ORGANIC CHEMISTRY

SYNTHESIS OF FLUORINE-CONTAINING METHOXY-1,3-DIKETONES

.METHODS OF SYNTHESIS

I. E. Sokolov, S. I. Shergina, and A. S. Zanina UDC 542.951.t:547.572.6:547.314

A method is proposed for the synthesis of fluorine-containing methoxy-l,3-diketones by hydrolysis of N-phenylamino- atkenyl ketones, produced by the reaction of aniline and the respective methoxyalkynyl ketone in dioxane. With methanol an imine is also formed, and methyl trifluoroacetate is eliminated.

Keywords: Synthesis, fluorine, 1,3-diketones.

In order to study the properties of methoxy-l,3-diketones and to increase the volatility of the chelates of certain metals

where 1,3-diketones are used as ligands we developed a method for the synthesis of partially fluorinated methoxy-l,3-diketones.

To convert the previously described [1] acetylenic ketones (I) into the diketones (3) we used the reaction of compound 1 with

aniline followed by hydrolysis of the obtained N-phenylaminoalkenyl ketones (2) with hydrochloric acid.

CF:,--f;( t--C~C--C(OMeJRIV u~S~,h__.__, (;F~--(;(~--(:I-t =C(H NPh)--C(OMe)Rf~" ( | a - c t (2a- -e}

~,1~o, H + - - - - * C F:,--CO--(; H~--CO~(;(OM e)tl I/"

(an e)

~I=H'=CH.,(a) : I/=I;H:~, tl '=n-(;~ll,~(b); II- t / '=(C[t~)~,(e)

The addition of aniline to the acetylenic ketones t was realized in methanol and dioxane. With dioxane the N-phenyt-

aminoalkenyl ketones 2 were the only reaction products (yields 80-89%), and their hydrolysis with a dilute solution of hydrogen chloride in alcohol gave the fi-diketones with yields of 75-86%.

However, when the reaction was conducted in methanol, the imine RR'C(OMe)C(Me)=NPh (4) was obtained in

addition to compound 2. According to GLC, the initially formed aminovinyl ketone 2 is split, and the concentration of the imine

4 in the reaction mixture is increased at the same time. In the synthesis of compound 2e the imine 4c was isoIated as the only

reaction produ~.t, and its structure was confirmed by the data from elemental analysis and tR and PMR spectroscopy and by its

production during hydrolysis of the ketone 5c. The imine 4c and ketone 5c are fully identical in their properties with the

analogous compounds obtained by an alternative synthesis according to the following scheme:

(~Ne xzso, OMe OMe t6) (5e) t4e/

The anomalous path in the nucleophilic addition of the amine to the acetylenic ketones in methanol can be explained by

the presence of a strong electron-withdrawing group in the initial molecule, since such an effect was not observed earlier during

the production of aminovinyl ketones with similar structure but without the fluorine atoms [2].

The presence of the trifluoromethyl group at the a position to the carbonyl probably promotes acetalization of the N- phenylaminoalkenyl ketone 2c.

Institute of Chemical Kinetics and Combustion, Siberian Branch, Russian Academy of Sciences, 630090 Novosibirsk.

Translated from lzvestiya Akademii Nauk, Seriya Khimicheskaya, No. 6, pp. 1390-1392, June, 1992. Original article submitted July 18, 1991.

1063-5211/92/4106-1087512.50 ©1993 Plenum Publishing Corporation 1087

TABLE 1. Properties of N-Phenylaminoalkenyl Ketone C F 3 - C O - C H =

C ( H N P h ) - C ( O M e ) R R ' and ~-Diketones C F 3 - C O - C H 2 - C O - C ( O M e ) R R '

Com- pound

2b

2e

3a

3b

3e

4¢

5¢

Yield,l Bp' 09 (P' t f "

84.fi

88.7

80.0

75.1

78.2

86.0

8.4.8

78.0

Found/Calculated, %

46-47 (pet .e~her)

