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All 3 posts Subject: Proposed route to P2P or 4-Me-P2P from citral Please login to post Down

Vitus_Verdegast
(Hive Addict)
03-01-04 00:39
No 491925
User Picture       Proposed route to P2P or 4-Me-P2P from citral

Citral is everywhere, it is present in good amounts in lemon grass oil, orange peel oil and other citrus fruits. Citral is abundantly used in the food, cosmetics and perfumery industry, it's even more cheap than Iraqi oil and practically unwatchable.

Citral consists of a cis- isomer (citral-a or geranial) and a trans- isomer (citral-b or neral).

First, we'll have a look at Tetrahedron (1970) vol 26 p. 4901-4913 (DOI:10.1016/S0040-4020(01)93142-4):

Abstract
The acid catalysed cyclization of citral gives p-cymene and p-alpha-dimethylstyrene. The ratio of the arenes is dependent both upon the pH of the reaction medium and upon the presence or complete absence of oxygen. At pH 1·8 in the presence of oxygen the yield of the styrene is at a maximum to the almost complete exclusion of p-cymene.

I will give the experimental details here, if someone with access to the full-text PDF could post it here, it would be much appreciated.

Since Semmler's original observations in 1891 of the cyclization of citral in the presence of KHSO₄, the reaction has been studied by many workers using a variety of acidic catalysts and reaction temperatures. Under all conditions a single stable end-product has been isolated and shown to be p-cymene. Now these authors found that a change in the pH of the reaction medium alters the rate of initial cyclization step but it also results indirectly in the formation of end products other than p-cymene. Under an atmosphere of oxygen at pH 1.8 the predominant stable end product of the cyclization of citral is p-alpha-dimethylstyrene.

When citral in a solution at pH 1.8 was stirred for 22 hours in an atmosphere of nitrogen, there was obtained a mixture of:
p-cymene : 81%
p-alpha-dimethylstyrene: 16.6%
alpha-menthadiene (?) : 0.7%
alpha-phellandrene : 0.7%
and 2 unknown componds, each one in 0.5% yield

After 6 hours of stirring at pH 0.5 under nitrogen there was already obtained 79% p-cymene and only 10% p-alpha-dimethylstyrene.

When citral in a solution at pH 1.8 was stirred for 22 hours in an atmosphere of oxygen, there was obtained a mixture of:
p-alpha-dimethylstyrene : 79%
p-cymene : 7.7%
alpha-menthadiene (?) : 3.9%
and three unknown compounds at 2.4, 2.2 and 1.9% yield.

After 6 hours of stirring at pH 1.75 under oxygen there was obtained 69% p-alpha-dimethylstyrene and 3.8% p-cymene. Lower pH values gave lower yield of p-alpha-dimethylstyrene (19.8% at pH 0.4) but high yields of p-cymene instead (71.5% at pH 0.4).
pH Values of 2.0 and greater gave chiefly piperitenol under nitrogen and unreacted citral under oxygen.

Acid catalysed rearrangements
Citral (0.94g, 1 mL) in an aqueous solution (10 mL) of known pH was vigorously stirred at 70° for a known period of time. The atmosphere above the reaction mixture was controlled by passing the gas (either "white spot" nitrogen, scrubbed by passage through Cr(II) solution, or O₂) through the reaction mixture at a constant rate. A mercury bubbler seal ensured a slight positive pressure of the gas in the reaction flask at all times. The reaction was quenched by rapidly cooling the mixture to 0° and the products and unreacted citral were extracted immediately with light petroleum (commercial light petroleum, bp. 30-40° (May and Baker) was fractionally distilled from P₂O₅ to give a fraction having a single GLC peak on the LAC 2R-446 column), 15 mL + 2x 5 mL. The combined extracts were made up to 25 mL and n-octanal (8 microliter) was added to a sample of the extracts (2 mL) and the composition of the sample analysed with a Perkin-Elmer F11 gas chromatograph.

p-cymene from citral and KHSO₄ : F.W. Semmler, Ber. Deutsch. Chem. Gesell. 24, 202 (1891)
Free full-text PDF can be found at : http://gallica.bnf.fr/PeriosListe.htm

A practical route to p-alpha-dimethylstyrene can be found at :
"A short and efficient preparation of alpha,p-dimethylstyrene from citral."
Barton, Derek H. R. / Parekh, Shyamal I.
Synthetic communications 19, 19, 3353-3361 (1989)
Post 490214 (Vitus_Verdegast: "wanted, alive and well :)", Novel Discourse)

If we have p-cymene and chromyl chloride at hand, it can be used to make 2-phenylpropanal (hydratropic aldehyde):
Post 427944 (lugh: "Hydratropaldehyde", Stimulants)
https://www.rhodium.ws/chemistry/2-phenylpropanal.html
V. Miller and Rohde Ber D Chem Gesell 24 1359 (1889) at http://gallica.bnf.fr/PeriosListe.htm

P2P from 2-phenylpropanal:
https://www.rhodium.ws/chemistry/2-phenylpropanal.html
Post 319139 (Jan1983: "P2P / Hydratropic Acid", Stimulants)
Post 343493 (BooWho: "Hydratropic--->p2p Success!", Stimulants)

In the same way that 2-phenylpropanal can be obtained from oxidation of alpha-methylstyrene, one should be able to obtain 4-methylhydratropic aldehyde from p-alpha-dimethylstyrene.

