2598 J. Chem. SOC. (C), 1969

Heterocyclic Polyfluoro-compounds. Part XVII.l Ethanolysis of Per- f I uoro- (2-met hyl-2H-azirine) By R. E. Banks," D. Berry, and G . J. Moore, Chemistry Department, The University of Manchester Institute of

Perfluoro-(2-methyl-Z~-azirjne) reacts with ethanol to give ethyl 2-ethoxy-3,3,3-trifluoro-2-hydroxy- and 3,3,3-trifluoro-2,2-dihydroxy-propionate. These esters can also be obtained by treatment of 3.3.3-trifluoro- 2.2-dihydroxypropionic acid (trifluoropyruvic acid hydrate) with ethanol in the presence of hydrochloric acid.

THERMAL decomposition of perfluoropropenyl azide was the corresponding N-ethoxy-compound (11) led us to claimed initially to yield perfiuoro-2-azetine (I), but the suspect that the azetine had been mi~-identified.~ assertion that the azetine reacted with ethanol to give Subsequently, 495 perfluoropropenyl azide was shown to

R. E. Banks, W. M. Cheng, and R. N. Haszeldine, J . Chem. Part XVI, R. E. Banks, D. S. Field, and R. N. Haszeldine, Soc,, 1962, 3407.

C. S. Cleaver and C. G. Krespan, J . Amer. Chewt. SOC., 1965, I. L. Knunyants and E. G. Bykhovskaya, Doklady Akad. 87, 3716.

R. E. Banks and G. J. Moore, J . Chem. SOC. ( C ) , 1966, 2304.

Science and Technology, Manchester M60 1 QD

J . Chem. SOC. ( C ) , 1969, 1866.

Nauk S.S.S.R,, 1960, 131, 1338.

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Org. 2599 decompose into nitrogen and perfluoro-(2-methyl-2H- azirine) (111) , not perfluoro-2-azetine, and the reaction of the azirine with ethanol has now been investigated.

EC

A rapid, exothermic reaction occurred when perfluoro- (2-methyl-2H-azirine) was treated with an excess of ethanol a t room temperature, and the product isolated was identified as ethyl 2-ethoxy-3,3,3-trifluoro-2- hydroxypropionate (IV) containing ca. 10% of ethyl 3,3,3- trifluor0-2~2-dihydroxypropionate (V). Thus the azirine, like other perfluoro-imine~,~~~ readily suffers nucleophilic attack by ethanol a t the N X bond, and a possible route to the propionates (IV) and (V) is shown below ( c j . ref. 3, 6, and 7) . Water 8 and methanol are known to add rapidly across the keto-group in a trifluoropyruvic ester, e.g. , (VI).

Hydrolysis of perfluoro- (2-methyl-2H-azirine) yields trifluoropyruvic acidJ5 isolated now as its monohydrate, 3,3,3-trifluoro-2 ,2-dihydroxypropionic acid, which gave a mixture of ethyl 3,3,3-trifluoro-2,2-dihydroxy- and 2- ethoxy-3,3,3-trifluoro-2-hydroxy-propionate when heated with ethanol and a trace of concentrated hydrochloric acid. Like other derivatives of trifluoropyruvic acidJ5 these esters and the monohydrate undergo the haloform reaction and yield fluoroform when treated with aqueous sodium hydroxide. Carbon monoxide , carbon dioxide ,

CkFC- CF; FC-

E4 F+ E $0 +H20 i i I H

c~*c*cC??Et . CF,=CF*C02Et CF,.FC-C(OH)*OEt - I iii \N/

II L

NH N% H iii

CF,. C (OH 1 (0 E t 1 C%E t ( I V I

C FJ C tOH);CO&t (V1

-<: I C % C 0- C 9 E t

(VI1

Reagents: i, EtOH; ii, H,O; iii, H+,H,O; iv, -HF.

and a trace of material believed to be trifluoropyruvic acid were obtained when 3,3,3-trifluoro-2,2-dihydroxy- propionic acid was heated with phosphorus pentoxide at 150"; unsuccessful attempts to dehydrate the

See, for example, D. A. Barr, and R. N. Waszeldine, J . Chew. SOC., 1956, 3428 and R. E. Banks and E. D. Burling, J . Chew. Soc., 1965, 6077.

