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All 3 posts Subject: 3,4,5-TMB from p-Cresol Please login to post Down

slothrop
(Newbee)
08-13-02 14:12
No 345054
      3,4,5-TMB from p-Cresol
(Rated as: excellent)

Efficient and Convenient Synthesis of 3,4,5-Trimethoxybenzaldehyde From p-Cresol
Ya-Fei Ji, Zhi-Min Zong, Xian-Yong Wei
Synthetic Communications Vol.32, No.18, pp. 2809–2814 (2002) (https://www.rhodium.ws/chemistry/345tmb.p-cresol.html)

Abstract
With p-cresol as starting material, 3,4,5-trimethoxybenzaldehyde was synthesized in an overall yield of 67.4% via bromination, hydrolysis, methoxylation and methylation.

3,5-Dibromo-4-hydroxybenzaldehyde

3-Necked round-bottomed ﬂask equipped with a condenser attached to a calcium chloride drying tower,a mechanical stirrer,a thermometer,and a dropping funnel was charged with a solution of 43.2 g (0.40 mol)of p-cresol in 200 mL of o-dichlorobenzene. The solution was cooled to 10 C and treated during 1 h with a solution of 130.0 g (0.81 mol) of bromine in 100 mL of o-dichloro-benzene at such a state that the temperature was kept below 40 C. The mixture was stirred, heated at 160°C and simultaneously dropped with another solution of 130.0 g (0.81 mol) of bromine in 100 mL of o-dichloro-benzene during 3 h. This deep red mixture was sequentially stirred for 30 min. After being cooled to room temperature and 145 mL of water being added,the mixture was heated to 120°C and kept at the temperature for 4 h. After being cooled to 5°C, the mixture was separated into upper organic layer, middle aqueous layer and lower solid layer. The solid product was collected by ﬁltration and washed with water up to neutrality. It was dried in vacuo at 50°C to give 91.4 g (81.6%)of the off-white solid m.p.180–182°C (lit.179 –182 C).

3,4,5-Trimethoxybenzaldehyde

About 142.0 g (0.74–0.79 mol) of freshly prepared 28–30 wt %sodium methoxide, 8 mL of DMF, 4 g of cuprous chloride and 56.0 g (0.20 mol) of 3,4-Dibromo-4-hydroxybenzaldehyde were added into a 500 mL magnetically stirred stainless steel autoclave. After the air was replaced with N2, the autoclave was heated to 120°C and kept at the temperature for 3 h. After being cooled to room temperature, the reaction mixture was taken out from the autoclave and transferred into a round-bottomed ﬂask. Solvents were evaporated from the ﬂask in vacuo below 60°C, and the residue was treated with 200 mL of water. The mixture was stirred and heated to 90°C for dissolution, then cooled to 0°C for crystallization. After NaBr dissolved in the stock was removed by filtration, yellow green sodium phenolate 8 was obtained. The ﬁlter cake was dissolved in 300 mL of water, added with 1.5 g of active carbon,and then heated to 95°C for 30 min. After hot-ﬁltration for removing the filter residue (catalyst included), the filtrated stock was cooled to 40°C, and was treated by slowly dropping 50.0 g (0.40 mol) of dimethylsulfate and 30 wt% 112 g (0.84 mol) of NaOH aqueous solution during 2 h. The pH value should be carefully controlled within 8.5–9.3. Stirring was continued at 50°C for 30 min and then at 0°C for 30 min, and the product was collected by filtration. It was washed with water up to neutrality and dried in vacuo at 45°C to give 32.4 g (82.6%) of 3,4,5-trimethoxybenzaldehyde as colorless crystals, m.p. 74–75°C (lit. 73–75°C).

Rhodium
(Chief Bee)
10-04-03 20:21
No 462610
User Picture       3,5-Dibromo-4-hydroxybenzaldehyde

Similar to the above procedure...

3,5-Dibromo-4-hydroxybenzaldehyde
Indian Journal of Chemistry 32B, 872-873 (1993)

Bromine (122.7g, 766 mmol) was added gradually at 25°C in 1 hr to p-cresol (19.6 g, 181 mmol) in 60 ml anhydrous chlorobenzene. The temperature of the reactants was raised and the mixture stirred under reflux for 4 hr. Chlorobenzene was distilled in vacuo and the residue poured in cold methanol (200 ml) containing 1N HCl (100 ml). The precipitate was filtered, washed with water, dried and crystallized from dichloromethane-hexane furnishing fine crystals of the title product in 55% yield, mp 179-181°C (lit. mp 180-82°C).

Rhodium
(Chief Bee)
06-21-04 12:22
No 514596
User Picture       Many routes to 3,4,5-Trimethoxybenzaldehyde
(Rated as: excellent)

Synthesis of 3,4,5-Trimethoxybenzaldehyde
P.S. Manchand, P.S. Belica, and H.S. Wong
Synth. Commun. 20(17), 2659-2666 (1990) (https://www.rhodium.ws/chemistry/345-tmba.html)

Abstract
The copper(I)-catalyzed exchange of bromine by methoxide in 5-bromovanillin and in 3,5-dibromo-4-hydroxybenzaldehyde provides an efficient method for preparing 3,5-dimethoxy-4-hydroxybenzaldehyde, from which 3,4,5-trimethoxybenzaldehyde is obtained by methylation with dimethylsulfate.

