quinones as starting material
(Rated as: excellent)
otto has digged up 2 papers dealing with the conversion of quinones to useful compounds.
1)Photoacylation of Electron-Rich Quinones: An Application of the "Photo-Friedel-Crafts Reaction"
in Synthesis 2001, No.8, pp 1275-1279.
abstract: irradiation of substituted 1,4-benzo- or 1,4-naphtoquinones in the presence of several aldehydes resulted in the formation of acylated hydroquinones in good yields...
general procedure: a solution of the quinone and the aldehyde in t-BuOH or benzene was carefully degassed with Ar and irradiated for 18 h at r.t. the solvent was removed in vacuo and the product isolated by column chromatography.
(yields given were mostly in the 60 to 90% range)
they used sunlight in some examples and it worked. so one could prepare 2-Acetoxy-1,4-Hydroquinone from benzoquinone and acetaldehyde.
2)Quinonic Enaminones; Synthesis of New Dialkylaminovinyl and Bis(dialkylaminovinyl) Darivatives of Quinonesin Synthesis 2000, No 8, pp 1087-1090.
abstract: the reaction of halogenated quinones with a variety of secondary amines in the presence of acetaldehyde proceeds via intermediate formation of enamines and produces mono quinonic enaminones...
that means in one example they used tetrachloro-1,4-benzoquinone (chloranil) and reacted it w/ acetaldehyde and diethylamine to obtain a trichloro-1,4-benzoquinone, bearing a beta-ethylene-(N,N-diethyl)-amino-group instead of the lost chlorine. imagine the sidechain of mescalin, add double bond in between the carbons and attach two ethyl groups to the nitrogen. so this chain can be added to halo-1,4-benzoquinones!
general procedure: to a solution of tetrahalogenated 1,4-benzoquinone or 2,3-dichloronaphtoquinone (4.4 mmol) in toluene (60 ml) was added a mixture of acetaldehyde (4.4 mmol) and a secondary amine (8.8 mmol) in toluene (20 ml). the mixture was stirred at r.t. until disappearance of starting quinone (TLC). the blue colored solution was evaporated under reduced pressure and the resulting solid was purified by column chromatography using DCM eluent. the products were recrystalized from hexane or PE (bp 60-80°C).
my immediate idea on this was:
1,4-HQ --> 2,5-dibromo-1,4-HQ --> 2,5-dibromo-1,4-benzoquinone-->2-beta
p.s. pdf's again from www.thieme-connect.com
quinones to acylhydroquinones
(Rated as: excellent)
I found some more interesting related stuff. Perhaps even more interesting.
Quinone photochemistry. A general synthesis of acylhydroquinones.
J. Org. Chem. (1992), 57(11), 3256-7.
Acylhydroquinones were prepd. in good yields by the irradn. of solns. of quinones and aldehydes. Aliph., unsatd. and arom. aldehydes can be employed. The photochem. reaction of benzoquinone with butanal gave 1-(2,5-dihydroxyphenyl)-1-butanone in 82% yield. The reaction with 2-butenal gave 1-(2,5-dihydroxyphenyl)-2-buten-1-one in 52% yield; no intramol. cyclization occurred in this reaction.
Green photochemistry: the solar-chemical 'Photo-Friedel-Crafts acylation' of quinones.
Green Chem. (2001), 3(5), 224-228.
The photoreactions between 1,4-quinones (1 and 4) and aldehydes (2 and 5), yielding acylated hydroquinones as sole products, were investigated under artificial and solar irradn. conditions. Three different solar reactors were used for the photochem. syntheses with sunlight (PROPHIS, CPC and a flat bed reactor), and the CPC system was found to be the most robust one in terms of weather dependence. The solar reactions can be easily performed on a half-kilogram scale using cheap and com. available starting materials.
A photochemical alternative to the Friedel-Crafts reaction.
Kraus, George A.; Kirihara, Masayuki; Wu, Yusheng.