D. A. Barr and R. N. Haszeldine, J . Chem. Soc., 1955, 1881. * I. L. Knunyants, V. V. Shokina, and V. V. Tyuleneva,

Doklady Akad. Nauk S.S.S.R., 1966, 169, 594. 4x

dihydroxy-acid with phosphorus pentoxide or thionyl chloride have been reported.1°

EXPERIMENTAL

1.r. spectra were measured with Perkin-Elmer spectro- photometers, models 21, 137, and 257, and n.m.r. spectra with a Perkin-Elmer instrument model R10 operating at 56-46 (19F) and 60 MHz (IH). Molecular weights were determined by Regnault's method.

Reactiows of Perfluoro- (2-methyZ-2H-azivine) .-(a) Hydro- lysis. The azirine (14.05 g., 96.90 mmoles), prepared as described previouslyJ5 and water (100 ml.) were kept in a 300-ml. Pyrex ampoule for 6 days a t room temperature. The product was extracted with ether (3 x 200 ml.) and the extract was evaporated under reduced pressure. The yellowish residue was sublimed in vacuo to give (bath temp. looo) 3,3,3-trifluoro-2,2-dihydroxypropionic acid (6.99 g., 43.7 mmoles, 45%) (Found: C, 22.8; H, 2.1. Calc. for C3H3F304: C, 22.5; H, lag%), a white hygroscopic solid, n1.p. 122" (sealed tube) (lit., 118-5-119,10 122-125,11 and 124--126" Am=. (mull) 2.88, 2.97, 3*02sh, 3-13 (OH str.), 5*75sh, 5-93sh, 5.96, 6.17 pm (C:O str.), 8~ (20% soln. in acetone) - 0.33 and + 0-65 p.p.m. (interchange benzene; relative intensity 1 : 2), SF 3-6.3 p.p.m. (interchange trifluoroacetic acid; phase as for lH), and (bath 170") an unidentified hygroscopic yellow solid (1.12 g.) (Found : C, 25.6; H, 1.5; F, 38.2; N, 7.0. Calc. for C,H,F,NO,: C, 25.4; H, 1.6; F, 40.2; N, 7.4%), m.p. 184" (decomp.), that showed i.r. absorptions typical of a carboxylic acid [3-13 (broad; bonded O-H str.) and 5-76 pm (C:O str.)] and dissolved readily in 2~-sodium hydroxide with the liberation of fluoroform (identified by i.r. spectroscopy).

An exothermic reaction occurred when the azirine (4.0 g., 28 mmoles) was passed into absolute ethanol (50 nil.) a t room temperature. Distillation of the product afforded ammonium fluoride (0.17 g.) and a sweet- smelling liquid (2-7 g.) (Found: C, 36.0; H, 5 ~ 3 % ) ~ b.p. 90"/130 mm., A,,, (film) 2.88 (OH str.), 3.34, 3.40, 3-44 (CH str.), 5.74 pm (C:O str.), which was shown by n.m.r. spectroscopy to be a 13 : 1 molar mixture of ethyl 2-ethoxy- 3,3,3-trifluoro-2-hydroxypropionate (Calc. for C,H,,F,O, : C, 38.9 ; H, 5.1 yo) and ethyl 3,3,3-trifluoro-2,2-dihydroxy- propionate (Calc. for C5H,F,04: C, 31.9; H, 3.7%). The 19F spectrum of the mixture showed two singlets of relative intensity 13 : 1 a t 4.0 and 5.6 p.p.m. [cf. CF,*C(OH),CO,H, 6.3 p.p.rn.1 to high field of trifluoroacetic acid (interchange), and the lH spectrum was essentially that of ethyl 2-ethoxy- 3,3,3-trifluoro-2-hydroxypropionate, showing four band absorption systems of approximate relative intensities 1 : 2 : 2 : 6 at 1.4br (s, C-OH), 2.5 (4, CO,-CH,*CH,), 3.1 (m, C*OCH,*CH,), and 5-6 (m, both types of C H , ) to high field of benzene (interchange).

The 13 : 1 molar mixture of ethyl 2-ethoxy-3,3,3-trifluoro- 2-hydroxy- and 3,3,3-trifluoro-2,2-dihydroxy-propionate (0-500 g.) was heated with 2~-sodiuni hydroxide (20 ml.) in a 50-ml. Pyrex ampoule at 100' for 1 hr. The volatile product (0.165 g., 2.357 mmoles) (Found: ill, 70. Calc. for CHF,: M , 70) was dried (P205) and shown by i.r. spectroscopy to be fluoroform. The hydrolysate gave a positive test for fluoride ions. Assuming that the starting

Neth. Appl. 6,611,522/1966; Clzem. Abs., 1967, 66, 115,323n. lo D. Sianesi, A. Pasetti, and F. Tarli, J . Org. Chew., 1966, 31,

11 S. Selman, U.S.P. 3,321,517/1967; B.P. 1,051,650/1966.

@) Etlzanolysis.

