NOVEMBER, 1964
NOTES
The di-Grignard thus prepared was allowed to react with phenyldichlorophosphine to yield the desired cyclic 5,lO-dihydrophenophosphazine in only 14.2% crude yield. Experimental All reactions involving organometallic intermediates were carried out under an atmosphere of dry, oxygen-free nitrogen. Melting points are uncorrected. 2,2'-Dichlorodiphenylamine.-This compound was prepared by the same procedureS outlined for the synthesis of 2,2'-dibromodiphenylamine. The physical properties and yields of the intermediates isolated are: N-o-chlorophenylbenzimidoyl chloride, b.p. 146" (0.5 mm.), 75%; o-chlorophenyl N-o-chlorophenylbenzimidoate, m.p. 67.5-68.5", 59%,; N-benzoyl-2,2'-dichlorodiphenylamine, m.p. 152-153', 827,; 2,2'-dichlorodiphenylamine,m.p. 83.5-84", 897,. N-Methyl-2,2'-dichlorodiphenylamine.-A solution of 2,2'dichlorodiphenylamine (2.4 g., 0.01 mole) in 10 ml. of tetrahydrofuran was added dropwise to a mixture of sodium hydride (0.24 g., 0.01 mole, 50% in mineral oil) and methyl iodide (1.4 g., 0.01 mole) in 10 ml. of tetrahydrofuran maintained under a dry nitrogen atmosphere. The only evidence of reaction was a slow gas evolution. Stirring was continued for 50 min. The mixture was then heated to reflux and held a t that temperature for 2 hr. The excess sodium hydride was decomposed by the addition of a small amount of methanol and the tetrahydrofuran was removed by distillation in a slow stream of nitrogen. The brown residue was dissolved in petroleum ether (b.p. 90-120") and washed with 20 ml. of water. The water layer was extracted with two 20-ml. portions of ether and the combined ether and petroleum ether extracts were dried over anhydrous sodium sulfate. By repeated concentration, cooling, and filtration there was obtained 1.93 g. (76.57,) of the desired product, m.p. 81-83'. Recrystallizat'ion from petroleum ether (b.p. 30-60") raised the melting point to 85.5-86 O. Anal. Calcd. for CllHllCIYN: C, 62.00; H, 4.37; C1, 28.12. Found: C, 61.62; H, 4.40; C1, 28.16. When the reaction was repeated on a larger scale a yield of 857, was realized. N-Methyl-2,2'-dibromodiphenylamine.-Following the above procedure, the S-methyl-2,2'-dibromodiphenylamine was prepared in 887, yield, m.p. 104-106" (lit.7cm.p. 106-109"). N-Ethyl-2,2'-dichlorodiphenylamine .-Following the above procedure, the ethyl derivative was prepared in 74.57, yield, m.p. 52-53'. Anal. Calcd. for C1dH1sClpIi: C, 63.37; H, 4.92; C1, 26.64; N, 5.26. Found: C, 63.35; H , 5.16; C1, 26.10; N, 5.25. N-Ethyl-2,2'-dibromodiphenylamine.-Following the above procedure the N-ethyl-2,2'-dibromodiphenylaminewas prepared in 83YGyield, m.p. 72-74" (lit.7bm.p. 72-74'). N-Ethyl-2,2'-dicarboxydiphenylamine .-A solution of N-methyl-2,2'-dibromodiphenylamine (10.67 g., 0.03 mole) in 50 ml. of freshly distilled tetrahydrofuran was slowly added to magnesium (1.70 g.-atom) in 20 ml. of tetrahydrofuran. The reaction was initiated with a few drops of ethyl bromide. The reaction was refluxed for 1 hr. and then poured over Dry Ice in diethyl ether. The mixture was acidified with 10% hydrochloric acid, the organic layer was separated and extracted with 5% potassium hydroxide. The water extracts were acidified with 10cj;, hydrochloric acid and extracted with ether. The ether layer was separated, dried over anhydrous sodium sulfate, and the solvent was removed to give 7 g. of a viscous oil. The oil was recrystallized from methanol to give 4.77 g. (55.8% crude) of product, m.p. 129-143". Two recrystallizations raised the melting point to 148.5-151 '. Anal. Calcd. for Cl,HlsNOl: C, 67.36; H, 5.30; N, 4.91; mol. wt., 285.3. Found: C, 67.41; H, 5.30; N, 5.05; mol. wt., 285. Preparation of 5-Methyl-10-phenyl-5,lO-dihydrophenophosphazine via Butyllithium Reaction .-A solution of n-butyllithium (0.04 mole) in diethyl ether was added a t ice-bath temperature to N-methyl-2,2'-dibro1nodiphenylamine(6.3 g., 0.0191 mole). Color Test IIlZwas negative after 1 hr. To the reaction mixture was added phenyldichlorophosphine (3.3 g., 0.018 mole) in 10 ml. of diethyl ether. The reaction mixture was stirred overnight a t room temperature, hydrolyzed, and extracted with ethyl (12) H. Gilman and J. Swiss, J . A m . Chem. Soc., 62, 1847 (1940).
