(Official Hive Translator)
11-21-01 14:55
No 239082
      Syringaldehyde via Duff formylation
(Rated as: excellent)

Look what i found!

Interesting, but this obviously haven't been covered here, although exists in explicit form on OrgSyn,

Moreover - this is the 1st 'classic' Duff formylation (i.e., in glyceroboric acid) on this board - AFAIUTFSE, i've been looking for it for a long while.

I wonder if this can bee used on p-diMeObenzene, any comments, elder brothers? I know Duff is meant for phenols, but then I know for sure that p-diMeOB works fine in modified Duff - with TFA as solv't.

The yield of this rxn is low (~35%), but it is so OTC it makes SWIM wanna cry!

Here's the proc:

A well-stirred (Note 1) and (Note 2) mixture of 740 ml. of glycerol and 216 g. of boric acid, in a 2-l. three-necked round-bottomed flask fitted with a thermometer and a condenser for downward distillation, is dehydrated by heating in an oil bath to exactly 170. This temperature is maintained for 30 minutes and then allowed to drop. When the temperature has fallen to 150, a mixture of 154 g. (1 mole) of pyrogallol-1,3-dimethyl ether and 154 g. (1.1 moles) of hexamethylenetetramine (Note 3) is added as rapidly as possible through the neck holding the thermometer. The temperature drops to approximately 125. Rapid heating is immediately started but is slowed down when the temperature begins to reach 145 and stopped at 148. The reaction must be watched and controlled very carefully when this temperature is reached, since the reaction becomes exothermic at this point (Note 4), (Note 5), and (Note 6). The temperature is maintained at 150160 for approximately 6 minutes (Note 7). At the end of this reaction time the mixture is cooled to 110 as rapidly as possible (Note 6) and (Note 8), and a previously prepared solution of 184 ml. of concentrated sulfuric acid in 620 ml. of water is added to the reaction mixture. After being stirred for 1 hour, the mixture is cooled to 25 in an ice bath. The boric acid, which separates from the solution, is removed by filtration (Note 9) and washed free of mother liquor with 400 ml. of water. The filtrate and washings are combined and extracted with three 500-ml. portions of chloroform (Note 10), (Note 11), and (Note 12).
The chloroform solution is then extracted with a filtered solution of 180 g. of sodium bisulfite in 720 ml. of water (Note 13) by stirring rapidly with a Hershberg stirrer for 1 hour. The separated bisulfite solution is washed twice with chloroform, filtered, and acidified in a hood with a solution of 55 ml. of concentrated sulfuric acid in 55 ml. of water. After careful heating on a steam bath for a short time, air is bubbled through the hot solution until all the sulfur dioxide has been expelled. The product, which separates as a mixture of crystals and oil, readily solidifies upon cooling (Note 14). The syringic aldehyde is collected by filtration, washed with cold water, and dried in an oven at 40 to give 62.566 g. of light-tan material, melting at 110.5111, which still contains a small amount of foreign material that does not melt at 300. Recrystallization of the crude product from aqueous methanol using 30 ml. of water and 3 ml. of methanol for each 10 g. of aldehyde gives 5659 g. (3132%) of product melting clear at 111112 (uncor.). A second extraction of the chloroform solution with a filtered solution of 60 g. of sodium bisulfite in 240 ml. of water gives an additional 34 g. of product.

Please, comment.

(Hive Bee)
11-21-01 20:47
No 239160
      Re: Syringaldehyde via Duff formylation  Bookmark   

Very interesting procedure! Boric acid from borax, so easily OTC.... But, does this reaction go also with not-functionalized pyrogallol?
(Official Hive Translator)
11-21-01 21:32
No 239165
      Re: Syringaldehyde via Duff formylation  Bookmark   

I'd guess that pyrogallol will polymerize completely at this tempfrownfrown

The main question is - can one use this rxn for fully methylated phenols (like diMeObenzene) - beecause for phenols there already is Reimer-Tiemann, which is just as OTC and gives higher yields.

But, i'm pretty much sure that since rxn at the elevated temps proceeds very intensively, it would work as well on less activated rings. Actually, Duff formylations are often used precisely for electron-deficient compd's.

But that's only my guesses and i would really like someone more knowledgeable to comment on this proposal.

