T R A N S F O R M A T I O N S OF n - B U T Y L P Y R I D I N E S IN THE P R E S E N C E

OF A L U M I N A - C H R O M I A C A T A L Y S T S

(UDC 542.97+ 547.82)

N. I . S h u i k i n , L. A. E r i v a n s k a y a , G. S. K o r o s t e l e v a , and A. P. P o l y a k o v

M. V. Lomonosov Moscow State University Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 12, pp. 2216-2218, December, 1965 Original article submitted April 20, 1965

A study of the transformation products of the 2- and 3-n-butylpyridines on alumina-chromia catalyst revealed that here the formation of a new C - C bond goes with much greater difficulty than in the case of n-butylbenzene [1] or 2-n-butylnaphthalene [2]. This is apparently associated not only with the lesser reactivity of the butylpyridines in the dehydrocyclization reaction, but also with a rapid poisoning of the catalyst, 2-n-Butylpyridine in contact with a lumina-chromia catalyst undergoes dehydrocyclization both at the nitrogen with the formation of indolizine, and at the carbon atom of the pyridine with the formation of quinoline, and also the removal of the alkyl group by crack-

ing.

/ ~ n - C ~ H , j

N

where R = H, CHa,C2H 5, C3f| 7

The indolizine was isolated in the pure state by the fractional distillation of the transformation products of 2-n-butylpyridine through a column with an efficiency of 35 theoretical plates, The quinoline was identified in the appropriate fraction of the catalyzate by gas-liquid chromatography and was isolated as the picrate. The butyl- pyridine was cracked to the extent of 50-55% at 570-600~ here the cleavage of the pyridine ring with the evolution of ammonia was also observed, 2-n-Butylpyridine also underwent profound cracking at 600 ~ in the absence of a catalyst; quinoline and indolizine were not isolated here, The transformation products of 3-n-butylpyridine on alu- mina-chromia catalyst (table) were also found to contain indolizine and quinoline (contaminated with indoles). 2- Methylpyridine was identified in the cracking products. It is possible that the indolizine was formed by a shift of the alkyl group to the 2-position of the pyridine and subsequent cyclization.

E X P E R I M E N T A L

The starting 2- and 3-n-butylpyridines were obtained by the reaction of phenyllithium, 2- or 3-picoline and propyl bromide [3]. The molar ratio of the reactants was 2 : 2 : 1, The picolines were distilled in advance through a column. The yield of 2-n-butylpyridine was 50-60% when based on n-propyl bromide.

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TABLE !. Transformations of 2- and 3-n-Bu[ylpyridine on Alumina-Cbxomia Catalyst

Starting n-butyl-

pyridine

gm- ~ra -

re, C

470

470 570 600 470 570

Yield- Space

of cat veloc-

ity, I a lyz- yri- h_ 1 ate, ine

wt. %

0.4 86.0

0.1 I 74.0 0.3 87.0 5.0

0.3 60.0 7.0:

0.I 70.0 1,0

0.2 60 5.0

2-n- Butylpyrid ine

Ditto Ditto Ditto

3-n- Butylpyrid ine Ditto

* Possibly 3-methylindolizine;

Composition of catalyzate based on GLC data, w~ %

J- Apparently 5,6,7,8 -tetrahydroquinoline~ SPyridine and its cracking products. * * Quinoline and indoles.

2-

pice-

line

9.0

20.0

19.0 3.0

5,0

2- 2-pro- I bu-- 3-

: thyl p y l - I t y l - ,ico- pyri- pyri- pyri- ine dine dine dine

3.0 ~-- 88.0 - -

~ 1 o1~ 17.0 T 30,01 17.0 23.0 1

- -- 55.0 I 19.0

38.0 28.0

3 - - - unidenti-

ethyl- feed sub- pyri- stances, b. tine I ). 150-170 ~

5.0 5.0

i t~176176 I 8.0

in- I unidenti'- Ified m a -

loci-I i �9 ~ _

10.0 .0

4.o I o,5 t 5.01 2.0 t 5.0**

q u i n o - line

5 , 0

15.0

2-n-Butylpyridine. B. p. 191.2-191.8 ~ (748 mm); d[ ~ 0.9186; n~ 1.4920; picrate, m. p. 94% Literature data [4]: b, p. 189-192~ d 15 0.9135; n~ 1.4869; picrate, m. p. 94 ~

zo 1.4914; d~ ~ 0.9009; picrate, m. p. 89-90 ~ Literature data 3-n-Butylpyridine. B. p. 201.5-202 ~ (740 ram); n D [5]:b. p. 80-81 ~ (8 ram); n~ 1.4917; d24 ~ 0.9114; picrate, m. p. 89.5-90%

