COMMUNICATIONS TO THE EDITOR
3912
Vol. 83
of substitut.ed cycloheptai~es~ observed in per- azoisobutyroiiitrilc, azoisobutane, and hexaphtnylhydrctazulenes.R The application of this rearrange- ethane also reacted with N2F4 to produce the corriieiit to the svnthesis of seven-menibered aromatic responding difluoratniii~s, I , b.p. 71-72' (1 50 mni ), coiiii)ounds is now ill progress. 11,b.p. 54-53'and H I , 1i1.p.81-82' We are irictc1)ted to Prof. F. Sondheirner for his (CHa)?C--NF? ( C M T ) ~ C N F ~ (C611G)jC XI'? interest and eiicourageinent, and to Syntex S.A., , Mexico, for a generous gift of starting materials, CN and optical rotatory dispersion measurements. I I1 Ill (7) H . J . I?. 1,newenthal atid R . Kona, J . Chcin. Soc , 1429 (1961),
Satisfactory analyses were obtained for a11 these compounds. Their F19 n.ni.r. spectra6 all show (IQGl). signals from the NF, groups a t -44724, -4224, and - 4430 c.P.s., respectively. These compounds resist T H E DANIEL SIISI'I~ J l E S E A R C H INSTITUTE T H E b ' E I Z M A N N 1XSTITCTE OF S C I E N C E Y E H U D A MAZUR hydrolysis. I i ~ r r o v o r r r ,ISRAEL MANASSE NUSSIM N,N-Difluoramides also may be obtained by the RECEIVED J u L y 10, 1961 reaction of aldehydes with NzF4. N,N-Difluoroacetamide and difluoramine were produced when acetaldehyde arid N2F4 were heated a t 150' in a Pyrex TETRAFLUOROHYDRAZINE : A VERSATILE INTERMEDIATE FOR THE SYNTHESIS OF N-FLUOR0 bulb. This reaction may be compared to the conCOMPOUNDS version of benzaldehyde to benzoyl chloride by Sir: chlorine.' We have found tetrafluorohydrazine,' NzF4, to be 150' CHaCMO f NnFd ----+ CHjCONFz + HNF, a versatile intermediate for the synthesis of both IV organic and inorganic compounds containing the difluoramino group, NF2. N2F4participates in a NzF4 must be handled cautiously. Oxygen must variety of free radical reactions as might be ex- be excluded rigorously from mixtures of N2F4 and pected from its low N-N bond strength.2 organic compounds or explosions are likely to result. NzF4 and chlorine react under the influence of The difluorarnino compounds themselves should ultraviolet light in Pyrex to produce chlorodifluor- also be handled with care. ClNF2. This is an equilibrium reaction in Acknowledgment.-This work was conducted which the formation of chlorodifluoramine is under Army Ordnance Contract DA-01-021 ORDfavored by a large excess of chlorine and a relatively 5135. The support and encouragement of Dr. high temperature (80'). The synthesis of difluor- Warren D. Niederhauser is gratefully acknowlamine, HNF2, by the hydrogen abstraction reacedged. tion between NzF4 and thiophenol has been re(7) C. Walling, "Free Radicals in Solution," John Wiley and Sons, p~rted.~ The photolysis of diketones in the presence of Inc., New York, N. Y . , 1957, p. 369. ROBERTC PETRY AND I l A A S COMPANY NzF4 a t room temperature in Pyrex caused the ROHM KEDSTONE ARSENALR E S E A R C H D I V I S I O N formation of N,N-difluoroamides in good yield. JEREMIAH P. FREEMAN FT IJNTSVII,LE, ALABAMA and refs. cited therein.
(8) N I,, Allinfier and V . B . Zalkow, J . A m . C h e m . hoc., 83, 1144
00
1/11
RCCH
RECEIVEI) J I J N E 26, 1961 IlW __f
N2F4
HCC>Xl'?
-
._
.