(Chief Bee)
11-22-01 10:44
No 239307
      Re: Syringaldehyde via Duff formylation  Bookmark   

This page talks about Duff formylation of 1,4-diethoxybenzene to 2,5-diethoxybenzaldehyde. References 13, 14 and 15 seems relevant to our purposes.

Duff found that heating phenols with HMTA in glycerol in the presence of glyceroboric acid, followed by an aqueous work up gave salicylaldehyde in rather low yields [13]. Suzuki employed modified conditions with a stronger acid, such as methanesulfonic, trifluoroacetic or polyphosphoric acid as a solvent [14], which successfully introduced the formyl group onto several electron-deficient aromatic rings [15].

2,5-Diethoxybenzaldehyde was previously synthesized in 85% yield by the formylation of 1,4-diethoxybenzene with SnCl4 and Cl2CHOCH3 (J. Am. Chem. Soc. 1979, 101, 2483).


A mixture of 1,4-diethoxybenzene (40 mmol) and HMTA (12.8 g, 92 mmol) in CF3COOH/CH3COOH  (30/90 mL) was heated to reflux for 3 h. After cooling, the mixture was poured into water and extracted with EtOAc. The combined extracts were washed with water, dried over Na2SO4. After removal of the solvent in vacuo, the residue was separated by column chromatography with hexane/EtOAc (6:1) as eluent to give 2,5-Diethoxybenzaldehyde, Yield, 34%; mp 61-62C (lit. mp 60-61C).

(Official Hive Translator)
11-22-01 18:24
No 239423
      Aqueous Duff formylation  Bookmark   

Thanks, Rhodium I was actually familiar w/this article, thats what I referred to when I said this formylation would work on p-dimethoxybenzene in TFA. Actually, it even goes further than that it states formylation of 1,3-diMeObenzene for 3 h in aqueous acetic acid, yielding ~35% (?) now as I understand it, meta-diMeObenzene should bee much easier formylated since both of it MeO- groups  point at the same direction but could it bee that the rxn w/para-diMeOB is just slower?

To find that out, SWIMs set up this rxn (36 ml AcOH, 7 ml aqua, 5 g HMTA, 2 g DMB) for 48 hours at reflux well, he wants to tell you that during the 1st 24 h the colour hasnt changed appreciably its probably more bad that good, SWIMd guess. Hell let you know of the outcome.

Another important, although unrelated, question Rhodium, did you ever get my PMs??? If you did Im asking you again for ANY reply. If you would, please.


(Chief Bee)
11-22-01 19:16
No 239439
      Re: Aqueous Duff formylation  Bookmark   

I got your PM's, I'm just lagging behind with answering 40-50 PM's as usual. Unfortunately I must say that the answer to your main question is negative frown
(Master Searcher)
11-22-01 19:46
No 239444
      Re: Aqueous Duff formylation  Bookmark   

So, Rhodium.  Do you get any RP questions like I do?  Maybe they don't want to post their question and open themselves up to flaming.
(Chief Bee)
11-22-01 21:10
No 239461
      Re: Aqueous Duff formylation  Bookmark   

Yes, I get those, but they are directly answered with a simple "Ask in the meth forum". The ones lagging behind are those that require some thought/research/evaluation for me to answer, and that takes time to do, which I haven't got too much of. But this is off topic, let's return to the Duff formylation.
(Official Hive Translator)
11-25-01 19:35
No 240359
      Re: Aqueous Duff formylation  Bookmark   

Well bees it is evidently impossible to formylate p-DMB in aq. AcOHfrowncrazytonguetongue

Perhaps we should make a new forum named "Failed synthetic attempts" - specially for SWIMlaugh

Any more thoughts on 'glyceric' Duff?

(Distinctive Doe)
09-11-02 16:55
No 355308
      More Duff Reaction
(Rated as: excellent)

The Duff reaction for the preparation of o-hydroxyaldehydes.
Liggett, Lawrence M.; Diehl, Harvey.   
Iowa State Coll.,  Ames,    Proc. Iowa Acad. Sci.  (1945),  52  191-7. 
CAN 41:714  AN 1947:714
The method of Duff for the synthesis of o-HO aldehydes has been applied to a sufficiently large no. of phenols to warrant the conclusion that it is as general a reaction as the Reimer-Tiemann reaction.  The Duff method is shorter and gives better yields.  It has been successfully applied to several phenols on which the Reimer-Tiemann method fails.  It is not applicable to the prepn. of aldehydes from nitrophenol, dinitrophenol, thiophenol, or 2-hydroxypyridine. 

