With ammonium hydroxide In ethanol at 110℃; Flow reactor
General procedure: Diethyl 2,6-dimethyl-4-phenyl-1,4-dihydropyridine-3,5-dicarboxylate (4a). EtOH solution (3 mL) ofbenzaldehyde (0.67 M) mixed with ethyl acetoacetate (1.34 M) and the 25percent aqueous NH3 (3 mL) wererespectively transferred into gas-tight syringe 1 and syringe 2. The syringes were placed in a LongerLSP02-1B syringe pump which was set to deliver the reactants into the mixer at identical flow rate of 6.7μL/min. The reaction mixture was then allowed to flow through a stainless steel tube reactor which wasdipped in a 110 C oil bath. The output mixture was collected in a cooled sample vial. After reactioncompletion, rinsed the reactor with ethanol to collect all of the reactant solution and then concentratedunder vacuum. The residue was subjected to silica gel column chromatography with Pet-EA (5:1) aseluent to give 4a (612mg, 93percent yield).
With ammonium acetate In neat (no solvent) at 55℃; for 3 h; Green chemistry
General procedure: Polyhydroquinolines and DihydropyridinesA mixture of aldehyde (1 mmol), β-dicarbonyl compound (1or 2 mmol), NH4OAc (2.5 mmol), dimedone (1 mmol, whenused), and SBA-15/NHSO3H (5 molpercent) was stirred at 55 °C.After complete disappearance of starting material asindicated by TLC, the resulting mixture was diluted with hotEtOAc (10 mL) and filtered. The catalyst was completelyrecovered from the residue
With iron supported on copper/Zeolite Socony Mobil-5 nanocatalyst In water at 20℃; Sonication
General procedure: In a typical experiment, aromatic aldehyde (1 mmol), bketoester(2 mmol), ammonium acetate (1 mmol), and Fe-Cu/ZSM-5 (3 wtpercent) in 2 ml water were introduced in a 20-mL heavy-walled pear-shaped two-necked flask with nonstandard-tapered outer joint. The flask was attached to a12-mm tip diameter probe, and the reaction mixture was sonicated at ambient temperature at 20 percent power of the processor. After completion of the reaction (monitored byTLC, within 5–8 min), the solid product was filtered,washed with water and ethanol, dried, and recrystallized from ethanol. The supported reagent was washed thrice with water and ethanol and dried under vacuum before reuse.
Reference：
[1] Journal of the Iranian Chemical Society, 2016, vol. 13, # 2, p. 267 - 277
4
[ 104-88-1 ]
[ 105-45-3 ]
[ 73257-49-5 ]
Yield
Reaction Conditions
Operation in experiment
95%
at 80℃; for 0.3 h;
General procedure: A mixture of the alkyl or aryl aldehyde (1 mmol), -dicarbonyl(2 mmol) and ammonium acetate (1.5 mmol) in the presence ofFe3O4NPs (0.024 g, equal to 10 molpercent) was heated at 80C, withstirring. The progress of the reaction was monitored by TLC (elu-ent: EtOAc:n-hexane). After completion of the reaction, the mixturewas cooled to room temperature and then ethanol was added tothe resulting mixture and separated Fe3O4NPs by a normal mag-net. After evaporation of solvent, the solid product was filtered andrecrystallized from ethanol to give the pure products in 72–95percentyields based on the starting aldehyde.
