Patent Publication Number: US-2023142429-A1

Title: Process for production of new sulfolenic intermediates

Description:
The present invention relates to a new process for the production of new specific intermediates, which are preferably used in the production of vitamin A, vitamin A acetate, or β-carotene and derivatives thereof, e.g. canthaxanthin, astaxanthin or zeaxanthin. Especially to be mentioned is that the new compounds are useful as intermediates (building blocks) in the synthesis of vitamin A or β-carotene, preferably vitamin A. 
     Vitamin A or its derivatives such as Vitamin acetate 
     
       
         
         
             
             
         
       
     
     is an important ingredient for many applications. Vitamin A plays a role in a variety of functions throughout the body, such as e.g. vision process, gene transcription, immune function, bone metabolism, haematopoiesis, skin and cellular health and antioxidant function. 
     Due to the importance of vitamin A (and its derivatives) and the complexity of the synthesis thereof, there is always a need for improved processes of production. 
     The goal of the present invention was to find easily accessible compounds, which can then be used in an improved synthesis of vitamin A or its derivates, or β-carotene, preferably vitamin A (acetate). The aim was achieved by the synthesis as disclosed and described below. 
     The new intermediates, which are produced by the process according to the present invention are the compounds of formula (I) 
     
       
         
         
             
             
         
       
     
     wherein 
     R is H, or —(CO)—(CH 2 ) n CH 3 , wherein n has a value of 0-14, or 
     R is —X(C 1-4 alkyl) 3  or —X(C 6 H 5 ) 3 , wherein X is Si or Ge 
     or R is tetrahydro pyrane, isopropylmethyl ether or 2-methoxy-butylether, 
     which are ideal intermediates (especially) in the vitamin A (and/or its derivates) production. 
     How vitamin A (and/or its derivatives) are obtained is disclosed and discussed further below. 
     The compounds of formula (I), (II) and (III) have several diastereoisomeric forms. Also when not explicitly disclosed all of these forms are all claimed and disclosed by the Markush formulae of these compounds in the present patent application. 
     To obtain a compound of formula (I), the compound of formula (II) 
     
       
         
         
             
             
         
       
     
     is reacted with a compound of formula (III) 
     
       
         
         
             
             
         
       
     
     wherein 
     wherein R is H, or —(CO)—(CH 2 ) n CH 3 , wherein n has a value of 0-14, or 
     R is —X(C 1-4 alkyl) 3  or —X(C 6 H 5 ) 3 , wherein X is Si or Ge 
     or R is tetrahydro pyrane, isopropylmethyl ether or 2-methoxy-butylether. 
     Therefore the present invention relates to a process (P) for the production of a compound of formula (I) 
     
       
         
         
             
             
         
       
     
     wherein 
     R is H, or —(CO)—(CH 2 ) n CH 3 , wherein n has a value of 0-14, preferably 0-10, more preferably 0 or 1, most preferably 1, or 
     R is —X(C 1-4 alkyl) 3  or —X(C 6 H 5 ) 3 , wherein X is Si or Ge, 
     or 
     R is tetrahydro pyrane, isopropylmethyl ether or 2-methoxy-butylether, 
     characterized in that the compound of formula (II) 
     
       
         
         
             
             
         
       
     
     is reacted with a compound of formula (III) 
     
       
         
         
             
             
         
       
     
     wherein R has the same meanings as defined for the compound of formula (I). 
     Therefore the present invention also relates to a process (P′) for the production of a compound of formula (I) 
     
       
         
         
             
             
         
       
     
     wherein 
     R is H, or —(CO)—(CH 2 ) n CH 3 , wherein n has a value of 0-10. 
     Therefore the present invention also relates to a process (P″) for the production of a compound of formula (I) 
     
       
         
         
             
             
         
       
     
     wherein 
     R is H, or —(CO)—(CH 2 ) n CH 3 , wherein n has a value of 0 or 1. 
     Therefore the present invention also relates to a process (P′″) for the production of a compound of formula (I) 
     
       
         
         
             
             
         
