H Y D R O G E N A T I O N OF 2 , 6 - H E P T A N E D I O N E ON P L A T I N I Z E D CARBON

(UDC 542. 97)

N. I . S h u i k i n and G. K. V a s i l e v s k a y a

N. D. Zelinskii Institute of Organic Chemistry, Academy of Sciences, USSR Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 3, pp. 557-558, March, 1964 Original article submitted July 26, 1963

In previous communications we demonstrated that on hydrogenating 2-alkyl-5-acylfurans in the presence of a number of catalysts they are converted into homologs of tetrahydropyran and cyclohexanone [1, 2]. We proposed that the homologs of both tetrahydropyran and cyclohexanone are formed under the hydrogenation conditions as a result of the secondary conversion of 5 -diketones formed, in turn, during the hydrogenolysis of the furan ring across the C - O bond nearest to the carbonyl group.

R - ~ - - R ' = R--C--C--C--C--C--WII II O o O

In fact, on hydrogenating 2-alkyl-5-acylfurans on platinized asbestos, in whose presence the cyclization reac- tion of the initially formed diketones proceeds relatively slowly, we succeeded in preparing the corresponding 6 -dike- tones in yields up to 40o [3]. It was previously known that intramolecular cyclization of diketones with the splitting offofwater proceeds rather easily in the presence of acids or alkali [4, 5]

O I1

R - - C - - C- - C - - C - - R'.-~ R" - - C II II

0 0 / R'

However, until now it had not been shown that a similar cyclization occurs under the conditions of catalytic hydrogenation. After carrying out the hydrogenation of 2,6-heptanedione in the vapor phase over Pt -C, we were convinced that it undergoes conversion in two directions: 1) hydrogenation to 2,6-heptanediol followed by its de- hydration of 2,6-dimethyltetrahydropyran, and 2) cyclization to 3-methyl-2-cyclohexenone,which under the hydro- genation conditions is converted to 3-methylcyclohexanone and 3-methylcyclohexanoL

/ \ s [ c - c - c - c - c - c - c ] ~ [ A

c - - c - c - c - c c - - c \ I I / ~ OH OH C O C II II O O

xa

_. --C i_ --C

II II I O O OH

Thus, it can be considered as proven that 6 -diketones are intermediates in the hydrogenation of 2-alkyl-5-

acylfurans to homologs of tetrahydropyran and cyclohexanone.

EX PERI MEN TA L

2-Methyl-5-acetylfuran was prepared by aeetylating 2-methylfuran in the presence of phosphoric acid. Hydro- genation of 2-methyl-5-acetylfuran on Pt-asbestos (10% Pt) at 200* and a flow rate of 0,1 hour "I resulted in the

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formation of 2,6-heptanedione in 35% yield, possessing the following properties: b. p. 112-114 ~ (2 mm); m. p. 32-33~ dioxime, m. p. 87 ~ 2,6-Heptanedione, previously dissolved in cyclohexane, was hydrogenated over platinized carbon at 200 ~ and a flow rate of 0.1 hour -I. The following substances were isolated from products of catalysis: 1) 2 ,6-di - methyltetrahydropyran, b. p. 113-114 ~ n}~ 1.4180, d~ 8384; yield 40% based on the products of catalysis; 2) 3- methylcyclohexanone, b. p. 56-58 ~ (10 ram), n~ 1.4461, d~ 0.9133; 43.5% yield based on the products of catalysis and 3) 3-methylcyclohexanol , b. p. 40-42 ~ (3 ram), n~ 1.4570, d24 ~ 0.9164; 15~ yield.

S U M M A R Y

1. On hydrogenation at 200 ~ over P t -C , 2,6-heptanedione is converted to 2,6-dimethyltetrahydropyran, 3- methylcyclohexanone and 3-methylcyclohexanol .

2. The formation of 2,6-heptanedione is an intermediate step in the conversion of 2-methyl -5-acety l furan to 3-methylcyclohexanone and 2,6-dimethyltetrahydropyran.

L I T E R A T U R E C I T E D

1. I . F . Bel'skii, N. I. Shuikin, and G. K. Vasilevskaya, Dokl. AN SSSR, 136, 591 (1961). 2. I . F . Bel'skii, N. I. Shuikin, G. K. Vasilevskaya, and G. K. Gaivoronskaya, Izv. AN SSSR. Otd. khim. n., 1962,

1650. 3. N.I. Shuikin, I. F. Bel'skii, and G. K. Vasilevskaya, Izv. AN SSSR. Otd. khim. n., 1961, 363. 4. R.G. Fargher and W. H. Perkin, J. Chem. Soc., 105, 1353 (1914). 5. O. Dann, E. Pietschmann, and W. Dimling, Arch. Pharmazie, 292164, 508 (1959); RZhKhim, 1960, No. 69443.

All abbreviations of periodicals in the above bibliography are letter-by-letter transliter- ations of the abbreviations as given in the original Russian journal. Some or all o[ this peri-

odical l i terature may well be available in Engl i sh translation. A complete list of the cover-to- cover English translations a p p e a r s at the back of this issue.

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