Post 108370 (missing)
(dormouse: "Synthesis of asarone from eugenol methyl ether -Labrat", Novel Discourse) - Here follows the actual article (I heard of ppl with too much clove oil to handle ;) )CH--CH==CH2 CH--CH==CH2 CH--CH==CH2
| | |
C MeO C C
/ \ \ / \ / \
C C H--C C MeO--C C
| | -2e, 2 MeOH | | H+ | |
C C--OMe -------------> C C--OMe ----------> C C--OMe
\ / -2H+ \ / \ - MeOH \ /
C C OMe C
| | |
OMe OMe OMe
(2) (3) (1)
Intermediate (3) was isolated by work-up under alkaline conditions and characterised by 1H NMR. When analysed by GC/MS (3) gave a peak the at highest mass m/z 194 instead of the expected 240. This is probably due to a fragmentation, in which a molecule of dimethyl ether is lost, and (3) yields (4). [note: fragmentation and molecule (4) not shown].
The g-asarone obtained was isomerized in alkaline solution quantitatively3 into a 5:1 mixture of (E)- and (Z)-2,4,5-trimethoxypropenylbenzenes; the (E) isomer is important as a precursor in a synthesis of magnosalicin.6
As the alkaline isomerization of g-asarone showed to be very time consuming, attempts to prepare (E)-2,4,5-trimethoxybenzene via anodic oxidation directly from methyl isoeugenol (5) were made. However no nuclear methoxylation product could be isolated. In a typical experiment, the electrolysis of a solution of (5) (5.7 mmoles) in MeOH (60 mL) containing NaClO4 (6 mmoles) and NaOH (26.0 mmoles) at room temperature (80 mA, 00.91 Acm-2, 2F/mol), after work-up as described for methyl-eugenol (2), afforded two products derived from the side-chain methoxylation of (5): 1,2-dimethoxy-1-(3,4-dimethoxyphenyl) propane (6) (2.85 mmoles, 50%, erythro/threo, 2.5:1) and 1-(3,4-dimethoxyphenyl)-2-methoxy-propanol (7) (1.14 mmoles, 20%, erythro/threo, 2:1). Both structures were assigned based on GC/MS, IR and 1H/13C NMR measurements.
OMe OMe OH OMe
| | | |
CH==CH--CH3 CH--CH--CH3 CH--CH--CH2
| | |
C C C
/ \ / \ / \
C C C C C C
| | -2e, 2 MeOH | | + | |
C C--OMe -------------> C C--OMe C C--OMe
\ / \ / \ /
C C C
| | |
OMe OMe OMe
(5) (6) (7)
Eugenol (8) when oxidized under similar conditions as for (2), but to 1F/mol afforded dehydrodieugenol (9)7 in almost quanitative yield. This electrochemical dimerization has been reported8 but substituting NaClO4 for LiClO4 enabled us to use solutions with eugenol concentrations of up to 0.1 M which is ten times the one originally employed. With LiClO4 and 0.1 M of eugenol the lithium salt of (9) is formed on the electrode impeding the passage of current.
CH--CH==CH3 H2C==CH--CH CH--CH==CH2
| | |
C C C
/ \ / \ / \
C C C C C C
| | -2e, -2 H+ | | | |
C C--OMe -------------> MeO--C C--C C--OMe
\ / \ / \ /
C C C
| | |
OH OH OH
(8) (9)
Acknowledgements: We are grateful to the Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq) for a scholarship (RRV) and to Programa de Apoio as Desenvolvimento Cientifico e Tecnologico (PADCT) for financial support.
References:
1. ON Devgan, MM Bokadia, Aust J Chem 21 (1968) 3001
2. OR Gottlieb, AI de Rocha, Phytochem 11 (1972) 1861
3. AT Shulgin, Can J Chem 43 (1965) 3437
4. For leading references see S Torii, "Electroorganic synthesis: methods and applications" Part 1: Oxidations, monographs in modern chemistry, Vol 15, Kodansha, Tokyo and VCH, Weinheim, 1985.
5. NL Weinberg, B Belleau, Tetrahedron 29 (1973) 279
6. K Mori, M Komatsu, M Kido, K Nakagawa, Tetrahedron 42 (1986) 523
7. AF Dias, Phytochem 27 (1988) 3008
8. A Nishiyama, H Eto, Y Terada, M Iguchi, S Yamamura, Chem Pharm Bull 31 (1983) 2820
.: THE END :.
I'm not a specialist in electrochemistry, but I'm sure there are bees who are. This article is intended for them. Enjoy.