341 1
acetate to give 3.1 g. (567,) of pale yellow crystals, m.p. 154157". Recrystallization from anhydrous ethanol raised the m.p. to 159-160". Anal. Calcd. for C19H16NP: C, 78.88; H, 5.57; N, 4.84; P , 10.71. Found: C, 78.92; H, 5.56; N, 4.85; P , 10.51. The 5,10-dihydrophenophosphazine formed a monomethyl iodide adduct in ethanol, m.p. 295-297' dec. Anal. Calcd. for Cp0H1gINP: C, 55.69; H, 4.44; I , 29.42; N, 3.25; P, 7.18. Found: C, 55.78; H, 4.43; I , 29.04; N, 3'.31; P , 7.23. Preparation of 5-Ethyl-10-phenyl-5,lO-dihydrophenophosphazine via Grignard Reaction 1.-A solution of N-ethyl-2,2'dibromodiphenylamine (10.67 g., 0.03 mole) in 45 ml. of freshly distilled tetrahydrofuran was added dropwise to magnesium (1.7 g., 0.07 g.-atom) in 5 ml. of tetrahydrofuran under a stream of dry nitrogen. The reaction was initiated with a few drops of ethyl bromide. After addition was completed, the reaction was refluxed for 2 hr. To the reaction mixture phenyldichlorophosphine (5.0 g., 0.028 mole) in 30 ml. of tetrahydrofuran was then added. Color Test I 1 3 was negative within 0.5 hr. The reaction mixture was refluxed overnight and then hydrolyzed by the addition of saturated aqueous ammonium chloride. Ethyl acetate was added; the mixture was filtered. The organic layer was separated and dried over anhydrous sodium sulfate, and the solvent was then removed to give a viscous oil which was recrystallized from 95% ethanol to yield 2.51 g. (27.57,) of product, m.p. 85-97'. Two successive recrystallizations from 9570 ethanol raised the melting point to 96.5-98.0". Anal. Calcd. for C2aHlaNP: C, 79.19; H , 5.98; N, 4.62. Found: C, 79.19; H, 5.95; N, 4.42. Preparation of 5-Ethyl-10-phenyl-5,lO-dihydrophenophosphazine via Grignard Reaction 11.-A few crystals of 1% were added to a slurry containing magnesium powder (0.72 g., 0.03 g.-atom), N-ethyl-2,2'-dichlorodiphenylamine (2.66 g., 0.01 mole), isopropyl alcohol (0.18 ml.), and freshly distilled tetrahydrofuran (5 ml.). The reaction was heated to 55" where slight frothing occurred and was then heated to 120' until the tetrahydrofuran was swept out. The reaction was cooled to 55" and isopropyl alcohol (0.20 ml.), tetrahydrofuran (5 ml.), and a few crystals of Ip were again added. After the initial frothing subsided an additional 25 ml. of tetrahydrofuran was added dropwise. After 2.5 hr., Color Test I was positive. To the reaction mixture was added phenyldichlorophosphine (1.70 g., 0.0095 mole) in tetrahydrofuran (17 ml.). The reaction was exothermic and Color Test I was negative after 45 min. The reaction was quenched with methanol and filtered. The methanol solution yielded a very gummy product which was extracted with 1 : 1 petroleum ether (b.p. 30-60") and methanol to give 0.428 g. (14.2%) of crude product, m.p. 82-97", Recrystallization from petroleum ether raised the melting point to 96-98'. (13) H. Gilman and F. Schulze, ibid., 47, 2002 (1925).