Improved general procedure: A mixt. of 300 g. glycerol and 70 g. boric acid was heated in a 2-l. beaker with stirring until the temp. reached 165.  About 20 min. was usually required for the operation since a considerable amt. of water had to be expelled.  An intimate mixt. of 50 g. of the phenol and 50 g. hexamethylenetetramine was prepd. by grinding the materials together thoroughly.  The mixt. was then added with vigorous stirring to the glycerol-glyceroboric acid soln. previously cooled to 150.  The reactants were stirred for 20 min., during which the temp. was maintained between 150 and 165 by heating or cooling as necessary.  Finally the reaction mixt. was allowed to cool to 115 and was then acidified with a mixt. of 50 ml. concd. H2SO4 and 150 ml. water.  When larger quantities of phenol were employed the quantities of the other reactants were increased in proportion.  The method most frequently employed for the isolation of the o-HO aldehyde from the above reaction mixt. consisted in steam-distg. the acidified reaction mixt.  The removal of the aldehyde by this method was hastened by the fact that the viscous reaction mixt. could be heated to about 110-20 while steam was being passed through it.  This was a distinct advantage in the case of difficultly volatile aldehydes.  The aldehydes, when liquid, were usually insol. and easily sepd. from the distillate.  In some cases extn. with ether or benzene was necessary.  When solid, the aldehydes were filtered off after cooling the steam distillate in an ice bath. In the case of aldehydes which could not be distd. with steam, the cold, acidified reaction mixt. was extd. directly with ether or benzene. 

New compds. obtained were: 2-Hydroxy-3,5-dibromobenzaldehyde (from 2,4-dibromophenol), yield 6.8%, m. 75-7 (from alc.); phenylhydrazone, m. 141-2; Schiff base with (CH2NH2)2 (I), (from PrOH), m. 247.  2-Hydroxy-5-methylbenzaldehyde (from p-cresol), yield 29%, m. 55.8; Schiff base with I, m. 164.  2-Hydroxy-3-butoxybenzaldehyde (from 2-butoxyphenol, b. 150-4), yield 15%, m. 49; Schiff base with I, m. 93.5.  2-Hydroxy-3-isopropyl-5-chloro-6-methylbenzaldehyde (from p-chlorothymol), yield 10%, m. (from alc.) 49; oxime, m. 150-1; Schiff base with I, m. 171.  Aldehyde from 2-hydroxy-4-tert-butylphenol, yield 26%, yellow crystals from alc. m. 85; phenylhydrazone, m. 160-1; Schiff base with I, m. 226.  2-Hydroxy-3-chloro-5-tert-butylbenzaldehyde (from 2-chloro-4-tert-butylphenol), yield 29%, pale yellow crystals from alc., m. 72; phenylhydrazone, m. 146; Schiff base with I (from alc.), m. 115.  2-Hydroxy-3-tert-amylbenzaldehyde (from 2-tert-amylphenol, b45 147-8), yield 11%, b10 106 (after careful distn.); Schiff base with I, m. 109.5.  2-Hydroxy-3-methyl-5-tert-amylbenzaldehyde, light yellow oil, b1 108-10 (from 2-methyl-4-tert-amylphenol, b39 158-9), yield 19%; Schiff base with I, m. 90 (from alc.).  Fourteen references.

Read and Listen!!!
(Distinctive Doe)
09-11-02 17:00
No 355310
(Rated as: excellent)

Hydroquinonic aldehydes. II.
Cardani, Cesare; Grunanger, Paolo.   
Gazz. chim. ital.  (1955),  85  252-62. 
CAN 50:56769    AN 1956:56769  

cf. C.A. 49, 2357b.  In a continued study of disubstituted hydroquinonic aldehydes, the conditions of oxidation were changed so that better yields were obtained.  The possibility of applying the Duff reaction directly to hydroquinones instead of to phenols was then studied.  p-C6H4(OH)2 (I) does not react in this way, but 1,4,2,5-(HO)2C6H2Me2 (II) and 5,4,2-Me(HO)2C6H2CHMe2 (III) from the corresponding aldehydes.  The secondary products isolated from the Duff reaction are phenols, and in the Elbs oxidation of salicylaldehydes are dialdehydes and hydroquinones. 