       
     
     wherein 
     R is H, or —(CO)—(CH 2 ) CH 3 . 
     Therefore the present invention also relates to a process (P″″) for the production of a compound of formula (I) 
     
       
         
         
             
             
         
       
     
     wherein 
     R is —X(C 1-4 alkyl) 3  or —X(C 6 H 5 ) 3 , wherein X is Si or Ge. 
     Therefore the present invention also relates to a process (P′″″) for the production of a compound of formula (I) 
     
       
         
         
             
             
         
       
     
     wherein 
     R is tetrahydro pyrane, isopropylmethyl ether or 2-methoxy-butylether. 
     It is known from the prior art how to obtain the compounds of formula (II) (e.g. from Desai et al. Tetrahedron, 1992, 48, 481-490 or from Kienzle et al. Helvetica Chimica Acta, 1975, 58, 27-40.) 
     The process according to the present invention is usually carried out in the presence of a strong base such as Schlesinger base, 2,2,6,6-tetramethyl piperidine, lithium diisopropylamide, n-butyllithium, hexyllithium, tert.-butyl lithium, sec-butyllithium, metal amide (with metals such as Na, K and Cs), lithium hexamethyldisilazane, metal hydride (with metals such as Na, Mg, K and Cs), metal hydroxide (with metals such as Na, K and Cs), metal alkoxide (with metals such Na, K and Cs) or sodium hexamethyl-disilazane. 
     Therefore the present invention relates to the process (P1), which is process (P), (P′), (P″), (P′″), (P″″) or (P′″″), wherein the process is carried out in the presence of at least one strong base. 
     Therefore the present invention relates to the process (P1′), which is process (P1), wherein the at least one strong base is chosen from the group consisting of Schlesinger base, 2,2,6,6-tetramethyl piperidine, lithium diisopropylamide, n-butyllithium, hexyllithium, tert.-butyl lithium, sec-butyllithium, metal amide (wherein the metals are chosen from the group consisting of Na, K and Cs), lithium hexamethyldisilazane, metal hydride (wherein the metals are chosen from the group consisting of Na, Mg, K and Cs), metal hydroxide (wherein the metals are chosen from the group consisting of Na, K and Cs), metal alkoxide (wherein the metals are chosen from the group consisting of Na, K and Cs) and sodium hexamethyl-disilazane. 
     The process is usually carried out in an inert solvent. Preferably the solvent is a polar aprotic solvent. More preferably the solvent is chosen from the group consisting of pyridine, toluene, xylene, THF, methyl THF, or ethers (such as diethylether, 1,4-dioxane, 1,2-dimethoxyethane and crown ethers). 
     It is also possible to have a mixture of solvents, wherein one solvent can also be a nonpolar solvent (such as heptane, n-pentane, and other hydrocarbones). 
     Therefore the present invention relates to the process (P2), which is process (P), (P′), (P″), (P′″), (P″″), (P′″″), (P1) or (P1′), wherein the process is carried out in at least one inert solvent. 
     Therefore the present invention relates to the process (P2′), which is process (P2), wherein the solvent is a polar aprotic solvent. 
     Therefore the present invention relates to the process (P2″), which is process (P2) or (P4′), wherein the at least one solvent is chosen from the group consisting of pyridine, toluene, xylene, THF, methyl THF, and ethers. 
     Therefore the present invention relates to the process (P2′″), which is process (P2) or (P4′), wherein the at least one solvent is chosen from the group consisting of pyridine, toluene, xylene, THF, methyl THF, and ethers chosen from the group consisting of diethylether, 1,4-dioxane, 1,2-dimethoxyethane and crown ethers. 
     The process according to the present invention is usually carried out at low temperature. Usually a temperature range of from −100° C. to 25° C., preferably at a temperature range of from −95° C. to 5° C. 
     Therefore the present invention relates to the process (P3), which is process (P), (P′), (P″), (P′″), (P″″), (P′″″), (P1), (P1′), (P2), (P2′), (P2″) or (P2′″), wherein the process is carried out at a temperature range of from −100° C. to 25° C. 
     Therefore the present invention relates to the process (P3′), which is process (P), (P′), (P″), (P′″), (P″″), (P′″″), (P1), (P1′), (P2), (P2′), (P2″) or (P2′″), wherein the process is carried out at a temperature range of from −95° C. to 5° C. 
     The starting material, which are the compounds of formula (II) and of formula (III) can be used in equimolar amounts. But it is also possible to use an excess of one of the starting material. Usually the molar ratio of the compound of formula (II) to the compound of formula (III) goes from 1:2 to 2:1. 
     Therefore the present invention relates to the process (P4), which is process (P), (P), (P′), (P″), (P′″), (P″″), (P′″″), (P1), (P1′), (P2), (P2′), (P2″), (P2′″), (P3) or (P3′), wherein the molar ratio of the compound of formula (II) to the compound of formula (III) goes from 1:2 to 2:1. 
     The obtained products of the process according to the present invention (these are the compound of formula (I)) are new ideal intermediates. Especially in the production of vitamin A and its derivates. 
     Therefore the present invention relates to compounds of formula (I) 
     