The Equilibrium Protonation and AcidCatalyzed Detritiation of Cyc1[3.2.2]azine1 ROBERTJ. THOMAS AND F . A. LONG Department of Chemistry, Cornell University, Ithaca, New Y o r k Received June 19, 1964
We have studied the equ'ilibrium protonation and acid-catalyzed detritiation of cycl[3.2.2]azine,I.* This inolecule possesses considerable resonance stabilization, undergoes electrophilic substitutioi~,~ and reversibly (1) Work supported by a grant from the Atomic Energy Commission. (2) T h e sample of I was kindly provided by Professor V. Roekelheide of the Department of Chemistry, University of Oregon, Eugene, Ore. (3) R. J. Windgassen, Jr., W. W. Saunders, J r . , and V. Boekelheide, J . A m . Chem. Sac., 81, 1469 (1959). (4) V. Boekelheide and T. Small, ibid., 83, 462 (1961).
NOTES
3412
protonates in strong acid to form a conjugate acid I I . 6 , 6 On this basis we have measured rate coefficients for the acid-catalyzed detritiation of I to ascertain whether its behavior will follow that established by trimethoxybenzene,' the azulenes,* and the methyl in dole^.^ In addition we have measured the acidity dependence for the equilibrium protonation of I as well as its thermodynamic ionization constant.
VOL. 29 TABLE I VARIATION I N k~ + WITH TEMPERATURE FOR THE HC1CATALYZED DETR~TIATION OF IO Temp., O C .
kH
+,
l./mole sec.
5.02 6.60 x 10-3 14.98 1.81 X 24.97 4 . 8 0 X 10+ 34.76 1 . 1 8 X 10-l ~r= 0.100 via added sodium chloride.
TABLE I1 ACTIVATION PARAMETERS FOR THE HYDRONIUM IONCATALYZED DETRITIATION O F CYCL[3.2.2]AZINE-I-t A N D AZULENE-I-La
I
I1
111
IV
The equilibrium protonation of I was measured spectrophotometrically in aqueous perchloric acid solutions. The data were treated by the method of Long and PaullO and the extrapolation to infinite dilution yielded a value of -2.82 f 0.10 for the pKa of I1 a t 25'. This is in good agreement with the value obtained by Gerson, et al., for the solvent system methyl alcohol-aqueous perchloric acid (1:4).5 This implies that I is a somewhat weaker base than azulene, whose conjugate acid has a pKa of -1.8. A plot of log indicator ratio us. -Hofor I has a slope of 1.87 f 0.08. The analogous plot for the equilibrium protonation of azulene, 111, has a slope of 1.80 f 0.12.* Thus, within experimental error, the equilibrium protonation of I arid 111 exhibits the same acidity dependence. This iniplies that the ratio of the activity coefficient of the base to that of the conjugate acid varies in the same manner with changes in medium for both I and 111. Both bases are unsubstituted aromatic conipounds and should not solvate to a large degree. Thus, their activity coefficients should not vary markedly with changes in medium. The conjugate acids, I1 and IV, are similar with respect to size, position of protonation, charge dispersal, and acidity of their methylene protons. On these grounds it seems plausible that, with changing medium, the variation in their activity coefficients due to changes in solvation would be similar. If the activity coefficient behavior is as described, the acidity function dependence for the equilibriGni protonation of I and 111 should be similar. Second-order rate coefficients for the hydrochloric acid-catalyzed detritiation of I were determined at four teiiiperatures.l1 The data are listed in Table I. The activation parameters generated from this data are shown in Table I1 together with the same data for azulene.