170-173 (3)

76-77 (pe t . e the r )

84-85 (75) t2o it5)

97-98 (15)

152-154 (13) 105 (35)

58.55

64.02

62.64

45.28

55.it

52.2i

78.01

69.02

5.62

7.56 7.'55-i

6.20 6.t6 5.22

7.66

6.01 k-b-g 9.03

t0.t~

4.64 ,,.'qTff

3.70

4.27 4.28

6.01

Molecular formula

C,, H ,~()~ Fs

C,~H~O~F~

C,~H2aO~Fz

Cslt,,OaF3

C,:JI~,O.Ws

C,, It,~().~F3

C,.dl2,O

C~|l,sOz

HNPh H--(~--Me NPh t t - ~ ) - Me

=CH " C--CFs ~ 2c + MeOH ~.... ~"

O._ o NPh (IMe NPh

1i

} " " " ( " OMe i OMe ()H ()

It was noticed that compounds 2a-c can be arranged in the following order according to the ease of cleavage in relation

to the structure of the radicals R and R' : 2c > 2b > 2a.

The structure of the newly obtained compounds was confirmed by elemental analysis and by the presence of absorption

bands for compounds 2a-c at 1590, 1600 (C=C), 1650, and 1660 (C=O) and for compounds (3a-c) at 1720 cm -1 (C=O) in the IR

spectra.

EXPERIMENTAL

The PMR spectra were recorded on a Bruker AM-250 spectrometer in deuterochloroform with reference to HMDS. The

IR spectra were recorded in chloroform on a UR-20 spectrometer. Gas-liquid chromatography was conducted on a Chrom 5

instrument with a flame-ionization detector (360 x 0.4-cm column, 5% of SE-30 in Inerton AW, nitrogen, 140-180°C).

The acetylenic ketones l a -e were obtained according to the method in [1]. The yields and constants of the newly

synthesized compounds are given in Table 1. 4-(Phenylamino)-4-(1.methoxycyclohexyl)-l , l , l- trifluoro-3-buten-2-one (2e). To a solution of 40.0 g (0.17 mole) of

compound l c in 200 ml of dioxane was added 18.6 g (0.2 mole) of aniline. The mixture was stirred at 60°C for 3 h, and 44.5 g

of compound 2c (yield 80.0%) was isolated by distillation. PMR spectrum (deuterochloroform, 5, ppm): 1.49 m [10H, (CH2)5];

3.1 s (3H, MeO), 5.82 s (1H, HC=C); 7.39 m (5H, NPh); 12.67 s (1H, H . . . O ) . Compounds 2a,b were obtained similarly.

4-(1-Methoxycyelohexyl)-l , l , l- trifluoro-2,4-butanedione (3c). To a solution of 44.0 g (0.14 mole) of compound 2c in 200

ml of dioxane was added 40 ml of a 15% solution of hydrogen chloride. The mixture was stirred at 60-700C for 3 h. It was then

cooled and extracted with toluene. The organic layer was washed with water and dried over calcium chloride. The solvent was

distilled, and the residue was distilled. We obtained 30.7 g (yield 86.0%) of compound 3e. PMR spectrum (deuterochloroform, 6, ppm): 1.49 m [10H, (CH2)5]; 2.08 s (2H, CH2); 3.26 s (3H, MeO); 6.46 s (1H, HC=C); 12.3 s (1H, H . . . O ) . The diketones

3a,b were obtained similarly.

1088

1-Iminophenyl-l-(1-methoxycyclohexyl)ethane (4c). To a solution of 10.0 g (0.04 mole) of compound lc in 100 ml of

methanol was added 0.05 mole of aniline. The mixture was stirred at the boiling point for 4 h. The methanol was distilled, and

the product was distilled. We obtained 9.8 g of compound 4c. PMR spectrum (deuterochloroform, d, ppm): 1.45 m [10H,

(CH2)5]; 1.6 s (3H, Me); 3.02 s (3H, MeO); 6.75 m (5H, NPh). The imine 4c (9.6 g) was obtained by an alternative method from

7.3 g (0.05 mole) of compound 5c and 5.2 g of aniline with a yield of 83.0% by the method in [4].