       
         
         
             
             
         
       
     
     wherein 
     R is H, or —(CO)—(CH 2 ) n CH 3 , wherein n has a value of 0-14, or 
     R is —X(C 1-4 alkyl) 3  or —X(C 6 H 5 ) 3 , wherein X is Si or Ge, 
     or 
     R is tetrahydro pyrane, isopropylmethyl ether or 2-methoxy-butylether. 
     Preferably, the present invention relates to compounds of formula (I) 
     
       
         
         
             
             
         
       
     
     wherein R is —(CO)—(CH 2 ) n CH 3 , wherein n has a value of 0-10. 
     More preferably, the present invention relates to compounds of formula (I) 
     
       
         
         
             
             
         
       
     
     wherein R is —(CO)—(CH 2 ) n CH 3 , wherein n has a value of 0 or 1. 
     Most preferably, the present invention relates to the compound of formula (I) 
     
       
         
         
             
             
         
       
     
     wherein R is —(CO)—(CH 2 )CH 3 . 
     The following schema shows how to produce vitamin A (or derivatives thereof) can be obtained. 
     
       
         
         
             
             
         
       
     
     R has the same meanings are defined above. 
     The following example serve to illustrate the invention. The temperature is given in ° C. and all percentages are related to the weight. 
    
    
     EXAMPLES 
     Example 1: Synthesis of the Intermediate 
     3-Methyl-2-((2,6,6-trimethylcyclohex-1-en-1-yl)methyl)-2,5-dihydrothiophene 1,1-dioxide (5.65 g, 20.1 mmol; 1.0 eq), (E)-3-methyl-4-oxobut-2-en-1-yl acetate (2.95 g, 20.8 mmol; 1.03 eq) and dry tetrahydrofuran (40.0 mL) were placed in a dried four necked round bottom flask equipped with a magnetic stirrer, thermometer and condenser under an argon atmosphere. The reaction mixture was cooled to −76° C. Lithium diisopropylamide (20.0 mL, 20.0 mmol, 0.99 eq, 1 M in tetrahydrofuran/hexane, d=0.719 g/mL) was added dropwise over a period of 40 min. The reaction was stirred at −76° C. for 2 h. Subsequently, the cooling bath was removed and half saturated ammonium chloride solution (100 mL) was added. The reaction mixture was diluted with diethylether (150 mL). The aqueous layer was separated and extracted with diethylether (150 mL). The organic layers were washed with half saturated ammonium chloride solution (100 mL), water (2×100 mL) and saturated sodium chloride solution (100 mL). The combined organic layers were filtered over a plug of cotton wool. All volatiles were evaporated at 40° C. (5 mbar). 
     The crude was purified with a column chromatography (SiO2) to obtain the products in 45% yield. 
     Example 2: Synthesis of Compound IV 
     (E)-4-hydroxy-3-methyl-4-(4-methyl-1,1-dioxido-5-((2,6,6-trimethylcyclohex-1-en-1-yl)methyl)-2,5-dihydrothiophen-2-yl)but-2-en-1-yl acetate (55 mg, 0.13 mmol; 1.0 eq) and pyridine (3.0 mL) were placed in a dried two necked round bottom flask equipped with a magnetic stirrer and condenser under an argon atmosphere. The reaction mixture was heated to 100° C. for 5 h. All volatiles were evaporated under reduced pressure (50° C., 5 mbar) to obtain the product in 82% yield 
     Example 3: Synthesis of Vitamin A Acetate from Compound I 
