Feb. 20, 1955
DIELS-ALDERREACTIONS WITH FLUORINE-CONTAINIKG OLEFINS [CONTRIBUTION PROM THE
DEPARTMENT OF CHEMISlRY
915
OF PURDUE UNIVERSITY]
Diels-Alder Reactions with Fluorine-containing Olefins BY E. T. MCBEE,C. G. Hsu,’ 0. R. PIERCE AND C. W. ROBERTS RECEIVED JULY 21, 1954 The Diels-Alder reactions of five fluorine-containing dienophiles with cyclopentadiene, butadiene and anthracene have been investigated. 4 n adduct was obtained in all cases except in the reaction between allyl fluoride and butadiene. Qualitatively, the relative order of reactivity was found to be: CF&F=CF2 > C?F&H=CHZ > CFaCH=CHz > C H t F C H = C H z > CFaC( CHa)=CH2.
adducts in 84-98% yield. 2-Methyl-3,3,3-trifluoroDiscussion The Diels-Alder reactions of allyl chloride and propene can be added to anthracene a t 200’ in bromide,2 vinyl chloride, 1,2-dichloroethylene and 57% yield. The adducts A from 3,3,3-trifluoropropene, 3,3,trichloroethylenea have been carried out with cyclopentadiene. More recently it has been shown 4,4,4-pentafluoro-l-buteneand 2-methyl-3,3,3-trithat 1,2-dibromoethylene and 1,3-dichloropropene fluoropropene with cyclopentadiene were accomcan be used as dienophiles4; cis- and trans-dichloro- panied by small amounts of bis-adducts, assumed to ethylene have been condensed with a n t h r a ~ e n e . ~have the structure B. Unsubstituted olefins, e.g., ethylene and propylene react with cyclopentadiene and cyclohexadiene a t high temperature and under pressure.6 I n view of the polarization of the double bond by the strong electron-withdrawing effect of fluorine A B C atoms,’ fluorine-containing olefins should be exR = H,C F z , C,Fb; R’ =: H , CH, pected to act as dienophiles regardless of whether the reaction proceeds by an ionic mechanisms or The adducts, A and C from cyclopentadiene and involves a n intermediate molecular complex. butadiene, respectively, were converted to diIn order to determine the influence of fluorine bromides by means of bromine in carbon tetraatoms in dienophiles, allyl fluoride, 3,3,3-trifluoro- chloride for identification purposes. The olefins propene, perfluoropropene, 3,3,4,4,4-pentafluoro-l-were regenerated by debromination with zinc and butene and 2-methyl-3,3,3-trifluoropropenewere ethanol. This procedure was utilized also to treated with butadiene, cyclopentadiene and an- separate 4-pentaff uoroethylcyclohexene and 4thracene. Each of the fluorine-containing olefins methyl-4-trifluoromethylcyclohexenefrom the acreacts with cyclopentadiene at 135 and a t 190’. companying butadiene dimer, vinylcyclohexene. Under comparable conditions, the yields of adducts The structures of the adducts A are further were similar and in the range of 60-7070, except supported by the infrared absorption spectra which with allyl fluoride (27%) and 2-methyl-3,3,3- contain characteristic bands a t 7.14-10.0 p (C-F), trifluoropropene (25%). I n the case of allyl 5.97-6.11 1.1 (CH=CH), 3.23-3.5 p (C-H)’O and a fluoride, the single fluorine atom probably exerts strong band a t 13.8-14.0 p, observed in bicycloinsufficient polarization on the double bond, while [2.2.1Iheptenes such as bornylene, l1 norbornylene, the reactivity of 2-methyl-3,3,3-trifluoropropene dehydronorborneol, 5-carboxylbicyclo [2.2.1]-2-hepmay be reduced both by polar and steric effects. tene, 5-chlorobicyclo[2.2.1]-2-heptene and 5-bromoThe results obtained with butadiene are similar to bicyclo [2.2.1]-2-heptene.12 The infrared spectra of those with cyclopentadiene. Peduoropropene the dibromides from the adducts C have two bands gave the highest yield, 2-methyl-3,3,3-trifluoro- a t 9.95-10.53 p and 9.47-10.00 p which are charpropene the lowest ( 15y0), while allyl fluoride failed acteristic of cyclohexane derivatives. la to give an adduct under the conditions employed. The anthracene adducts have been established The reactions of the olefins with anthracene as 9,lO-adducts by means of their ultraviolet show more pronounced temperature effects. Allyl absorption s p e ~ t r a ~ ~ all- ~the ~ * compounds exfluoride and perfluoropropene gave adducts a t 110’ ; hibited three maxima i t 252, 264 and 272 mp with 3,3,3-trifluoropropene, perfluoropropene and 33,- log E’S of 3.0-4.0. 4,4,4-pentafluoro-l-butenereact a t 200’ to give Experimentall6 (1) This paper represents part of a thesis submitted by C. G. Hsu t o the Graduate School, Purdue University, in partial fulfillment for the degree of Doctor of Philosophy. (2) K. Alder and E. Windemuth, Bcr., 71, 1939 (1938). (3) K. Alder and H. F. Rickert, Ann., 649, 1 (1939). (4) E. T. McBee, R . K. Myers and H. Rakoff, THISJOURNAL, 77, in press (1955). (5) S.J. Cristol and N . H. Hause, ibid., 74, 2193 (1952). (6) 0.Calingaert. H . Soroos and H. Shapiro, I n d . Eng. Chcm., 86,
1055 (1944). (7) A. L. Henne and J. Kaye, ibid., 71, 3369 (1950). (8) M. J. S. Dewar, “Electronic Theory of Organic Chemistry,” Oxford University Press, London, Great Britain, 1949, pp. 153, 184. (9) A. E. Remick, “Electronic Interpretations of Organic Chemistry,” 2nd Ed.,John Wiley and Sons, Inc., N e w York. N. Y.,1949,I). 477.