95%
With C23H3BF16N2O; ammonium acetate In toluene at 100℃; for 10 h;
In a 100 mL single-necked flask, 0.01 molpercent of Lewis acid-base bifunctional catalyst I was added (where Rf = CF3R1,R2, R3, R4, R5, R6 = F), 0.1 mol of p-chlorobenzaldehyde (R7 = 4-Cl-Ph), 0.1 mol of methyl acetoacetate (R8 = Me;Me), 0.1 mol of ammonium acetate, 10 mL of toluene, and the reaction was stirred at 100 ° C for 10 hours. TLC followed the reaction to complete the reaction. anti-The yield of the product II (R7 = 4-Cl-Ph; R8 = Me; R9 = Me) was 95percent; the catalyst system was reused 10 timesAfter its catalytic performance did not decline
94%
for 2.25 h; Heating; Green chemistry
General procedure: A mixture of aldehyde 1 (1 mmol), 1,3-dicarbonyl compound 2 (2 mmol), and nitrogen source 3 (3 mmol) were mixed and heated in the presence of a low-melting sugar mixture.The progress of the reaction was monitored by thin-layer chromatography (TLC) using n-hexane–ethyl acetate (7:3) as the solvent system. The Rf values of the product spots ranged from 0.5 to 0.6. After completion of the reaction, water was added to the reaction mixture to obtain the solid product as a precipitate. In cases where the product was obtained as a melt, several washings with water followed by bicarbonate solution gave crystalline products. The solids were filtered and washed with cold water. In most of the cases, the product obtained was pure, and when impure, the product was recrystallized from hot ethanol. Further two products were obtained as oils (Table 5, entries 4w and 4x). These products were extracted with ethyl acetate and dried over anhydrous Na2SO4. Evaporation of the solvent gave the pure product as an oil.
91%
at 100℃; for 0.25 h; Green chemistry
General procedure: To a glassy reactor equipped with a magnetic stir bar, amixture of aromatic aldehyde (1.0 mmol), β-keto ester(2 mmol), ammonium acetate (1.5 mmol) and n-Fe3O4(at)ZrO2/HPW (0.003 g, 15 mol percent) was added. The reactorwas put in an oil bath with the temperature of 100 °C andthe reaction was carried out under solvent-free condition.The progress of the reaction was monitored using TLCplates. When the reaction was completed, the mixture wasallowed to cool to room temperature. Afterwards, the mixturewas triturated with 5mL ethyl acetate and the catalystwas separated by the help of an external magnet. Then thesolvent was evaporated and the crude product was recrystallizedfrom EtOH/H2O to offer the pure product.
90%
With uranyl nitrate hexahydrate; ammonium acetate In ethanol at 20℃; for 0.416667 h; Sonication
General procedure: To a solution of aldehyde (1.0 mmol), ethyl/methyl acetoacetate/acetylacetone (2.0 mmol) and ammonium acetate (1.0 mmol) in ethanol (3 mL), uranyl nitrate (10 molpercent) was added and the resultant reaction mixture was sonicated at room temperature for the required time (Table 1). The progress of the reaction was monitored by TLC. After completion of the reaction, the mixture was poured into crushed ice. The obtained solid was filtered, washed thoroughly with water, dried, and purified by recrystallisation in ethanol.
84%
at 55℃; for 3 h; Green chemistry
General procedure: A mixture of aldehyde (1 mmol), β-dicarbonyl compound (1or 2 mmol), NH4OAc (2.5 mmol), dimedone (1 mmol, whenused), and SBA-15/NHSO3H (5 molpercent) was stirred at 55 °C.After complete disappearance of starting material asindicated by TLC, the resulting mixture was diluted with hotEtOAc (10 mL) and filtered. The catalyst was completelyrecovered from the residue.
74%
With C21H38N(1+)*Mo11O40PV(4-)*3H(1+); ammonium acetate In ethanol at 78℃; for 8 h; Green chemistry
General procedure: The reaction was performed in a round bottom flask, whichwas equipped with a condenser and immersed in an oil bath. A mixture of methylacetoacetate (232 mg, 2 mmol), 2-nitrobenzaldehyde(151 mg, 1 mmol), ammonium acetate(100 mg, 1.3 mmol), and the selected catalyst (30 mg,1.5 percent mmol), in ethanol (8 mL) was thoroughly mixed andthen heated at 78 °C for 8 h. (to the end point of the reaction,checked by TLC). On cooling, the reaction mixture wasfiltered to separate the catalyst, the ethanol was evaporated,and the crude 1,4-dihydropyidine obtained was dried undervacuum (25 °C). The solid catalyst was washed with hexane(2 x 1 mL) and then, H2O (2 x 1 mL). The crude productwas recrystallized to give the pure 1,4-dihydropyridine.