~-
CARBONIUM ION SALTS. 11. REACTION OF
WITH INORGANIC HALIDES ; The reaction has beeti applied successfully to biace- CYCLOHEPTATRIENE TROPENIUM CHLOROBORATE' tyl, glyoxal and benzil. For example, 0.06 mole of There is much interest in compounds of the chlobiacetyl and 0.06 mole of NzF4irradiated for sixteeii hours with a Hanovia EH-4 lamp yielded 0.077 roborate anion2a-i; however, their preparation has required high temperature and pressure,2d long mole of N,N-difluoroacetamide (IV), b.p. 45-47'; yield 80% based on N2F4consumed. -4nal. Calcd. milling of solids,2hor liquid hydrogen chloride solFound; N , 14.40. vent,2g and the products often give unsatisfactory for C2H3F2NO: N, 14.74. The material was characterized by its infrared analyses. The only easily prepared, stoichiometric spectrum (yc-0 1820 cm.-l>, n.1n.r. spectrums (FL9 chloroborate reported is cesium chloroborate. 2 i . 3 We find that the reaction of boron chloride with resonance a t -4270 C.P.S. and H' resonance a t 4in methylene chloride (dry condi190 c.P.s.), and by its solvolysis in ethanol to ethyl ~ycloheptatriene~ tions under nitrogen, room temp. for 24 hr., mole acetate and difluoramine. Alkyl radicals6 generated by the decomposition of ratio BCl3/C7Hs of 1.4/1) gives 12.6% tropenium (1) C. B . Colburn and A . Kennedy, J . A m . Chem. Sac., 80, 5004 (19i58). (2) C. B. Colburn and F.. A . Johnson, J . Chem. P h y s . , 33, 1869 (I9GO). (3) R . C . Petry, J . A m . Chem. Soc., 82, 2400 (1900). (4) J . P. Freeman, A. Kennedy and C. B . Colburn. i b i d . , 82, 8304 (1960). (5) Flu resonauces are recorded in cycles from external CFsCOiH and HI resonances from external C&a. Negative values indicate
resonance at lower field than the standard. 16) The photochemical reaction between alkyl iodides and NaF, prestimably involves alkyl radicals; J. W. Frazer, J . Inorg. X f l c ! . C h v ! w , , 16, 6 3 ( l ! X O ) .
(1) Supported by the Petroleum Research Fund, Grant 443-A. (2) (a) D. R. Martin, Chem. Rcu.. 42, 581 (1948); (b) N. N.Greenwood and K . Wade, J . Chem. Sac., 1527 (1956); (c) M. F. Lappert, Proc. Chem. SOC.,121 (1957); (d) E. L. Muetterties, J . A m Chem. S O C . , 79. 65fi3 (1957); (e) A. B. Burg and E. R. Birnbaum, J . Inarg. N d . Chem., 7 , 146 (1958); (f) D. E . Burge, H. Freund and T. H. Norris, J . P h y s . C h e m . , 63, 1969 (1959); ( 6 ) T. C. Waddington and F. Klanberg, N o l u r v i s s , 20, 678 (1959); J . Chem. SOC.,2329, 2332 (1960); (b) W. Kynastron, B . E. Larcombe and H. S. Turner, ;bid., 1772 (1960); (i) E. L. Muetterties, J . Inarg. Nucl. Chem.. 12, 355 (lg60). (3) LappertZ0 has reported the preparation of pyridinium chloroborate but does not give experimental or analytical details. (4) Generoilsly supplied by the Shell Chemical Company.
