As already described in 1933 by Heinrich Hock, 1,2,3,4-tetrahydronaphthalene tends to autoxidize and gradually forms the 1-hydroperoxide with atmospheric oxygen.[7] The heavy metal ion catalyzed air oxidation of 1,2,3,4-tetrahydronaphthalene with Cr3+[8] or Cu2+ in the liquid phase leads via the hydroperoxide to a mixture of the intermediate 1-tetralol and the final product 1-tetralone.[9]
The boiling points of the main component 1-tetralone (255-257 °C) and the minor component 1-tetralol (255 °C)[2] are virtually identical, the latter is therefore removed by a chemical reaction.[10]
By Friedel-Crafts reactions
The starting compound 4-phenylbutanoic acid is accessible from 3-benzoylpropanoic acid via catalytic hydrogenation, using a palladium contact catalyst.[5] 3-Benzoylpropanoic acid[11] itself can be obtained by a Haworth reaction (a variant of the Friedel-Crafts reaction) from benzene and succinic anhydride.
The intramolecular cyclization of 4-phenylbutanoic acid to 1-tetralone is catalyzed by polyphosphoric acid[5] and methanesulfonic acid.[12]
It has been described as a teaching experiment for chemistry lessons.[13] 4-Phenylbutanoic acid can also be quantitatively converted into 1-tetralone by heating in the presence of a strong Lewis acid catalyst such as bismuth(III)bis(trifluoromethanesulfonyl)amide[14] [Bi(NTf2)3], which is relatively easily accessible.[15]
The use of the acid chloride and tin(IV) chloride (SnCl4) allows significantly shorter reaction times than the Friedel-Crafts acylation with 4-phenylbutanoic acid.[10]
The AlCl3-catalyzed acylation of benzene with γ-butyrolactone produces 1-tetralone.[10]
Reactions
1-Tetralone can be reduced via a Birch reduction with lithium in liquid ammonia to 1,2,3,4-tetrahydronaphthalene.[17] The keto group can also be reduced to a secondary alcohol giving 1-tetralol, when a modified process is applied, using the addition of aqueous ammonium chloride solution after evaporation of the ammonia.[18]
With calcium in liquid ammonia, 1-tetralone is reduced to 1-tetralol at -33 °C in 81% yield.[19]
The methylene group in α-position to the keto group is particularly reactive and can be converted with formaldehyde (in the form of the trimeric trioxane) to 2-methylene-1-tetralone in the presence of the trifluoroacetic acid salt of N-methylaniline with yields up to 91% .
The 2-methylene ketone is stable at temperatures below -5 °C, but fully polymerizes at room temperature within 12 hours.[20]
In the Pfitzinger reaction of 1-tetralone with isatin, a compound called tetrofan (3,4-dihydro-1,2-benzacridine-5-carboxylic acid) is formed.
The reactivity of the α-methylene group is also exploited in the reaction of 1-tetralone with methanol at 270-290 °C, which produces via dehydrogenation and formation of the aromatic naphthalene ring system 2-methyl-1-naphthol in 66% yield.[21]
The oxime of 1-tetralone reacts with acetic anhydride leading to aromatization of the cycloalkanone ring. The resulting N-(1-naphthyl)acetamide[22] has biological properties akin to those of 2-(1-Naphthyl)acetic acid as a synthetic auxin.
The ruthenium(II)-catalyzed arylation of 1-tetralone using phenyl boronic acid neopentyl glycol ester gives 8-phenyl-1-tetralone in up to 86% yield.[24]
With 5-aminotetrazole and an aromatic aldehyde, 1-tetralone reacts in a multi-component reaction under microwave irradiation to form a four-membered heterocyclic ring system.[25]
Applications
By far the most important application of 1-tetralone is in the synthesis of 1-naphthol by aromatization, e.g. upon contact with platinum catalysts at 200 to 450 °C.[26]
^H. Hock; W. Susemihl (1933), "Autoxydation von Kohlenwasserstoffen: Über ein durch Autoxydation erhaltenes Tetrahydro-naphthalin-peroxyd (I. Mitteil.)", Ber. Dtsch. Chem. Ges. (in German), vol. 66, no. 1, pp. 61–68, doi:10.1002/cber.19330660113
^S. Bhattacharjee; Y.-R. Lee; W.-S. Ahn (2017), "Oxidation of tetraline to 1-tetralone over CrAPO-5", Korean J. Chem. Eng. (in German), vol. 34, no. 3, pp. 701–705, doi:10.1007/s11814-016-0310-4, S2CID100124813
^US 4473711, R.W. Coon, "Liquid-phase process for oxidation of tetralin", published 1984-09-25, assigned to Union Carbide Corp.