4-Methylamphetamine is described briefly in PiHKaL (#54 2,5-DMA):
"All three isomers of monomethylamphetamine have also been looked at in man. The ortho- and meta-isomers, 2-methyl- (and 3-methyl- ) amphetamine are weak anorexics. At doses of up to 150 milligrams orally, there were signs of stimulation noted--talkativeness and loss of appetite. The para-isomer, 4-methyl-amphetamine or Aptrol, is more potent. At 75 milligrams (orally, in man) there is clear adrenergic stimulation, and at twice this dosage there are signs of mild toxicity such as salivation, coughing and vomiting. "
http://www.erowid.org/library/books_online/pihkal/pihkal054.shtml

I don't think anything is known about the effects of the N-methyl and N-ethyl analogues.

Also, alpha-methylstyrene is a precursor for prodine analogues:
Post 397865 (Aurelius: "US patent 2765315 Prodine and analogues", General Discourse)
Post 437741 (Bwiti: "Prodine Analog Via 2-Methyl-1-Butene..", Methods Discourse)

p-alpha-Dimethylstyrene could then give rise to 1-methyl-4-tolyl-4-propionoxypiperidine. I don't know anything about its activity nor its legal status.

http://www.movieconnection.it/schede/nosferatu.jpg

moo
(Hive Bee)
03-01-04 02:08
No 491934
      I like your find, but I also see one problem.

I like your find, but I also see one problem.

If we have p-cymene and chromyl chloride at hand, it can be used to make 2-phenylpropanal (hydratropic aldehyde)

Unfortunately that is only true for cumene, whereas cymene is 4-methylcumene, and would yield 2-(4-methylphenyl)-propanal assuming it is possible to avoid oxidation of the aromatic methyl group when using chromyl chloride. frown It is still a possibility for 4-Me-P2P though.

_{fear fear hate hate}

Vitus_Verdegast
(Hive Addict)
03-01-04 09:15
No 491983
User Picture       Aww..

(sound of Vitus kicking himself..)

Thanks moo!

Somehow I thought that p-cumene and p-cymene were synonyms crazy ..

http://www.movieconnection.it/schede/nosferatu.jpg

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	All 3 posts		Subject: Proposed route to P2P or 4-Me-P2P from citral		Please login to post		Down