Sept. 20, 19G1
COMMUNICATIONS TO THE EDITOR
chloroborate as white needles, n1.p. 11Y--12Oo,ultraviolet spectrum (96% sulfuric acid)6: Xmax 268 (shoulder), 273.5 (4350), 280 m p ; 37.4y0 tropenium ion; calcd. for C7H7BC14: 37.38y0 tropeniuin ion. z,lnal.s Calcd. for CvH7BC14: B, 4.44; c1, 58.19; neut. equiv., 48.76. Found: B, 4.19, 4.25; C1, 58.33, 55.33; neut. equiv., 48.99,49.20. Reaction in cyclohexane (identical conditions) gives 6.0% tropenium chloroborate of 94.5y0 purity and 78.5% recovered cycloheptatriene. Reaction without solvent gives 16.1Y0tropenium ion and much polymer. Reaction in methylene chloride with t-butyl chloride co-catalyst (equimolar amount) gives 25.2% tropenium chloroborate of high purity. Tropenium chloride with boron chloride gas in methylene chloride gives 34.070 tropenium chloroborate as white needles with slight enrichment of the chloride; founds: B, 4.40; C1, 57.32; neut. equiv., 49.48; 38y0tropenium ion. Tropenium chloroborate (colorless single needles) is slightly hygroscopic; it dissolves slowly in water to give solutions of tropenium ion (Amax 275 mp (4270))' and boric acid. I t sublimes to give unchanged chloroborate (major) and tropenium chloride (minor) in contrast to the bromoborate6 which gives only the bromide. Wiberg8 reports a 1: 1 complex of boron chloride and triphenylmethyl chloride (correct analysis, no m.p. below 200'); though not so identified, this was the first ionic chloroborate prepared. We find that boron chloride and triphenylmethyl chloride in methylene chloride give 78.8% triphenylcarbonium chloroborate, precipitated as yellow microcrystals by cyclohexane, visible spectrum (96Y0 sulfuric acid) :6 Xmax 405, 432 mM (38,200) ; 61.1% triphenylcarbonium ion; calcd. for C19H16BC14: 61.44%. Anal. Calcd. for Cl~Hl~BC14: B, 2.73; C1, 35.85; (CsH6)aCOH,65.74. Found5 B, 2.40; C1, 34.86; (CsH6),cOH, 65.80 (n1.p. 162' (reported:9 1622.5'). This compound reacts instantly with cycloheptatriene in methylene chloride to give 100% tropenium chloroborate and 86.6% triphenylmethane. This rapid hydride exchange indicatessJs10 that triphenylcarbonium chloroborate is an ionic salt and contains a BC14- entity that can be transferred intact in a chemical reaction. Conversion of cycloheptatriene (TrH) to tropenium ( T r f ) by metal halide with no co-catalyst may involve addition (1) followed by hydride transfer, or direct hydride abstraction (2). With cocatalyst (A = R-, H-; B = -OH, -X) route (3) or (4) may be followed.ll In dry cyclohexane virtually no reaction occurs between cycloheptatriene and boron fluoride (0.55% tropenium formed) l2 (5) H. J. Dauben, Jr., F. A. Gadecki, K. M . Harmon and D . L. Pearson, J . A n t . Chcm. Soc., 79, 4557 (19.57). (6) For methods of spectral and chemical analysis see K . M . Harmon and A. B. Harmon, ibid., 83, 865 (1961). (7) W. von E. Doering and L. H. Knox, ibid., 76, 3203 (1854). ( 8 ) E. Wiberg and U . Heubaum, Z . anorg. allgem. C h e m . , 222, 98 (193.5). (9) Hg. Frey, E'er., 18, 2517 (1895). (10) (a) H . J. Dauben, Jr., and D. L. Pearson, Abstracts, 126th Meeting. American Chemical Society, New York, N . Y.,Sept. 13, 1954. p. 18-0; (b) D. L. Pearson, P h . D . Thesis, Universityof Washingtou, 1955. (11) H . J. Dauben, Jr., K. M. Harmon, A. B. Harmon and L. K. Honnen. J . A m . Chem. SOC., in preparation, will discuss these reactions and mechanistic paths in detail,
TrH
MXn
391.3
+ MXtl + Tr+ + HMX, + A-B- BMX, + A' A
TrH
+
A'
----
T r '
(2)
A
+
AH
(4)