^L. F. Somerville, C. F. H. Allen (1933). "β-Benzoylpropionic acid". Org. Synth. 13: 12. doi:10.15227/orgsyn.013.0012.
^V. Premasagar; V.A. Palaniswamy; E.J. Eisenbraun (1981), "Methanesulfonic acid catalyzed cyclization of 3-arylpropanoic and 4-arylbutanoic acids to 1-indanones and 1-tetralones", J. Org. Chem., vol. 46, no. 14, pp. 2974–2976, doi:10.1021/jo00325a028
^S. Antoniotti; E. Dunach (2008), "Facile preparation of metallic triflates and triflimidates by oxidative dissolution of metal powders", Chem. Commun., vol. 8, no. 8, pp. 993–995, doi:10.1039/B717689A, PMID18283360
^D.-M. Cui; M. Kawamura; S. Shimada; T. Hayashi; M. Tanaka (2003), "Synthesis of 1-tetralones by intramolecular Friedel-Crafts reaction of 4-arylbutyric acids using Lewis acid catalysts", Tetrahedron Lett., vol. 44, no. 21, pp. 4007–4010, doi:10.1016/S0040-4039(03)00855-4
^H. Motiwala; R.H. Vekariya; J. Aubé (2015), "Intramolecular Friedel-Crafts acylation reaction promoted by 1,1,1,3,3,3-hexafluoro-2-propanol", Org. Lett. (in German), vol. 17, no. 21, pp. 5484–5487, doi:10.1021/acs.orglett.5b02851, PMID26496158
^S.S. Hall; S.D. Lipsky; F.J. McEnroe; A.P. Bartels (1971), "Lithium-ammonia Reduction of Aromatic Ketones to Aromatic Hydrocarbons", J. Org. Chem., vol. 38, no. 18, pp. 2588–2591, doi:10.1021/jo00817a004
^Z. Marcinow; P.W. Rabideau (1988), "Metal-Ammonia Reduction of α-Tetralone. Competition Between Ring Reduction, Carbonyl Reduction, and Dimer Formation", J. Org. Chem., vol. 53, no. 9, pp. 2117–2119, doi:10.1021/jo00244a054
^J.R. Hwu; Y.S. Wein; Y.-J. Leu (1996), "Calcium metal in liquid ammonia for selective reduction of organic compounds", J. Org. Chem. (in German), vol. 61, no. 4, pp. 1493–1499, doi:10.1021/jo951219c
^M.S. Newman; W.M. Hung (1973), "An improved aromatization of α-tetralone oximes to N-(1-naphthyl)acetamides", J. Org. Chem. (in German), vol. 38, no. 23, pp. 4073–4074, doi:10.1021/jo00987a029
^G.P. Kantin; M. Krasavin (2016), "Reaction of α-tetralone, 1H-tetrazol-5-amine, and aromatic aldehydes upon microwave irradiation – a convenient method for the synthesis of 5,6,7,12-tetrahydrobenzo[h]tetrazolo[5,1-b]quinazolines", Chem. Heterocycl. Compd. (in German), vol. 52, no. 11, pp. 918–922, doi:10.1007/s10593-017-1985-0, S2CID99144245
^DE 2421745, K. Kudo, T. Ohmae, A. Uno, "Verfahren zur Herstellung von α-Naphthol durch katalytische Dehydrierung von α-Tetralon", published 1975-11-20, assigned to Sumitomo Chemical Co., Ltd.