Reference：
[1] RSC Advances, 2014, vol. 4, # 100, p. 56658 - 56664
[2] Tetrahedron Letters, 2010, vol. 51, # 8, p. 1187 - 1189
[3] Advanced Synthesis and Catalysis, 2012, vol. 354, # 10, p. 2001 - 2008
[4] Journal of Molecular Catalysis A: Chemical, 2014, vol. 382, p. 99 - 105
[5] Patent: CN107141249, 2017, A, . Location in patent: Paragraph 0114; 0115
[6] Synthetic Communications, 2016, vol. 46, # 24, p. 1989 - 1998
[7] RSC Advances, 2014, vol. 4, # 21, p. 10514 - 10518
[8] Journal of the Indian Chemical Society, 2009, vol. 86, # 9, p. 996 - 1000
[9] New Journal of Chemistry, 2018, vol. 42, # 15, p. 12539 - 12548
[10] Journal of Heterocyclic Chemistry, 2008, vol. 45, # 3, p. 737 - 739
[11] Catalysis Letters, 2017, vol. 147, # 6, p. 1551 - 1566
[12] Chemical Communications, 2011, vol. 47, # 32, p. 9230 - 9232
[13] Research on Chemical Intermediates, 2015, vol. 41, # 9, p. 6877 - 6883
[14] Journal of the Chinese Chemical Society, 2016, vol. 63, # 4, p. 336 - 344
[15] Synthesis, 2007, # 18, p. 2835 - 2838
[16] Organic Preparations and Procedures International, 2012, vol. 44, # 2, p. 153 - 158
[17] Synthetic Communications, 2004, vol. 34, # 23, p. 4349 - 4357
[18] Synthetic Communications, 2009, vol. 39, # 11, p. 1957 - 1965
[19] Chinese Journal of Chemistry, 2011, vol. 29, # 1, p. 118 - 122
[20] RSC Advances, 2014, vol. 4, # 37, p. 19111 - 19121
[21] Journal of Chemical Sciences, 2012, vol. 124, # 5, p. 1091 - 1096
[22] Medicinal Chemistry Research, 2013, vol. 22, # 1, p. 147 - 155
[23] Synlett, 2014, vol. 25, # 19, p. 2753 - 2756
[24] Canadian Journal of Chemistry, 2017, vol. 95, # 5, p. 530 - 536
[25] Asian Journal of Chemistry, 2012, vol. 24, # 12, p. 5649 - 5651,3
[26] Transition Metal Chemistry, 2010, vol. 35, # 1, p. 125 - 127
[27] Catalysis Letters, 2016, vol. 146, # 9, p. 1634 - 1647
[28] Chemical Communications, 2010, vol. 46, # 42, p. 8052 - 8054
[29] Journal of the Brazilian Chemical Society, 2011, vol. 22, # 3, p. 525 - 531
[30] Journal of Medicinal Chemistry, 1988, vol. 31, # 11, p. 2103 - 2107
[31] Organic Process Research and Development, 2001, vol. 5, # 4, p. 452 - 455
[32] Synthesis, 2006, # 8, p. 1283 - 1288
[33] Indian Journal of Chemistry, Section B: Organic Chemistry Including Medicinal Chemistry, 1995, vol. 34, # 10, p. 920 - 922
[34] Synthetic Communications, 2010, vol. 40, # 16, p. 2457 - 2463
5
[ 105025-71-6 ]
[ 104-88-1 ]
[ 73257-49-5 ]
Reference：
[1] Journal of Materials Chemistry A, 2013, vol. 1, # 37, p. 11210 - 11220
With iron oxide; ammonium acetate; at 80℃; for 0.3h;
General procedure: A mixture of the alkyl or aryl aldehyde (1 mmol), -dicarbonyl(2 mmol) and ammonium acetate (1.5 mmol) in the presence ofFe3O4NPs (0.024 g, equal to 10 mol%) was heated at 80C, withstirring. The progress of the reaction was monitored by TLC (elu-ent: EtOAc:n-hexane). After completion of the reaction, the mixturewas cooled to room temperature and then ethanol was added tothe resulting mixture and separated Fe3O4NPs by a normal mag-net. After evaporation of solvent, the solid product was filtered andrecrystallized from ethanol to give the pure products in 72-95%yields based on the starting aldehyde.