		Vitus_Verdegast (Hive Addict) 03-01-04 00:39 No 491925				Proposed route to P2P or 4-Me-P2P from citral
						Citral is everywhere, it is present in good amounts in lemon grass oil, orange peel oil and other citrus fruits. Citral is abundantly used in the food, cosmetics and perfumery industry, it's even more cheap than Iraqi oil and practically unwatchable. Citral consists of a cis- isomer (citral-a or geranial) and a trans- isomer (citral-b or neral). First, we'll have a look at Tetrahedron (1970) vol 26 p. 4901-4913 (DOI:10.1016/S0040-4020(01)93142-4): Abstract The acid catalysed cyclization of citral gives p-cymene and p-alpha-dimethylstyrene. The ratio of the arenes is dependent both upon the pH of the reaction medium and upon the presence or complete absence of oxygen. At pH 1·8 in the presence of oxygen the yield of the styrene is at a maximum to the almost complete exclusion of p-cymene. I will give the experimental details here, if someone with access to the full-text PDF could post it here, it would be much appreciated. Since Semmler's original observations in 1891 of the cyclization of citral in the presence of KHSO₄, the reaction has been studied by many workers using a variety of acidic catalysts and reaction temperatures. Under all conditions a single stable end-product has been isolated and shown to be p-cymene. Now these authors found that a change in the pH of the reaction medium alters the rate of initial cyclization step but it also results indirectly in the formation of end products other than p-cymene. Under an atmosphere of oxygen at pH 1.8 the predominant stable end product of the cyclization of citral is p-alpha-dimethylstyrene. When citral in a solution at pH 1.8 was stirred for 22 hours in an atmosphere of nitrogen, there was obtained a mixture of: p-cymene : 81% p-alpha-dimethylstyrene: 16.6% alpha-menthadiene (?) : 0.7% alpha-phellandrene : 0.7% and 2 unknown componds, each one in 0.5% yield After 6 hours of stirring at pH 0.5 under nitrogen there was already obtained 79% p-cymene and only 10% p-alpha-dimethylstyrene. When citral in a solution at pH 1.8 was stirred for 22 hours in an atmosphere of oxygen, there was obtained a mixture of: p-alpha-dimethylstyrene : 79% p-cymene : 7.7% alpha-menthadiene (?) : 3.9% and three unknown compounds at 2.4, 2.2 and 1.9% yield. After 6 hours of stirring at pH 1.75 under oxygen there was obtained 69% p-alpha-dimethylstyrene and 3.8% p-cymene. Lower pH values gave lower yield of p-alpha-dimethylstyrene (19.8% at pH 0.4) but high yields of p-cymene instead (71.5% at pH 0.4). pH Values of 2.0 and greater gave chiefly piperitenol under nitrogen and unreacted citral under oxygen. Acid catalysed rearrangements Citral (0.94g, 1 mL) in an aqueous solution (10 mL) of known pH was vigorously stirred at 70° for a known period of time. The atmosphere above the reaction mixture was controlled by passing the gas (either "white spot" nitrogen, scrubbed by passage through Cr(II) solution, or O₂) through the reaction mixture at a constant rate. A mercury bubbler seal ensured a slight positive pressure of the gas in the reaction flask at all times. The reaction was quenched by rapidly cooling the mixture to 0° and the products and unreacted citral were extracted immediately with light petroleum (commercial light petroleum, bp. 30-40° (May and Baker) was fractionally distilled from P₂O₅ to give a fraction having a single GLC peak on the LAC 2R-446 column), 15 mL + 2x 5 mL. The combined extracts were made up to 25 mL and n-octanal (8 microliter) was added to a sample of the extracts (2 mL) and the composition of the sample analysed with a Perkin-Elmer F11 gas chromatograph. p-cymene from citral and KHSO₄ : F.W. Semmler, Ber. Deutsch. Chem. Gesell. 24, 202 (1891) Free full-text PDF can be found at : http://gallica.bnf.fr/PeriosListe.htm A practical route to p-alpha-dimethylstyrene can be found at : "A short and efficient preparation of alpha,p-dimethylstyrene from citral." Barton, Derek H. R. / Parekh, Shyamal I. Synthetic communications 19, 19, 3353-3361 (1989) Post 490214 (Vitus_Verdegast: "wanted, alive and well :)", Novel Discourse) If we have p-cymene and chromyl chloride at hand, it can be used to make 2-phenylpropanal (hydratropic aldehyde): Post 427944 (lugh: "Hydratropaldehyde", Stimulants) https://www.rhodium.ws/chemistry/2-phenylpropanal.html V. Miller and Rohde Ber D Chem Gesell 24 1359 (1889) at http://gallica.bnf.fr/PeriosListe.htm P2P from 2-phenylpropanal: https://www.rhodium.ws/chemistry/2-phenylpropanal.html Post 319139 (Jan1983: "P2P / Hydratropic Acid", Stimulants) Post 343493 (BooWho: "Hydratropic--->p2p Success!", Stimulants) In the same way that 2-phenylpropanal can be obtained from oxidation of alpha-methylstyrene, one should be able to obtain 4-methylhydratropic aldehyde from p-alpha-dimethylstyrene. 4-Methylamphetamine is described briefly in PiHKaL (#54 2,5-DMA): "All three isomers of monomethylamphetamine have also been looked at in man. The ortho- and meta-isomers, 2-methyl- (and 3-methyl- ) amphetamine are weak anorexics. At doses of up to 150 milligrams orally, there were signs of stimulation noted--talkativeness and loss of appetite. The para-isomer, 4-methyl-amphetamine or Aptrol, is more potent. At 75 milligrams (orally, in man) there is clear adrenergic stimulation, and at twice this dosage there are signs of mild toxicity such as salivation, coughing and vomiting. " http://www.erowid.org/library/books_online/pihkal/pihkal054.shtml I don't think anything is known about the effects of the N-methyl and N-ethyl analogues. Also, alpha-methylstyrene is a precursor for prodine analogues: Post 397865 (Aurelius: "US patent 2765315 Prodine and analogues", General Discourse) Post 437741 (Bwiti: "Prodine Analog Via 2-Methyl-1-Butene..", Methods Discourse) p-alpha-Dimethylstyrene could then give rise to 1-methyl-4-tolyl-4-propionoxypiperidine. I don't know anything about its activity nor its legal status. http://www.movieconnection.it/schede/nosferatu.jpg



		moo (Hive Bee) 03-01-04 02:08 No 491934				I like your find, but I also see one problem.
						I like your find, but I also see one problem. If we have p-cymene and chromyl chloride at hand, it can be used to make 2-phenylpropanal (hydratropic aldehyde) Unfortunately that is only true for cumene, whereas cymene is 4-methylcumene, and would yield 2-(4-methylphenyl)-propanal assuming it is possible to avoid oxidation of the aromatic methyl group when using chromyl chloride. It is still a possibility for 4-Me-P2P though. _{fear fear hate hate}



		Vitus_Verdegast (Hive Addict) 03-01-04 09:15 No 491983				Aww..
						(sound of Vitus kicking himself..) Thanks moo! Somehow I thought that p-cumene and p-cymene were synonyms .. http://www.movieconnection.it/schede/nosferatu.jpg

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