Preparation of the Olefins. Allyl Fluoride.-Allyl
fluoride,
b .p. -3’, was prepared in 30% yield from allyl bromide and (10) H. Gilman, “Organic Chemistry,” Vol. 3,John Wiley and Sons Inc., New York, N . Y., 1953. pp. 143-151. (11) G.S w a m and F. J. Cripwell, I n d . Chemist, 24, 573 (1948). (12) J. D.Roberts, el al., THISJOURNAL, 72, 3316 (1950). (13) L. Pi. Marrison, J . Chem. SOL, 1614 (1951); (14) E.Clar, Ber., 86,503 (1932). (15) D.D. Phillips and J Cason, THISJOURNAL, 74, 2934 (1952). (16) All temperatures are uncorrected; the melting points were determined with a Fisher-Johns melting point apparatus. Carbon, hydrogen and bromine analyses by H. Galbraith, Knoxville, Tenn , and Mrs. C. S T. Yeh of this Deoartment. Fluorine analvses bv. Clark Microanalytical Laboratory, University of Illinois, Urbana, I11
E. T. MCBEE,C. G. Hsu, 0. R. PIERCE AND C. W. ROBERTS
916
VOl. 77
TABLE I CYCLOPENTADIENE ADDUCTS Compound
Ratio CsHs Olefin
From olefin
I I1
Temp., Time, OC. hr.
Yield, %b
B.p., OC.
Carbon, % Calcd. Found
n%
Hydrogen, % Calcd. Found
Fluorine, % Calcd. Found
CFHzCH=CHz CF3CH=CHz
1 . 0 135" 60 27 66' 1.4548 76.19 76.13 8 . 7 3 8.78 15.08 15.82 1 . 0 135 60 65 119 1.4051 59.25 59.17 5.56 5.50 35.19 34.87 0 . 8 190 24 57c I11 CzSCH=CHz 1 . 0 135 60 66 130 1.3853 50.99 51.17 4.25 4.36 44.76 44.59 0 . 8 190 24 60d I\* CFaCF=CFz 1 . 0 135 60 69 141 1.3741 44.44 44.48 2 . 7 8 2.87 52.78 52.38 0 . 8 190 24 66 V CFsC(CH3)=CHz 1 . 0 135 60 22 136 1.4168 61.36 31.58 6.25 6.24 32.40 32.22 0 . 8 170 168 23 A ZY6 yield of bis-adduct was Allyl fluoride is unstable a t higher temperatures. Yield based on unrecovered olefin. obtained, b.p. 95-96' (10 mm.), n% 1.4733. :Inn/. Calcd. for Cl3H1&: C, 68.60; H, 6.16. Found: C, 69.06; H, 5.76. C, 59.60; H, 5.38. A 4% yieldof bis-adduct was obtained, b.p. 99-100" (10 mm.), TZ% 1.4488. '4naZ. Calcd. for CI~HILF.,: Pound: C, 59.65; H , 5.58. e A 7% yield of bis-adduct was obtained, m.p. 66.5'. Anal. Calcd. for C ~ ~ H I T F C,I :69.30; H. 7.01. Found: C, 69.18; H, 7.19. ' A t 55mm. (i
TABLE I1 BUTADIENE ADDUCTS'I Compounds
From olefin
Yield,
B.P.,
%b
O C .
Carbon, % Calcd. Found
ilzaD
Hydrogen, 92 Calcd. Found
6.00 1.3856 56.00 56.01 CFaCH=CHz 35 104 4.50 38 119" 1.3725 48.00 47.80 CzF5CH=CHz CF3CF=CFz 64 97 1.3430 41.18 41.39 2.94 CF3C(CHa)=CHz 15 122 1.3989 58.54 58.57' 6.71 a The reactioris were carried out by heating for 21 hours a t 180" with a molar ratio of 0.9 for based on unrecovered olefin. C The pure product was obtained free of vinylcyclohexane dibromo compound. IrI VI1 VI11 IX
Fluorine, ? '& Calcd. Found
38.00 37.54 6.20 47.50 45.22 4.71 2.94 55.88 56.05 6.82 34.76 33.43 Yield butadiene and olefin. by debrominating the purified
TABLEI11 ANTHRACENE ADDUCTS Ratio
CuHia Olefin
Olefin
0.21 .47 .41 .75 .75 .32 CFaC(CHa)=CHz .28 .75 a Yield based on unrecoverxi
CFHzCH=CH1 CFsCH=CHz CzFsCH-CHz CFaCF=CFz
Temp., Time,
"C.
110 200 200 110 150 200 200 110
hr.
24 20 20 24 24 20 20 24 anthracene.
Carbon, % Found Calcd.
Hydrogen, % Found Calcd.
Fluorine, % Calcd. Found
Yield,
M.P., OC.
75 83 86 76 95 97 56
