods may be those conventional in the art, such as reduced pressure filtration or atmospheric pressure filtration.
In the preparation method of the compound shown in the formula 2, in the step (2), the water diversion operation can be a conventional operation in the field, and preferably performs water diversion under reduced pressure reflux or water diversion under normal pressure reflux, and more preferably performs water diversion under normal pressure reflux. The organic solvent used for the water separation is preferably an aromatic hydrocarbon solvent, and more preferably toluene.
In the preparation method of the compound shown as the formula 2, in the step (2), after the water removal is finished, a cooling step can be further included, and the cooling is preferably cooled to 20-30 ℃, for example, 20 ℃.
In the preparation method of the compound represented by the formula 2, in the step (2), the filtration operation may be an operation conventional in the art, such as reduced pressure filtration or atmospheric pressure filtration.
In the preparation method of the compound shown in the formula 2, in the step (2), after the filtration is finished, the washing operation can be further included. The solvent for washing is preferably an aromatic hydrocarbon solvent such as toluene. The number of washing is preferably 1 to 2.
In the preparation method of the compound represented by the formula 2, in the step (2), the concentration operation may be an operation conventional in the art, for example, concentration under reduced pressure or concentration under normal pressure.
The invention also provides a purification method of the compound shown as the formula 2, which comprises the following steps: a mixture comprising a compound represented by formula 2, an organic solvent and water is treated as follows: removing organic solvent, removing water, filtering, and concentrating; the water removal is water diversion water removal;
in the method for purifying the compound represented by formula 2, the method for removing the organic solvent may be a method conventional in the art, and preferably concentration under reduced pressure or concentration under normal pressure.
In the method for purifying the compound represented by formula 2, before removing the organic solvent, a filtration operation is preferably further included, and the filtration conditions and method may be those conventional in the art, such as reduced pressure filtration or atmospheric pressure filtration.
In the purification method of the compound shown in the formula 2, the water diversion operation can be a conventional operation in the field, and preferably carries out water diversion under reduced pressure reflux or water diversion under normal pressure reflux, and more preferably carries out water diversion under normal pressure reflux. The organic solvent used for the water separation is preferably an aromatic hydrocarbon solvent, and more preferably toluene.
In the purification method of the compound shown in the formula 2, after the water removal is finished, a cooling step can be further included, and the cooling is preferably cooled to 20-30 ℃, for example, 20 ℃.
In the method for purifying the compound represented by the formula 2, the filtration operation may be an operation conventional in the art, such as reduced pressure filtration or atmospheric pressure filtration.
In the method for purifying the compound represented by the formula 2, after the filtration is finished, preferably, a washing operation may be further included. The solvent for washing is preferably an aromatic hydrocarbon solvent such as toluene. The number of washing is preferably 1 to 2.
In the purification method of the compound represented by the formula 2, the concentration operation may be an operation conventional in the art, such as concentration under reduced pressure or concentration under normal pressure.
The invention also provides a compound shown as a formula 4-1 or a formula 4-2,
the above preferred conditions can be arbitrarily combined to obtain preferred embodiments of the present invention without departing from the common general knowledge in the art.
In the present invention, "° c" means "degrees celsius", unless otherwise specified; "h" means "hour".
In the present invention, the room temperature means 10 to 40 ℃ unless otherwise specified.
The reagents and starting materials used in the present invention are commercially available unless otherwise specified.
The positive progress effects of the invention are as follows: the preparation method has the advantages of low cost, simple and convenient operation, easy purification of intermediates and products, high yield and purity, and suitability for industrial production.
Detailed Description
The invention is further illustrated by the following examples, which are not intended to limit the scope of the invention. The experimental methods without specifying specific conditions in the following examples were selected according to the conventional methods and conditions, or according to the commercial instructions.
Example 1
100 g of triethylenetetramine and 163 g of benzotriazole are dissolved in 400mL of ethanol, 200 g of 40% glyoxal aqueous solution is dropwise added at 0 ℃, the mixture is stirred for 3 hours at 0 ℃, and the reaction is controlled to be qualified. 52 g of sodium borohydride was added at 0 ℃ and stirred for 3 hours. After the reaction is controlled to be qualified, filtering to remove insoluble salt, concentrating the filtrate to remove ethanol, adding 600mL of toluene, heating to raise the temperature for normal-pressure reflux water separation, completely removing the water, cooling to 20 ℃, filtering to remove insoluble solid benzotriazole (used for recovery, the recovery rate is 92%), washing the filter cake once with 100mL of toluene, combining the filtrates, and concentrating the filtrate under reduced pressure until no obvious fraction is distilled off to obtain the compound of the formula 2, wherein the compound of the formula 2 is 100 g of pale yellow oily substance, the yield is 75%, and the content is about 70%.1H NMR(CDCl3,400MHz):3.087(s,2H),2.959-2.875(m,8H),2.635-2.487(m,8H).13C NMR(CDCl3,125.8MHz):77.43,51.04,50.26.GC-MS:194.
Example 2
56 g of the compound of the formula 2 (in 100% purity) are dissolved in 1000mL of ethanol, cooled to 0 ℃ and 68.6 g of 98% sulfuric acid are added dropwise, and the mixture is stirred at 0 ℃ for 5 hours. Filtering, washing a filter cake by using ethanol, and drying the filter cake to obtain 107 g of the compound shown in the formula 3-1 with the yield of 95%. Purity of compound 3-1 is not less than 96%, total nitrogen: 14.45 percent.