95%
With C23H3BF16N2O; ammonium acetate; In toluene; at 100℃; for 10.0h;
In a 100 mL single-necked flask, 0.01 mol% of Lewis acid-base bifunctional catalyst I was added (where Rf = CF3R1,R2, R3, R4, R5, R6 = F), 0.1 mol of p-chlorobenzaldehyde (R7 = 4-Cl-Ph), 0.1 mol of methyl acetoacetate (R8 = Me;Me), 0.1 mol of ammonium acetate, 10 mL of toluene, and the reaction was stirred at 100 C for 10 hours. TLC followed the reaction to complete the reaction. anti-The yield of the product II (R7 = 4-Cl-Ph; R8 = Me; R9 = Me) was 95%; the catalyst system was reused 10 timesAfter its catalytic performance did not decline
94%
With maltose; urea; mixture of; ammonium acetate; for 2.25h;Heating; Green chemistry;
General procedure: A mixture of aldehyde 1 (1 mmol), 1,3-dicarbonyl compound 2 (2 mmol), and nitrogen source 3 (3 mmol) were mixed and heated in the presence of a low-melting sugar mixture.The progress of the reaction was monitored by thin-layer chromatography (TLC) using n-hexane-ethyl acetate (7:3) as the solvent system. The Rf values of the product spots ranged from 0.5 to 0.6. After completion of the reaction, water was added to the reaction mixture to obtain the solid product as a precipitate. In cases where the product was obtained as a melt, several washings with water followed by bicarbonate solution gave crystalline products. The solids were filtered and washed with cold water. In most of the cases, the product obtained was pure, and when impure, the product was recrystallized from hot ethanol. Further two products were obtained as oils (Table 5, entries 4w and 4x). These products were extracted with ethyl acetate and dried over anhydrous Na2SO4. Evaporation of the solvent gave the pure product as an oil.
94%
With C34H20F13N2O6SZr(1+)*C6F13O3S(1-); ammonium acetate; In tetrahydrofuran; at 80℃; for 10.0h;
In a 50 mL round bottom flask, p-chlorobenzaldehyde (1 mmol), methyl acetoacetate (2.0 mmol), ammonium acetate (1.2 mmol), solvent THF (2 mL), and beta-naphthol Schiff base zirconium perfluorobutylsulfonate The acid complex (X = OSO 2 C 6 F 13 ) (0.05 mmol) was stirred at 80 C. for 10 h. After the reaction, the solvent was spin-dried, and the residue was extracted 3 times with CH 2 Cl 2. The solid catalyst was collected for recycling. The combined CH 2 Cl 2 filtrates were subjected to rotary evaporation. The residue was separated by silica gel column chromatography to obtain a pale yellow solid. 2,6-dimethyl-4- (p-chlorophenyl) -3,5-dimethoxycarbonyl-1,4-dihydropyridine, yield 94%.
91%
With ammonium acetate; at 100℃; for 0.25h;Green chemistry;
General procedure: To a glassy reactor equipped with a magnetic stir bar, amixture of aromatic aldehyde (1.0 mmol), beta-keto ester(2 mmol), ammonium acetate (1.5 mmol) and n-Fe3O4(at)ZrO2/HPW (0.003 g, 15 mol %) was added. The reactorwas put in an oil bath with the temperature of 100 C andthe reaction was carried out under solvent-free condition.The progress of the reaction was monitored using TLCplates. When the reaction was completed, the mixture wasallowed to cool to room temperature. Afterwards, the mixturewas triturated with 5mL ethyl acetate and the catalystwas separated by the help of an external magnet. Then thesolvent was evaporated and the crude product was recrystallizedfrom EtOH/H2O to offer the pure product.