ACS Symp. Ser. (1994), 577(Benign by Design), 76-83.
The Friedel-Crafts reaction, a widely used reaction in both industrial and academic labs., produces several byproducts which must be handled as pollutants. An alternative which involves the photochem.-mediated reaction of an aldehyde with a quinone is described. This alternative chem. can be applied to direct syntheses of the ring systems of the benzodiazepines and benzoxepins.
They synth diazepam(new Valium synth), 2,5-Dihydroxybenzophenone, 1-(2,5-dihydroxyphenyl)-1-Butanone plus more.
Hmmm this paper might bee good!!!
Performing these additions chemically?
Alkylation of quinones with radicals. Generation of radicals in redox reactions.
Jacobsen, Niels; Torssell, Kurt.
Justus Liebigs Ann. Chem. (1972), 763 135-47. Abstract
Scavenging of C radicals, generated by H abstraction of ether solvents by OH radicals, with quinones gave the alkylquinones I and II (R = alkoxyalkyl, tetrahydrofuryl, dioxanyl). High yields of I and II [R = Me2CH, Me3C, alkoxymethyl, benzyl, PhOCH2, HO2C(CH2)4, etc.] were also obtained by alkylation of quinones with C radicals generated by Ag+- and S2O82-catalyzed oxidative decarboxylation of 13 carboxylic acids. A homolytic alkylation mechanism via semiquinone radicals was proposed. About 26 alkylquinones were prepd.
Some of the compounds prepared are: 2-(Hydroxymethyl)-1,4-benzoquinone, 2-Phenoxymethyl-1,4-benzoquinone, ect
Photoalkylation of quinones with ethers
(Rated as: excellent)
Photoalkylation of quinones with ethers.
J. Photochem. Photobiol., A (1999), 129(1-2), 49-50.
The photoalkylation reactions of benzoquinone with a number of ethers was studied. Some unusual regioselectivities were observed.
A typical experiment is conducted as follows:
A round-bottom flask is charged with a teflon-coated stirring bar, ether and benzoquinone. Reactions were conducted using 10 mmol (1.08 g) of benzoquinone and 100 mmol (10 equivalents) of the ether. The flask is placed in a well-ventilated hood and irradiated with light from a medium pressure Hanovia lamp. The progress of the reaction is monitored by thin layer chromatographic analysis using commercially available thin layer chromatography plates coated with silica gel. When the limiting reagent (the starting quinone) has been consumed, the solvent is then removed in vacuo and all of the crude product is immediately purified by column chromatography using commercially available silica gel (flash chromatography) with a solvent mixture of ethyl acetate and hexanes.
Products are 2-(R)substituted benzoquinones and hydroquinone.
Ether: Methyl tert-butyl ether
Yeild (%): 40
R-: -CH2-O-CH2-CH2–O–CH- (the dioxane ring is intact)
Yeild (%): 10
Yeild (%): 34
Yeild (%): 34
Yeild (%): 14
Ether: Methyl benzyl ether
Yeild (%): 14
Ether: Ethyl benzyl ether
Yeild (%): 30
Ether: Diethyl ether
Yeild (%): 26
The same oxidation process is occurring in our system and is responsible for the modest yields and the unusual regioselectivity. An examination of the product mixture from the reaction of benzoquinone with methyl benzyl ether using gas chromatography showed that benzaldehyde, a product of the oxidation of the benzylic radical followed by fragmentation, was produced in 11-17% yield and that benzoic acid (presumably derived from oxidation of benzaldehyde) was also produced in 11-17% yield.
As the results of Table 1 show, the addition reactions show surprising regioselectivities with dialkyl ethers. Many of the isolated yields are modest; nevertheless, the starting materials are readily available. Additionally, the experimental conditions are operationally convenient.
Photoreaction of 1,4-naphthoquinone and 1,4-dioxane. 2-Dioxanyl-1,4-naphthoquinone synthesis.
Tetrahedron Lett. (1969), (15), 1169-72.
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