* The almost identical results suggest that the acid-catalyzed detritiation of I and I11 occur by siniilar mechanisms. The detritiation of I in acetic acid buffers exhibits general acid catalysis. The second-order rate coeffi(5) F. Gerson, E. Heilbronner. N. Joop, and H. Zimmerman, Helu. C h m . Acta, 46, 1940 (1963). (6) V. Boekelheide. F. Gerson, E. Heilbronner. and D. Mueche, ibid., 46, 1951 (1963). (7) A. J. Kresge and Y . Chiang, J . Am. Chem. SOC.,81, 5509 (1959); 88, 2877 (1961). (8) J. Colapietro and F. A . Long, Chem. Ind. (London). 1056 (1960); J . Schulze and F. A . Long, J . Am. Chem. SOC.,86, 331 (1964); R . J. Thomas and F. A . Long, to be published. , 2524 (1963). (9) B. C. Challis and F. A . Long, J . A m . Chem. S O C . 85, B. C . Challis and F. A. Long, to be published. ( 1 0 ) F. .I.Long and M.A. Paul, Chem. Reu., 6'7, 1 (1957). (11) Tritiated I was prepared by the method of Schulze and Long?
CycI(3.2.2 ]azine-I-l
Azulene-I-t
E,, kcal./mole AS*, cal./deg. mole
16.5 16.0 -11.3 -10.1 A F * , kcal. /mole 19.2 19.0 a Rate constants used for these calculations had units of liter/ mole sec.
cient for acetic acid is 8.48 X l./mole sec. a t 25' while that for hydronium ion, Table I, is 4.80 X l./ mole see. a t 25'. For azulene the second-order rate coefficients a t 25' for the same species are 2.50 X lo-* and 0.181 l./mole sec., respectively. The ratio of the second-order rate coefficients, 111 divided by I, have values of 3.0 and 3.8 for acetic acid and hydronium ion, respectively. This implies similar Brgnsted generalacid-catalysis behavior, and is reasonable in view of their similar basicities. These results indicate that the detritiation of I occurs by the same slow proton-transfer process that has been established for azulene and triniethoxybenzene.
Reactions of Triphenylphosphinalkylimines with Boron Trifluoride' HANSZIMMERAND GURDIAL SINGH Department of Chemistry, University of Cincinnati, Cincinnati 81, Ohio Received March 84, 1964
Triphenylphosphinalkyliniines2 are strong nucleophiles. They readily react with alkyl hydrogen halides, and nitrosyl chloridese To further test their nucleophilicity t,hey were reacted with boron trifluoride. Under a perfectly dry nitrogen atmosphere, boron t,rifluoride reacted with triphenylphosphiiialkyliniines to give triphenylphosphiiialkyliniinetrifluoroboron complexes (I, Table I) ; but in the presence of moisture the only products isolated were the respective alkylamino(1) Presented in part a t the International Symposium on Boron-Nitrogen Chemistry, U. S. Army Research Office (Durham), Duke University, Durham, N. C., April, 1963; Abstracts of Papers, p. 216; Advances in Chemistry Series, Vol. 42, R. F. Gould, Ed., American Chemical Society, Washington, D. C., 1964, p. 17. (2) H. Zimmer and G. Singh, J . Org. Chem., 28, 483 (1963). (3) H. Staudinger and E. Hauser, Helu. Chim. Acla, 4 , 861 (1921). (4) L. Horner and H. Oedjger, Ann., 627, 142 (1959). ( 5 ) R. Appel and A. Hauss, Z . anow. allgem. Chem., 311, 290 (1961). (6) H. Zimmer and G. Singh, Angew. Chem., 7 6 , 574 (1963); Angew. Ckem., Intern. Ed. Engl.. 2, 395 (1963).