90%
With uranyl nitrate hexahydrate; ammonium acetate; In ethanol; at 20℃; for 0.416667h;Sonication;
General procedure: To a solution of aldehyde (1.0 mmol), ethyl/methyl acetoacetate/acetylacetone (2.0 mmol) and ammonium acetate (1.0 mmol) in ethanol (3 mL), uranyl nitrate (10 mol%) was added and the resultant reaction mixture was sonicated at room temperature for the required time (Table 1). The progress of the reaction was monitored by TLC. After completion of the reaction, the mixture was poured into crushed ice. The obtained solid was filtered, washed thoroughly with water, dried, and purified by recrystallisation in ethanol.
87%
With ammonium acetate; In water; at 20℃; for 0.166667h;Sonication;
General procedure: Of each component, aldehyde 1 (1.0 mmol), ammonium acetate 2(1.0 mmol), and beta-keto ester 3 or dimedone 4 (2.0 mmol), in deionizedwater (2.0 mL) and in the presence of the fabricated Fe3O4/SiO2-PDANPs (50 mg) were ultrasonicated (50 KHz) for 10 min, at room temperature.After completion of the reaction, the NPs were magneticallyseparated, and the residual product was collected by filtration andwashed with ethanol and recrystallized to yield the pure product.
84%
With ammonium acetate; at 55℃; for 3.0h;Green chemistry;
General procedure: A mixture of aldehyde (1 mmol), beta-dicarbonyl compound (1or 2 mmol), NH4OAc (2.5 mmol), dimedone (1 mmol, whenused), and SBA-15/NHSO3H (5 mol%) was stirred at 55 C.After complete disappearance of starting material asindicated by TLC, the resulting mixture was diluted with hotEtOAc (10 mL) and filtered. The catalyst was completelyrecovered from the residue.
74%
With C21H38N(1+)*Mo11O40PV(4-)*3H(1+); ammonium acetate; In ethanol; at 78℃; for 8.0h;Green chemistry;Catalytic behavior;
General procedure: The reaction was performed in a round bottom flask, whichwas equipped with a condenser and immersed in an oil bath. A mixture of methylacetoacetate (232 mg, 2 mmol), 2-nitrobenzaldehyde(151 mg, 1 mmol), ammonium acetate(100 mg, 1.3 mmol), and the selected catalyst (30 mg,1.5 % mmol), in ethanol (8 mL) was thoroughly mixed andthen heated at 78 C for 8 h. (to the end point of the reaction,checked by TLC). On cooling, the reaction mixture wasfiltered to separate the catalyst, the ethanol was evaporated,and the crude 1,4-dihydropyidine obtained was dried undervacuum (25 C). The solid catalyst was washed with hexane(2 x 1 mL) and then, H2O (2 x 1 mL). The crude productwas recrystallized to give the pure 1,4-dihydropyridine.
With 2,2,6,6-Tetramethyl-1-piperidinyloxy free radical; iron(III) chloride hexahydrate; oxygen; sodium nitrite; In acetic acid; acetonitrile; at 20℃; for 0.5h;
General procedure: 1,4-DHPs (1 mmol, dissolved in 10 mL acetonitrile), TEMPO(0.05 mmol), FeCl3·6H2O (0.05 mmol), NaNO2 (0.05 mmol) and CH3COOH (1 mL) were added successively to a 25 mL three-neckedround-bottom flask equipped with a magnetic stirrer and a thermometer. The resulting mixture was stirred at room temperature and ambient pressure with an oxygen balloon until the reaction was completed as monitored by TLC (5:1 ethyl acetate/petroleum ether as eluent). Saturated aqueous NaHCO3 solution was added to make it neutral. The mixture was extracted with ethyl acetate three times. The combined organic extracts were washed with saturated aqueous NaCl solution, dried over MgSO4 and filtered. After removal of the solvent under reduced pressure, the residue was purified by columnchromatography (10:1 ethyl acetate/petroleum ether as eluent). Dimethyl 4-(4-chlorophenyl)-2,6-dimethyl-3,5-pyridinedicarboxylate(2l): Pale yellow solid, m.p. 138-140 C (lit.[24] 137-139 C). 1H NMR (500 MHz, CDCl3): delta 7.37 (d, J = 8 Hz, 2H), 7.19 (d, J = 8 Hz, 2H), 3.58 (s, 3H), 2.60 (s, 3H).