Example 3
56 g of the compound of the formula 2 (in 100% purity) are dissolved in 1000mL of ethanol, 173 g of 98% sulfuric acid are added dropwise, cooling to 0 ℃ and stirring for 5 hours at 0 ℃. Filtering, washing a filter cake by using ethanol, and drying the filter cake to obtain 108 g of the compound shown in the formula 3-1 with the yield of 95%.
Example 4
56 g of the compound of the formula 2 (in 100% purity) are dissolved in 1000mL of ethanol, cooled to 0 ℃ and 72 g of 85% phosphoric acid are added dropwise, and the mixture is stirred at 0 ℃ for 5 hours. Filtering, washing a filter cake with ethanol, and drying the filter cake to obtain 89 g of a compound shown in the formula 3-2, wherein the yield is 95%, the purity of the compound 3-2 is not less than 96%, and the total nitrogen: 17.50 percent.
Example 5
100 g of a compound of formula 3-1 (100% pure) in waterDissolving in 80 g of 80% hydrazine hydrate, heating to 90 ℃, and keeping the temperature for 12 hours. After the completion of the neutralization reaction, 31 g of sodium hydroxide was added, followed by removing the aqueous phase by concentration under reduced pressure, and 200mL of toluene was added to extract the concentrated residue. Filtering to remove insoluble substances, concentrating the filtrate, adding 200mL of toluene for recrystallization, filtering to remove mother liquor, and drying the filter cake to obtain 33 g of white cyclen product, wherein the yield is 75% and the purity is more than 99.5%.1H NMR(CDCl3,400MHz):2.485-2.435(d,16H),1.832(s,4H).13C NMR(CDCl3,125.8MHz):45.9.GC-MS:172.
Example 6
100 g of the compound of formula 3-1 (in 100% purity) was dissolved in 128 g of 50% hydrazine hydrate, heated to 90 ℃ and incubated for 12 hours. After the completion of the neutralization reaction, 31 g of sodium hydroxide was added, followed by removing the aqueous phase by concentration under reduced pressure, and 200mL of toluene was added to extract the concentrated residue. Filtering to remove insoluble substances, concentrating the filtrate, adding 200mL of toluene for recrystallization, filtering to remove mother liquor, and drying the filter cake to obtain 35 g of white cyclen product, wherein the yield is 79 percent, and the purity is more than 99.5 percent.
Example 7
100 g of the compound of formula 3-1 (in 100% purity) was dissolved in 48 g of 80% hydrazine hydrate, heated to 90 ℃ and incubated for 12 hours. After the completion of the neutralization reaction, 31 g of sodium hydroxide was added, followed by removing the aqueous phase by concentration under reduced pressure, and 200mL of toluene was added to extract the concentrated residue. Filtering to remove insoluble substances, concentrating the filtrate, adding 200mL of toluene for recrystallization, filtering to remove mother liquor, and drying the filter cake to obtain 32 g of white cyclen product, wherein the yield is 73% and the purity is more than 99.5%.
Example 8
100 g of the compound of formula 3-2 (in 100% purity) are dissolved in 80 g of 80% hydrazine hydrate, the temperature is raised to 90 ℃ and the incubation is carried out for 12 hours. After the end of the neutralization reaction, 40 g of sodium hydroxide were added, followed by removal of the aqueous phase by concentration under reduced pressure, and extraction of the residue by addition of 200mL of toluene. Filtering to remove insoluble substances, concentrating the filtrate, adding 200mL of toluene for recrystallization, filtering to remove mother liquor, and drying the filter cake to obtain 29 g of white cyclen product, wherein the yield is 55%, and the purity is more than 99.5%.
Comparative example 1
87 g of the starting compound (100% purity) are dissolved in 80 g of 80% hydrazine hydrate, the temperature is raised to 90 ℃ and the incubation is carried out for 12 hours. After the completion of the neutralization reaction, 31 g of sodium hydroxide was added, followed by removing the aqueous phase by concentration under reduced pressure, and 200mL of toluene was added to extract the concentrated residue. Filtering to remove insoluble substances, concentrating the filtrate, adding 200mL of toluene for recrystallization, filtering to remove mother liquor, and drying the filter cake to obtain 19 g of white cyclen product with the yield of 43%.
Comparative example 2
The following compound 2 was synthesized with reference to the method in patent US 7659393B.
10g (68.4mmol) of triethylenetetramine and 16.3g (136.7mmol) of benzotriazole are dissolved in 200mL of water, cooled to 2 ℃ and 80mL of a methanolic glyoxal solution are slowly added dropwise thereto (19.86 g (136.7mmol) of an aqueous glyoxal solution are added to 80mL of methanol). After the dropwise addition, the mixture was warmed to room temperature and stirred for 4 hours. Thereafter, 5.18g (136.7mmol) of sodium borohydride was added in portions, and stirred at room temperature for 2 hours. After completion of the reaction, methanol was distilled off, and 13g of potassium hydroxide was added to the reaction system. The mixture was extracted with chloroform (400 mL. times.3), and the organic phase was dried over anhydrous magnesium sulfate. The solvent was removed to give compound 2 as a yellow oil (9g, yield 68%, content: about 70%).
In the actual operation process, the extraction process is easy to generate emulsification phenomenon, difficult to stratify, large in product loss, complex in operation, long in time consumption, and difficult to recycle benzotriazole.