Aq. K2S2O8 (21.3 g. in 800 cc.), added during 4 hrs. (50 cc. each 15 min.) to a mixt. of 9.2 g. KOH in 274 cc. H2O and 100 cc. C5H5N and 8 g. carvacrylaldehyde at 16-18, the mixt. let stand 18 hrs., acidified (Congo red), filtered, extd. with Et2O, 1/6 vol. of concd. HCl added to the aq. soln., the soln. heated at 70, let stand, filtered, the residue (1.1 g.) extd. with hot petr. ether, the ext. let stand, the ppt. sublimed in vacuo, the residue from the hot extn. sublimed, and the 2 products combined, gives 0.6 g. 3,6,2,5-Me(Me2CH)(HO)2C6HCHO (IV), m. 184.5-5.  The aq. soln. extd. with Et2O, the ext. dried by Na2SO4, evapd., and the residue extd. with warm H2O, leaves a little IV.  C5H5N was used to increase the soly. of the intermediate alk. salt and thus increase the yield.  Glycerol (32 cc.) and 9 g. H3BO3 heated 30 min. at 170, a mixt. of 6.4 g. II and 6.4 g. (CH2)4N6 (V) added slowly (keeping the temp. not over 160), the mixt. cooled to 110, 7.7 cc. concd. H2SO4 in 26 cc. H2O added, the mixt. extd. with Et2O, the ext. evapd., and the residue purified by C6H6, give 0.8 g. 2,5,3,6-Me2(HO)2C6HCHO (VI), m. 139-41.  Alc. VI (0.2 g. in 10 cc.) and 0.15 g. o-C6H4(NH2)2 refluxed 4 hrs., let stand, and the ppt. purified by EtOH, give the Schiff base, C15H16O2N2, orange-yellow, m. 210.  III (3.5 g.) and 3.5 g. V made to react in the same way with 4.9 g. H3BO3 and 17 g. glycerol, the mixt. acidified with dil. H2SO4, the ppt.
(9.2 g.) dissolved in Et2O, the soln. percolated through a column of active Al2O3, and the 1st fraction evapd., give 1.2 g. 2,5,3,6-Me(Me2CH)(HO)2C6HCHO m. 180-1.  Elution with Et2O, and then Et2O-MeOH, gives a product with lower m.p., probably a mixt. of 2 isomeric aldehydes, which could not be sepd. even by repeated sublimation or crystn. from C6H6.  o-Allylphenol (8 g.) and 8 g. V, added slowly to 40 cc. glycerol and 11.2 g. H3BO3 at 150-60, the mixt. heated 15 min. longer at 150-60 and cooled to 110 9.6 cc. concd. H2SO4 + 32 cc. H2O added slowly, the mixt. steam distd., the distd. oil extd. with Et2O, and the ext. dried and evapd., give 1.05 g. 2.3-HO(CH2:CHCH2)C6H3CHO (VII), yellowish oil, b2 90.  Further steam distn. gives a small amt. of an impure compd. (VIII), m. 71-3. 

Following the procedure of Renz (C.A. 41, 4128h), oxidation of VII by alk. K2S2O8, decompn. of the ester by heating with an acid, cooling, and purification of the ppt. by H2O, gives 3,2,5-CH2: CHCH2(HO)2C6H2CHO (IX), yellow, m. 120-1.  IX (0.2 g.) in glacial AcOH and 0.4 g. PhHNHNH2 let stand 2 hrs., poured into ice-water, and the ppt. purified by C6H6, give the phenylhydrazone, C10H16O2N2, m. 116-17; in EtOH with FeCl3 it gives intense violet solns., which are decolorized by reducing agents.  In dil. aq. alkalies, IX slowly oxidizes to a violet product.  IX (0.1 g.) and 0.15 g. 2,4-(O2N)2C6H4NHNH2 in MeOH contg. a little HCl, heated briefly, and the product purified by EtOH, give the dinitrophenylhydrazone, C16H14O6N4, red, m. 258-9 (decompn.).  The white product obtained in the prepn. of 3,6,2-Me2(HO)C6H2CHO from the steam distillate (cf. C.A. 49, 2357b), purified by MeOH, gives 2,5,4,6-Me2(OHC)2C6HOH, m. 159; phenylhydrazone, yellow, m. 209-10 (decompn.).  VIII, purified by hexane, gives 2,4,6-CH2:CHCH2(OHC)2C6H2OH (X), m. 75-6.  With excess alc. PhHNNH2, X gives, after purification by glacial AcOH, the bis(phenylhydrazone), C23H22ON, yellow, m. 208-10 (decompn.).