92%
With molybdenum(VI) tetrachloride oxide; In acetonitrile; for 0.166667h;Reflux;
General procedure: To a solution of corresponding 1,4-DHP (1.0 mmol) in CH3CN (10 mL), MoOCl4 (0.53 g, 2.1 mmol) was added and the reaction mixture was stirred for the time indicated in Table 2. After cooling to room temperature to the reaction mixture were added water (20 mL), dichloromethane (20 mL) and solid NaHCO3 (2 g) in a few portions. After stirring for 15 min. Organic extract was separated and water layer was additionally extracted with dichloromethane (2 × 10 mL). Combined organic extracts were dried over anhydrous Na2SO4, filtered and evaporated. The crude product was purified by column chromatography on silica gel (CH2Cl2/EtOAc, 9:1) to yield the product of purity >98%.
83%
With copper(ll) bromide; In chloroform; ethyl acetate; for 2.0h;Reflux;
General procedure: Equivalent amounts of 1,4-dihydropyridine (1, 3 mmol) and cupricbromide (3 mmol) were taken in a dry round-bottomed flask (25 mL) and ethylacetate-chloroform mixture (10 ml, v/v 1:1) was added to it. The flask wasfitted with a Liebig condenser fitted with a calcium chloride guard tube andwas refluxed for 1 h. The reaction was monitored by TLC after an interval of10 min. After completion, the reaction mixture was filtered through a flutedfilter paper, washed thoroughly with chloroform in order to remove theadhering cuprous bromide from the product and dried over anhydrous Na2SO4.Solvent was removed in vacuo and purified by column filtration to get pureproduct.
With ammonium acetate; In neat (no solvent); at 55℃; for 3.0h;Green chemistry;
General procedure: Polyhydroquinolines and DihydropyridinesA mixture of aldehyde (1 mmol), beta-dicarbonyl compound (1or 2 mmol), NH4OAc (2.5 mmol), dimedone (1 mmol, whenused), and SBA-15/NHSO3H (5 mol%) was stirred at 55 C.After complete disappearance of starting material asindicated by TLC, the resulting mixture was diluted with hotEtOAc (10 mL) and filtered. The catalyst was completelyrecovered from the residue
With iron supported on copper/Zeolite Socony Mobil-5 nanocatalyst; In water; at 20℃;Sonication;
General procedure: In a typical experiment, aromatic aldehyde (1 mmol), bketoester(2 mmol), ammonium acetate (1 mmol), and Fe-Cu/ZSM-5 (3 wt%) in 2 ml water were introduced in a 20-mL heavy-walled pear-shaped two-necked flask with nonstandard-tapered outer joint. The flask was attached to a12-mm tip diameter probe, and the reaction mixture was sonicated at ambient temperature at 20 % power of the processor. After completion of the reaction (monitored byTLC, within 5-8 min), the solid product was filtered,washed with water and ethanol, dried, and recrystallized from ethanol. The supported reagent was washed thrice with water and ethanol and dried under vacuum before reuse.
With ammonium hydroxide; In ethanol; at 110℃;Flow reactor;
General procedure: Diethyl 2,6-dimethyl-4-phenyl-1,4-dihydropyridine-3,5-dicarboxylate (4a). EtOH solution (3 mL) ofbenzaldehyde (0.67 M) mixed with ethyl acetoacetate (1.34 M) and the 25% aqueous NH3 (3 mL) wererespectively transferred into gas-tight syringe 1 and syringe 2. The syringes were placed in a LongerLSP02-1B syringe pump which was set to deliver the reactants into the mixer at identical flow rate of 6.7muL/min. The reaction mixture was then allowed to flow through a stainless steel tube reactor which wasdipped in a 110 C oil bath. The output mixture was collected in a cooled sample vial. After reactioncompletion, rinsed the reactor with ethanol to collect all of the reactant solution and then concentratedunder vacuum. The residue was subjected to silica gel column chromatography with Pet-EA (5:1) aseluent to give 4a (612mg, 93% yield).
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