The experiments were run in the conventional apparatus of the flow type in the presence of alumina-chromia catalyst (20% CrzO3) , in a stream of carrier gas (either nitrogen or hydrogen). The obtained catalyzates were first distilled in a nitrogen stream from a small Wurtz flask (at times together with absolute benzene in order to remove traces of moisture),, and then through a column with an efficiency of 38 theoretical plates. The ratio of the reaction products in the catalyzates depends on the experimental temperature used (see table). The fractions obtained after distillation through the column were analyzed by the gas-liquid chromatographic method using a katharometer as the detector, in a helium stream (30 ml /min) , on a column 2.2 meters long, filled with sodium chloride, on which 1% of dinonyl phthalate had been deposited. The fractions boiling up to 150 ~ were analyzed at 90 ~ the fractions with b. p. 150-200 ~ were analyzed at 121 ~ and the fractions with b. p. above 200 ~ were analyzed at 137 ~ The pres- ence of pyrrole compounds in the fractions was verified by the infrared spectra. The obtained compounds were iden- tified on the basis of their properties, the melting points of their picrates, and spectrally.

Indolizine, b. p. 202-202. 5 ~ (750 ram), melting point of sublimed product 73.5-74~ picrate, m. p. 96-98% The picrate of the indolizidine obtained by the hydrogenation of the indolizine in the presence of platinum dioxide had m. p. 227-228 ~ Found: N 15.55; 15.57. CI4H18N407. Calculated: N 15.82% Literature data [6]: b. p. 205 ~ m. p. 74 ~ [7]; picrate, m. p. 101 ~ [8]; indolizidine picrate, m. p. 2ao ~ The ultraviolet absorption spectrum (in meth- anol) had the absorption maxima characteristic for the indolizine system [9, 10]; k max, mg (log e): 238 (4.22), 268- 270 (3.65), 280 (3.63), 293 (3.64), 312 (3.01), 342-345 (3.19), 370 (2.97).

Quinoline was isolated from the appropriate fraction as the picrate with m. p. 202-203 ~ The mixed melting point with an authentic specimen was not depressed. Found: N 15.52; 15.6t. CIbHIoN407. Calculated: N 15.64%.

SUMMARY

Together with a partial cracking of the butyl group, 2-n-butylpyridine under the conditions of contact with

alumina-chromia catalyst at 500-600 ~ underwent dehydrocyclization at the nitrogen atom with the formation of

indolizine, and at the carbon atom with the formation of quinoline. Indolizine and quinoline were also identified in the transformation products of 3-n-butylpyridine.

1. 2.

LITERATURE C I T E D

S. S. Nametkin, M. I. Khotimskaya, and L. M. Rozenberg, Izv. AN SSSR, Otd. Khim. Nauk, 1947, 795. N. I. Shuikin, L. A. Erivanskaya, and Ai-Hsi Yang, Dokl. AN 8SSR, 133, 1125 (1960).

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3. C. Osuch and tL Levine, L A m e r . Chem. 8oc., 78, 1725 (1956). 4. G.J . Janz and tL Solomon, AnaIyt. Chem., 25, 454 (t953). 5. J .P. Wibaut and C. Hoogzand, Chem. Weekblad, 52, 357 (1956); Chem. Abstrs., 51_ 3593 (1957). 6. M. Scholtz, Chem. Bet., 45, 739 (1912). 7. O. Diels and K. Alder, Liebigs Arm. Chem., 498, 44 (1932). 8. G. IL Clemo and T. P. Metcalfe, J. Gaem. Soc., 1937, 1518, 9. G.R. Clemo, B. W. Fox, and IL Raper, I. Chem. Soc , 1953, 4173.

lO. w. L, F. Armarego, J. Chem. Soc., 1964, 4226.

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

odical l i terature may wel l be avai lable in E n g l i s h translation. A complete list of the cover-to- cover English translations appears at the back of this issue.

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