and stannic chloride (O.O86yO tropenium formed) in agreement with the failure of these halides to cause cationic polymerization without cocatalysts.l a Stannic chloride in dry methylene chloride gives 16.1% tropenium chlorostannate (white cubes from 12 N HCl, m.p. 252' (reported," 252')). Water, hydrogen chloride, and t-butyl chloride14 increase the yield ; however, in their absence methylene chloride must function as co-catalyst by reacting with stannic chloride to give a cationic species (not necessarily a free carbonium ion) which attacks cycloheptatriene. Stannic chloride and trianisylmethane in dry methylene chloride give only 0.3570 trianisylcarbonium ion (Amax 485 m p in ,570 sulfuric acid)16 in 18 days. As trianisylmethane readily yields a stable cation through hydride loss, l6 the cationic species derived from stannic chloride and methylene chloride fails to abstract hydride, and must attack cycloheptatriene by route (3) and not (4). Boron chloride converts trianisylmethane to the cation in cyclohexane (24.7y0) and methylene chloride (8.5y0), and thus-like boron bromides," appears able to abstract hydride from an organic hydride donor. Methylene chloride appears to act as a co-catalyst in the cycloheptatriene-boron chloride reaction (presumably by route (3)) but this solvent hinders reaction with trianisylmethane where additive co-catalysis cannot be effective. This effect is most likely due to greater solvation (relative to cyclohexane) of boron chloride by methylene chloride. Joy and Lappertls report that boron chloride and cycloheptatriene give benzylboron dichloride. We find traces of aromatic material but have not iso(12) D. N. Kursanov and M. E. Vol'pin. Doklady A k a d . Nottk, S . S . S , R . , 113, 339 (1957); C . A , , 81, 14572f(1957), report tropenium ion formation and extensive polymerization when cycloheptatriene was heated with boron fluoride etherate; they attribute this to a reaction like (2) above. We feel their observations were cawed by water co-catalyst since we observe no polymerization (quantitative recovery of cycloheptatriene) with BFa gas in dry cyclohexane; heating may have caused some polymerization in their case but this is doubtful in ether. (13) (a) A. G. Evans and G.W. Meadows, T Y Q ~ Faraday ~ . Soc., 46, 377 (1950); (b) R . 0. Colclough and F. S. Dainton, ibid., 64, 886
(1958). (14) D. Bryce-Smith and N. A. Perkins, Chemistry and I n d u s t r y . 1022 (1959). (15) N . C. Deno, J. J. Jarurelski and A. Schriesheim, J . A m . Chem. S O C .77, , 3044 (1955). (16) L. L. McDonough, Ph.D. Thesis, University of Washington, 1960. (17) K. M . Harmon and K . D. Stevens, unpublished work; boron bromide in dry methylene chloride converts trianisylmethane to the cation in 77.5% yield in two days. ( 1 R ) F. Joy and h l . F. Lappert, P m c . C h r m . .So950/0. There were characterized by melting point or in the case of is no apparent solvent effect upon the equilibrium new compounds by elemental analysis. Financial (CDC13, C6He, pyridine). support from the National Science Foundation is These results, together with corroborative in- acknowledged. frared studies on the above and related compounds,2 (3) L. W. Reeve% Con. J . Chcm., 96, 1351 (1957). offer further evidence of the greater stability of the (4) A. Burawoy and A . R . Thompson, J . Chcm. SOC.,1443 (1963) (5) E. Sawicki, J . Org. Chem., 99, 743 (1957). ketamine form in aliphatic compounds as compared ( 8 ) K . J. Morgan, J . Chcm. SOC.,2151 (l96l), and references therein. to either the ketimine or enol-imine tautomers. OF CHEMISTRY Accordingly, a search was made for other systems in DEPARTMENT UNIVERSITY G. 0. DUDEK which an alternate tautomer would be of compa- HARVARD R. H. HOLM CAMBRIDGE 38, MASS. rable stability, RECEIVED AUGUST16, 1961 Derivatives of o-hydroxynaphthones were investigated. The tautomers JI and 111 are possible STRUCTURE OF a-LUMICOLCHICINE-SOME for the base derived from I-hydroxy-2-naplithone THE EXAMPLES OF DIAMAGNETIC SHIELDING BY THE and a monoamine. CARBON-OXYGEN DOUBLE BOND (1) G. 0. Dudek and R. H . Holm, J . A m . Chcm. SOC.,88, 2089 Sir: (1981). a-Lumicolchicine, which is formed with 8(2) N. H. Cromwell, F. A. Miller, A. R. Johnson, R. L. Frank and D. J. Wallace, {bid., T i , 3387 (1949). lumicolchicine and y-lurnicolchicine in the irradia(10) American Chemical Society-Petroleum Research Fund Scholar, 1900.
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