An Efficient Synthesis of 3,4,5-Trimethoxybenzaldehyde from Vanillin
D.V. Rao & F.A. Stuber
Synthesis 308 (1983) (https://www.rhodium.ws/chemistry/345-tmba.vanillin.html)

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	All 3 posts		Subject: 3,4,5-TMB from p-Cresol		Please login to post		Down


		slothrop (Newbee) 08-13-02 14:12 No 345054				3,4,5-TMB from p-Cresol (Rated as: excellent)
						Efficient and Convenient Synthesis of 3,4,5-Trimethoxybenzaldehyde From p-Cresol Ya-Fei Ji, Zhi-Min Zong, Xian-Yong Wei Synthetic Communications Vol.32, No.18, pp. 2809–2814 (2002) (https://www.rhodium.ws/chemistry/345tmb.p-cresol.html) Abstract With p-cresol as starting material, 3,4,5-trimethoxybenzaldehyde was synthesized in an overall yield of 67.4% via bromination, hydrolysis, methoxylation and methylation. 3,5-Dibromo-4-hydroxybenzaldehyde 3-Necked round-bottomed ﬂask equipped with a condenser attached to a calcium chloride drying tower,a mechanical stirrer,a thermometer,and a dropping funnel was charged with a solution of 43.2 g (0.40 mol)of p-cresol in 200 mL of o-dichlorobenzene. The solution was cooled to 10 C and treated during 1 h with a solution of 130.0 g (0.81 mol) of bromine in 100 mL of o-dichloro-benzene at such a state that the temperature was kept below 40 C. The mixture was stirred, heated at 160°C and simultaneously dropped with another solution of 130.0 g (0.81 mol) of bromine in 100 mL of o-dichloro-benzene during 3 h. This deep red mixture was sequentially stirred for 30 min. After being cooled to room temperature and 145 mL of water being added,the mixture was heated to 120°C and kept at the temperature for 4 h. After being cooled to 5°C, the mixture was separated into upper organic layer, middle aqueous layer and lower solid layer. The solid product was collected by ﬁltration and washed with water up to neutrality. It was dried in vacuo at 50°C to give 91.4 g (81.6%)of the off-white solid m.p.180–182°C (lit.179 –182 C). 3,4,5-Trimethoxybenzaldehyde About 142.0 g (0.74–0.79 mol) of freshly prepared 28–30 wt %sodium methoxide, 8 mL of DMF, 4 g of cuprous chloride and 56.0 g (0.20 mol) of 3,4-Dibromo-4-hydroxybenzaldehyde were added into a 500 mL magnetically stirred stainless steel autoclave. After the air was replaced with N2, the autoclave was heated to 120°C and kept at the temperature for 3 h. After being cooled to room temperature, the reaction mixture was taken out from the autoclave and transferred into a round-bottomed ﬂask. Solvents were evaporated from the ﬂask in vacuo below 60°C, and the residue was treated with 200 mL of water. The mixture was stirred and heated to 90°C for dissolution, then cooled to 0°C for crystallization. After NaBr dissolved in the stock was removed by filtration, yellow green sodium phenolate 8 was obtained. The ﬁlter cake was dissolved in 300 mL of water, added with 1.5 g of active carbon,and then heated to 95°C for 30 min. After hot-ﬁltration for removing the filter residue (catalyst included), the filtrated stock was cooled to 40°C, and was treated by slowly dropping 50.0 g (0.40 mol) of dimethylsulfate and 30 wt% 112 g (0.84 mol) of NaOH aqueous solution during 2 h. The pH value should be carefully controlled within 8.5–9.3. Stirring was continued at 50°C for 30 min and then at 0°C for 30 min, and the product was collected by filtration. It was washed with water up to neutrality and dried in vacuo at 45°C to give 32.4 g (82.6%) of 3,4,5-trimethoxybenzaldehyde as colorless crystals, m.p. 74–75°C (lit. 73–75°C).



		Rhodium (Chief Bee) 10-04-03 20:21 No 462610				3,5-Dibromo-4-hydroxybenzaldehyde
						Similar to the above procedure... 3,5-Dibromo-4-hydroxybenzaldehyde Indian Journal of Chemistry 32B, 872-873 (1993) Bromine (122.7g, 766 mmol) was added gradually at 25°C in 1 hr to p-cresol (19.6 g, 181 mmol) in 60 ml anhydrous chlorobenzene. The temperature of the reactants was raised and the mixture stirred under reflux for 4 hr. Chlorobenzene was distilled in vacuo and the residue poured in cold methanol (200 ml) containing 1N HCl (100 ml). The precipitate was filtered, washed with water, dried and crystallized from dichloromethane-hexane furnishing fine crystals of the title product in 55% yield, mp 179-181°C (lit. mp 180-82°C).



		Rhodium (Chief Bee) 06-21-04 12:22 No 514596				Many routes to 3,4,5-Trimethoxybenzaldehyde (Rated as: excellent)
						Synthesis of 3,4,5-Trimethoxybenzaldehyde P.S. Manchand, P.S. Belica, and H.S. Wong Synth. Commun. 20(17), 2659-2666 (1990) (https://www.rhodium.ws/chemistry/345-tmba.html) Abstract The copper(I)-catalyzed exchange of bromine by methoxide in 5-bromovanillin and in 3,5-dibromo-4-hydroxybenzaldehyde provides an efficient method for preparing 3,5-dimethoxy-4-hydroxybenzaldehyde, from which 3,4,5-trimethoxybenzaldehyde is obtained by methylation with dimethylsulfate. An Efficient Synthesis of 3,4,5-Trimethoxybenzaldehyde from Vanillin D.V. Rao & F.A. Stuber Synthesis 308 (1983) (https://www.rhodium.ws/chemistry/345-tmba.vanillin.html) ^{The Hive - Clandestine Chemists Without Borders}

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