     (E)-4-hydroxy-3-methyl-4-(4-methyl-1,1-dioxido-5-((2,6,6-trimethylcyclohex-1-en-1-yl)methyl)-2,5-dihydrothiophen-2-yl)but-2-en-1-yl acetate (product obtained from Example 1) (263 mg, 0.6 mmol; 1.0 eq) and dry toluene (5.0 mL) were placed in a dried two necked round bottom flask equipped with a magnetic stirrer and condenser under an argon atmosphere. The reaction mixture was heated to reflux for 2 h. All volatiles were evaporated under reduced pressure (40° C., 5 mbar) to obtain the product in a yield of 71%. 
     Example 4: Preparation of Retinyl Propionate 
     3-Methyl-2-((2,6,6-trimethylcyclohex-1-en-1-yl)methyl)-2,5-dihydrothiophene 1,1-dioxide (310 mg, 1.1 mmol; 1.0 eq), (E)-3-methyl-4-oxobut-2-en-1-yl propionate (190 mg, 1.2 mmol; 1.1 eq) and dry toluene (2.0 mL) were placed in a dried two necked round bottom flask under an argon atmosphere. The reaction mixture was cooled to −76° C. Lithium diidopropylamide (1.2 mL, 1.2 mmol, 1.1 eq, 1 M in tetrahydrofuran/hexane, d=0.719 g/mL) was added over a period of 7 min. The reaction mixture was stirred at −76° C. for 7 min. Subsequently the cooling bath was removed and half saturated ammonium chloride solution (5 mL) was added. The reaction mixture was diluted and extracted with toluene (10 mL). The aqueous layer was separated and extracted with toluene (10 mL). The organic layers were washed with water (2×10 mL) and saturated sodium chloride solution (1×10 mL). The combined organic layers were filtered over a plug of cotton wool. All volatiles were evaporated at 40° C. (5 mbar) until a clear yellow oil remained. 
     The oil was placed in a dried two necked round bottom flask and dissolved in toluene (5 mL) with a magnetic stirrer, condenser under an argon atmosphere. The reaction mixture was heated to reflux for 2 h. All volatiles were evaporated under reduced pressure (50° C., 5 mbar) to obtain the product (399 mg), yield=52%. 
     Example 5: Preparation of Retinyl Acetate 
     3-Methyl-2-((2,6,6-trimethylcyclohex-1-en-1-yl)methyl)-2,5-dihydrothiophene 1,1-dioxide (308 mg, 1.1 mmol; 1.0 eq), (E)-3-methyl-4-oxobut-2-en-1-yl acetate (161 mg, 1.1 mmol; 1.0 eq) and dry toluene (2.0 mL) were placed in a dried two necked round bottom flask equipped with a magnetic stirrer under an argon atmosphere. The reaction mixture was cooled to −76° C. Lithium diidopropylamide (1.2 mL, 1.2 mmol, 1.1 eq, 1 M in tetrahydrofuran/hexane, d=0.719 g/mL) was added dropwise over a period of 8 min. The reaction was stirred at −76° C. for 7 min. Subsequently, the cooling bath was removed and half saturated ammonium chloride solution (5 mL) was added. The reaction mixture was diluted with toluene (10 mL). The aqueous layer was separated and extracted with toluene (10 mL). The organic layers were washed with water (2×10 mL) and saturated sodium chloride solution (1×10 mL). The combined organic layers were filtered over a plug of cotton wool. All volatiles were evaporated at 40° C. (5 mbar). 
     The oil was placed in a dried two necked round bottom flask and dissolved in toluene (5 mL) with a magnetic stirrer under an argon atmosphere. The reaction mixture was heated to reflux for 1 h. All volatiles were evaporated under reduced pressure (40° C., 5 mbar). Purification afforded the product in 34% yield.