Also note that The only reported synthesis of (1) is based on the general... is not completely true, not even for 1989. I've seen several alfa/beta and gamma-asarone synthesis procedures. There even is a procedure involving Elbs persulfate oxidation, but the yields are less then 10%.
Post 218257 (https://www.thevespiary.org/talk/index.php?topic=11362.msg21825700#msg21825700)
(PolytheneSam: "ArOR, Alternatives to dimethyl sulfate", Novel Discourse)Post 347768 (https://www.thevespiary.org/talk/index.php?topic=11710.msg34776800#msg34776800)
(bottleneck: "1,4-Dimethoxy in two steps from benzene", Novel Discourse)Patent US4657700 (http://l2.espacenet.com/dips/viewer?PN=US4657700&CY=gb&LG=en&DB=EPD)
Example 1
100 g of ethylvanillyl alcohol (4-hydroxy-3-ethoxybenzyl alcohol) are dissolved in 200 ml of methanol. The solution is treated with 10 g of sodium hydrogen sulphate and a knife tip of hydroquinone. The mixture is firstly heated to 50.degree. C. for 2 minutes and left to cool again to room temperature. The methanolic solution is now poured into 85 ml of a saturated sodium hydrogen carbonate solution. The methyl alcohol is distilled off in vacuo, the residue is taken up in toluene, the organic solution is washed neutral with water and evaporated. The residue (95.5 g) is fractionally distilled. There are obtained 61.1 g of chemically and olfactorily pure 4-hydroxy-3-ethoxybenzyl methyl ether; b.p.=77.degree. C./0.03 mmHg; d.sub.4.sup.20
=1.1084; n.sub.D.sup.20 =1.529.
Yield: 56.3%.
(Note that it is a benzyl methyl ether here (above) and not a phenol ether, but it may suggest possibilities.)
Notice the part in column 7 of
Patent US5214034 (http://l2.espacenet.com/dips/viewer?PN=US5214034&CY=gb&LG=en&DB=EPD)
Examples of the acid catalyst which may be used in this method include mineral acids such as sulfuric acid, phosphoric acid, hydrogen halide etc., Lewis acids such as anhydrous aluminium chloride, zinc chloride, iron chloride, titanium tetrachloride, tin tetrachloride, boron fluoride etc., organic sulfonic acids such as p-toluenesulfonic acid, methanesulfonic acid, dodecylsulfonic acid etc., organotin compounds such as dibutyltin oxide, dibutyltin dilaurate, dimethyltin dichloride etc., metal alkoxides such as titanium isopropoxide, cation exchange resin and the like.
and example 10
EXAMPLE 10
Preparation of 5,2,2-trimethyl-1,3-benzodioxol
A mixture of 6.21 g (50 mM) of homocatechol (commercially available special grade reagent), 15 ml of acetone, 30 mg of
p-toluenesulfonic acid monohydrate and 15 ml of benzene was heated under reflux for 48 hours with stirring. During the
reaction, a three-component azeotropic mixture composed of acetone, benzene and water as a by-product was passed through a molecular sieve packed column to remove only the by-product water. Acetone and benzene were returned to the reaction system.
After completing the reaction, the reaction mixture was distilled in vacuum to obtain 7.88 g (48 mM) of
5,2,2-trimethyl-1,3-benzodioxol as light brown liquid having a boiling point of 79.degree.-80.degree. C./9 mmHg.
IR Spectrum .nu..sub.max.sup.neat cm.sup.-1 : 2990, 2920, 2870, 1500, 1440, 1380, 1350, 1255, 1230, 1155, 1120, 1070,
1040, 980, 930, 880, 840, 825, 795, 745.
NMR Spectrum [C.sub.10 H.sub.12 O.sub.2 ]:
______________________________________
C H
______________________________________
Calculated, (%) 73.15 7.37
Found (%) 72.87 7.13
______________________________________
Post 227445 (https://www.thevespiary.org/talk/index.php?topic=11362.msg22744500#msg22744500)
see also
which refers to Russian patent 197613 which was found with the following English abstract:
PHENOL METHYL ETHERS are conventionally prepd, by acid esterification
In the proposed method the process is improved by using a cation-exchange resin as catalyst. In an example, 0.5 mole phenol, 0.5 -2.0 mole methanol and 23 g. resin are heated for 10 hrs. at 110° C. The product is filtered and fractionated, yield of anisole. 98% theoretical.
Post 422597 (https://www.thevespiary.org/talk/index.php?topic=7155.msg42259700#msg42259700)
(PolytheneSam: "CA4:905", Chemistry Discourse)Post 418138 (https://www.thevespiary.org/talk/index.php?topic=11802.msg41813800#msg41813800)
(bottleneck: "Etherification by cat. amounts of a tosylate?", Novel Discourse)