With p-O2NC6H4NHNH2 in glacial AcOH, X gives, after purification by aq. C5H5N, the bis(p-nitrophenylhydrazone), C23H20O5N6, intense red, decomp. 275-80.  Prolonging the steam distn. or extg. with Et2O the nonvolatile residue in the prepn. of 2,5,6-Me(Me2CH)(HO)C6H2CHO, and crystg. the product from EtOH, gives 5,2,4,6-Me(Me2CH)(OHC)2C6HOH, m. 79.  With excess alc. PhNHNH2, and purification by glacial AcOH, it gives the bis(phenylhydrazone), C24H26ON4, yellow, m. 197-8 (decompn.). 

The prepn. of 2,5,3,6-Me(Me2CH)(HO)2C6HCHO (XI) already described (cf. loc. cit.) was modified.  After having acidified with concd. HCl and heated the soln. at 70, the ppt. was sepd. to obtain XI.  The aq. mother liquor, extd. with Et2O, the ext. evapd., the residue fractionally crystd. from boiling water to remove XI, the mother liquor satd. with (NH4)2SO4 or extd. with Et2O, and the recovered product purified by sublimation, gives thymohydroquinone (XII), m. 143.  The yield is 0.2 g. per 8 g. thymolaldehyde.  The ppt. formed by satg. with (NH4)2SO4 the mother liquor in the prepn. of IV, sublimed and crystd. from H2O, gives XII.  In the prepn. of IX, the filtrate from the removal of IX, extd. with Et2O, and the ext. evapd., gives a mixt. of IX and another compd.; the latter, sepd. by H2O (IX is insol.), the soln. satd. with (NH4)2SO4, extd. with Et2O, the ext. evapd., and the residue purified by C6H6, gives allylhydroquinone, m. 93. 

Applied to I, the Duff reaction does not give an appreciable yield of 2,5-(HO)2C6H4CHO, but some unaltered I and a large amt. of resin. 

Read and Listen!!!
03-07-03 23:56
No 414682
      ref claims better yields  Bookmark   

From the wanted refs sticky thread in Novel discourse :

much improved Duff ref.   Bookmark  Reply    

Does someone has access to the journal "Chemistry Express"?
I believe it's Japanese but written in English

CAN 114:184910 describes the improved Duff reaction with ArOH, Ac2O and hexamine ---> HOArCHO, yields exceeding 70% !

 it's CHEM. EXPRESS (1991), 6(1), p37-40
04-10-03 16:36
No 425391
      Another Duff Formylation in aqueous AcOH
(Rated as: excellent)

Organic Synthesis. vol 75, 1. Jay F Larrow, Eric N Jacobsen, 1998

3,5-di-tert-butylsalicylaldehyde (2-hydroxy-3,5-di-tert-butyl-benzaldehyde) is synthesised from 2,4-di-tert-butylphenol.