2312.

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2600 J. Chem. SOC. (C), 1969 material was pure ethyl 2-ethoxy-3,3,3-trifluoro-2-hydroxy- propionate, the yield of fluoroform was 102y0, which is consistent with the presence of the 2,2-dihydroxypropionate.

Reactions of 3,3,3-T~ifEuoro-2,2-dihydroxypro~ionic Acid. -(a) Hydrolysis. The acid (0-1642 g., 1.024 mmoles) was dissolved, in 'uacuo, in 2~-sodium hydroxide (100 ml.) in a 1-1. Pyrex bulb. The solution was kept at room temper- ature for 5 days, then the volatile product was dried (P,O,) and shown by i.r. spectroscopy to be fluoroform (0.067 g., 0-957 mmoles, 94%) (Found: M , 69. Calc. for CHF,: M , 70). The yield of oxalic acid, determined by titration of the neutralised hydrolysate against potassium perman- ganate, was 95%.

(b) With ethanol. 3,3,3-Trifluoro-2, 2-dihydroxypropionic acid (5.07 g., 31.7 mmoles) was heated under reflux with absolute ethanol (1.74 g. , 37.8 mmoles) containing a trace of concentrated hydrochloric acid. The product was dried (MgSO,) and distilled to give a liquid (1.10 g.) (Found: C, 32.15; H, 4.0%), b.p. 46*/18 mm., A,,,, (film) 2.9br (bonded OH), 3.34, 3-38, 3-44 (CH str.), 5-73 pm (C : 0 str.), which was shown by g.1.c. (2 m. silicone oil-Celite, 110") and I@F n.m.r. spectroscopy to be a ca. 70 : 30 molar mixture of ethyl 3,3,3-trifluoro-2, Z-dihydroxy- and 2-ethoxy-3,3,3-tri- fluoro-2-hydroxy-propionate. The 19F n.m.r. spectrum of the mixture showed two singlets of relative intensity 7 : 17 a t 3-97 [CF,*C(OH) (OEt)*CO,Et} and 5-58 p.p.m. [CF,* C(OH),-CO,Et] to high field of trifluoroacetic acid (inter- change). The lH spectrum of the mixture showed three

major absorption band systems of approximate relative intensities 2 : 2 : 3 a t 1.3 [s, C(OH),], 2.3 [q, C(OH)z*CO,* CH,*CH,], and 5-4 p.p.m. [t, C(OH),*CO,*CH,*CH,] to high field of benzene (interchange); a minor absorption centred a t 3.1 p.p.m. assigned to the methylene protons of the 2-ethoxy-group of the 2-ethoxypropionate was clearly displayed, but the other absorptions assigned to this ester (2 -5 and 5.6 p.p.m.; see above) were masked by the more intense bands assigned to the ethoxycarbonyl group of the 2,2-dihydroxy-compound.

An intimate mixture of 3,3, S-trifluoro- 2,Z-dihydroxypropionic acid (0.424 g., 2-65 mmoles) and phosphorus pentoxide (0.7 g.) was heated a t 150" for 1 hr. in a 25-ml. Pyrex ampoule. The volatile product was fractionated to give carbon monoxide (0.47 mmole, 18% of 1 mol.) (Found: M , 29. Calc. for CO: M , 28) with a correct i.r. spectrum, carbon dioxide (0.72 mmole, 27% of 1 mol.) (Found: M , 44. Calc. for CO,: M , 44) with a correct i.r. spectrum, and a material believed to be trifluoro- pyruvic acid (0.04 mmole, 1.5%) (Found: M , 139. C,HF303 requires M , l42), Amax. (vapour) 2 . 8 3 ~ (nonbonded OH str.), 3.24m, 3-43m (broad, bonded OH str.), 5.50m-s (C : 0 str.), 5.61s (C : 0 str.), 7.81m, 8.05vs, 8*32vs, 8.44vs, 8-33, 8.91s (d, C-F str.), and 14.00m pm (CF, def.).

D. B. and G. J. M. thank the S.R.C. and the D.S.I.R., respectively, for Studentships.

[9/870 Received, May 23rd, 19691

(c) Dehydration.

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