1-(1-Methoxycyclohexyl)ethan-l-one (5c). Tile compound was obtained by the hydrolysis of 11.5 g (0.05 mote) of the

imine 4c by the method described in [2]. PMR spectrum (deuterochloroform, c3, ppm): 1.49 m [10H, (CH2)5]; 2.11 s (3H,

MeCO); 3.14 s (3H, MeO). The analogous compound was obtained with a yield of 78.0% during the hydration of compound 6c

[3].

LITERATURE CITED

t .

2.

3.

4.

s. [. Shergina, I. E. Sokolov, and A. S. Zanina, Izv. Akad. Nauk, Set. Khim., No. t, 158 (1992).

I. L. Kotlyarevskii, A. S. Zanina, S. I. Shergina, I. E. Sokotov, E. M. Shvarts, R. T. tgnash, and P. N. Tet'zhenskaya, Izv. Akad. Nauk, Ser. Khim, No. 3, 621 (1987).

A. S. Zanina, S. I. Shergina, I. E. Sokolov, G. N. Khabibulina, A. A. Kirchanov, and I. L. Kotlyarevskii, Izv. Akad. Nauk, Ser. Khim., No. t2, 2781 (1977).

D. G. Norton and V. E. Haury, J. Org. Chem., [9, 1054 (t954).

S Y N T H E S I S AND T R A N S F O R M A T I O N S O F M E T A L L O C Y C L E S .

9.* R E G I O S E L E C T I V E AND S T E R E O S E L E C T I V E S Y N T H E S I S

O F A I - S U B S T I T U T E D t r a n s - 3 , 4 - D I A L K Y L A L U M I N O C Y C L O P E N T A N E S

CATALYZED BY (@-CsH5)zZrCI 2

U. M. Dzhemi lev , A. G. Ib rag imov , A. B. Morozov,

R. R. Muslukhov, and G. A. Tolstikov UDC 542.97+547.5t4+547.256.2

A new slereoselective method is developed for #w synthesis of 1-chioro-, 1-a!koxy-, and l-N,N-dialkylaminoatummo- cyclopenmnes front a-olefins, metallic magnesium, and aluminum halides (AICI3, RO-AICI;~ R2N.AICI2) in the

presence of catalytic amounts of Cp2ZrCl 2 (Cp = ~75-C5Hd. The products from hydrolysis and deuterolysis of the Al-substituted 3,4-dialkylaluminocyclopentanes (ACP) have the threo configuration.

Keywords: Organoatuminum compounds, organozirconium compounds, catalysts, ofefins, mag~nesium, ~yn#wsis, hydrolysis, deuterolysis, alkoxides, aluminum chloride, amides.

Earlier we proposed a regioselective method for the synthesis of mono- and disubstituted aluminocyclopentanes starting

from c~-olefins and alkylalanes with catalytic amounts of Cp2ZrC12 [1]. In a development of these researches into the catalytic

cyclometallation of olefins by alkylalanes in the presence of Cp2ZrC12 and also to develop effective methods for the synthesis of

1-halogeno-, 1-alko~'-, and 1-dialkylaminoaluminocyclopentanes we studied for the first time the reaction of ~z-olefins with

aluminum halides, alkoxides, and amides (A1C13, RO-A1CI2, R2N.A!CI2) in the presence of magnesium and catalytic amounts of Cp2ZrC12. 1-Hexene and 5-methyl-l-hexene were used as olefins.

*For Communicalion 8, see [1].

Institute of Organic Chemistry, Urals Branch, Russian Academy of Sciences, 450054 Ufa. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 6, pp. 1393-1397, June, 1992. Original article submitted March 11, 1991.

1063-5211/92/4106-1089512.50 ©1993 Plenum Publishing Corporation 1089