3,5-Di-tert-butylsalicylaldehyde (Note 9). A 2-L, three-necked, round-bottomed flask equipped with a mechanical overhead stirrer, reflux condenser, and thermometer is charged with 125 g (0.60 mol) of 2,4-di-tert-butylphenol, 170 g (1.20 mol, 2 eq) of hexamethylenetetramine, and 300 mL of glacial acetic acid (Note 10). Complete dissolution results within minutes after stirring is initiated. The reaction mixture is heated to 130C over a period of 60 min or less, and the temperature is diligently maintained within a range of 125-135C for 2 hr as stirring is continued (Note 11). The reaction mixture is then cooled to 75-80C and aqueous sulfuric acid [300 mL of 33% (w/w)] is added with stirring while the temperature is maintained below 100C (Note 12). After the resulting mixture is heated to reflux (105-110C) for 30-60 min, the reaction mixture is cooled to 75-80C and transferred to a 1-L separatory funnel wrapped with electrical heating tape (Note 13). The phases are allowed to separate while the temperature is maintained at 75-80C; the lower aqueous phase (650 to 750 mL; pH 4-5) is drawn off (Note 14). The organic layer is transferred to an Erlenmeyer flask and cooled to 50C, at which point methanol (100 mL) is added with stirring. The mixture is cooled to room temperature, then to <=5C with an ice bath and maintained at that temperature for 1 hr with continued stirring. The product is collected by vacuum filtration and the solid is washed with 30 mL of cold (<=5C) methanol. Air is pulled through the filter cake for not less than 30 min to remove most of the solvent (Note 15). The crude product is suspended in methanol (approximately 1:1; w/v) and the mixture is heated to 50-55C for 30 min with stirring (Note 16). The solution is cooled to <=5C over a 1-hr period and this temperature is maintained for another hour. The product is collected by vacuum filtration and washed with 20 mL of cold methanol. The product is allowed to air dry and is isolated as a free-flowing yellow solid, mp >=52C (Note 17) and (Note 18).
9. This procedure is an adaptation of the Duff reaction.
10. The order of addition does not seem to be important. If the sequence that is described is employed, a slight exotherm is observed upon addition of the acetic acid.
11. Extreme care should be taken to maintain the reaction mixture temperature within the stated limits. Heating too slowly results in increased formation of side products and decreased product yield, as does allowing the reaction temperature to increase above 135C. A mild exotherm is exhibited once the reaction reaches about 110C, and the upper temperature limit can be exceeded if the rate of heating is not carefully monitored.
12. Addition of the sulfuric acid solution is exothermic and can cause vigorous evolution of steam. The acid solution should be cooled to (or below) room temperature before addition.
13. The checkers used a 1-L resin kettle (Kontes #614010-1000) with a temperature controller and preheated at 80C.
14. It is important that sufficient time be allowed for proper partitioning between the phases. The heating tape maintains the temperature in the desired range, preventing the precipitation of solids and allowing for better separation. The phases should be allowed to separate for at least 15 min. If a small amount of solids is observed, this should not interfere with the separation and the solids may be discarded with the aqueous phase.
15. The typical yield for the crude aldehyde is 71-85 g (50-60%).
16. Any solids remaining in the mixture after 30 min at 50-55C should be removed by filtration. The amount of solid is typically less than 1 g.
17. The typical yield of the recrystallized product is 50.0-64.3 g (35-45%). The literature melting point of the product is 58-60C, but high purity samples (>=98% by GC) generally have melting points in the given range.
18. The spectral properties of the product are as follows: 1H NMR (300 MHz, CDCl3) : 1.33 (s, 9 H), 1.43 (s, 9 H), 7.35 (d, 1 H, J = 2.4), 7.59 (d, 1 H, J = 2.4), 9.87 (s, 1 H), 11.65 (s, 1 H); 13C NMR (75 MHz, CDCl3) : 29.4, 31.4, 34.3, 35.1, 120.2, 127.8, 131.9, 137.8, 141.7, 159.2, 197.2; IR (KBr) cm−1: 1653, 1612, 1373, 1322, 1265, 1170.

It's the reaction at the bottom of this page:

Full details available on

This is a similar procedure to a synthesis posted previously for 3,5-di-tert-butyl-4-hydroxybenzaldehyde. Lower yield though.
Post 208298 (Antoncho: "Duff formylation in aq. AcOH - 90% yield :))", Chemistry Discourse)

Who do you believe, me or your own eyes?
04-10-03 16:51
No 425396
      Duff Formylation of non-phenolic arenes  Bookmark   

from a review article "Hexamethylenetetramine, a versatile reagent in organic synthesis"
Blazevic, Kolbah, Belin, Sunjic, & Kajfez
(ref missing)

  A modification of this reaction uses trifluoroacetic acid as solvent and a variety of aromatic compounds, including simple hydrocarbons, can thus be converted into aldehydes. Reaction conditions are milder and yields are higher than in the Duff procedure. A high para-regioselectivity is observed when the formylation is conducted under these conditions.
  See Smith WE, J.Org.Chem. (1972) 37:3972.

Who do you believe, me or your own eyes?