Reactions of Phosphorus Compounds. X. The Reactions of halo Ketones and Nitriles with Tertiary Phosphines and Phosphites R. D. Partos and A. J. Speziale
Contribution f r o m Monsanto Company, Agricultural Division, Research Department, St. Louis, Missouri 63166. Received July 28, 1965 Stable enol phosphonium salts were isolated f r o m the reaction of certain a-haloacetophenones and triphenylphosphine. Pyrolysis and solvolysis of the enol phosphonium salts were also studied. The stereochemistry of the pyrolysis of IIb is discussed. Treatment of chlorodiphenylacetonitrile with triphenylphosphine led to the formation of an intermediate which, upon being treated with methanol, afforded the N-acylphosphinimine X I V . Treatment of chlorodiphenylacetonitrile with triethyl phosphite led to ketene imine X X I V and tetraphenylsuccinonitrile as a by-product. The formation of stable enol phosphonium salts, N-acylphosphinimine, ketenimine, and tetraphenylsuccinonitrile is interpreted mechanistically as involving the initial attack of the phosphorus compound at halogen in the halo ketone or nitrile. The reactions are discussed in terms of an intermediate ion pair.
a, R1= R2= CsHs b, R'=CBHB; R2=C1 C, R 1 = R 2 = C1
R' Cll f
I1
sorption, probably as a result of slight hydrolysis during transfers. Proton magnetic resonance analysis (n.m.r.) of salt IIa showed a multiplet centered at about 7 2.6. The P3I magnetic resonance spectrum exhibited a single peak at -63 p.p.m. relative to 85% phosphoric acid. a-Benzoyl-a-chlorobenzyltriphenylphosphonium chloride (IIIa) and the corresponding perchlorate IIIb
The reaction of trihaloacetamides with tertiary phosphines and phosphites has been shown to lead to trihalovinylamines via the halogenm igration reaction. This paper deals with the extension of this reaction to C6Hs a-haloacetophenones and nitriles. I CGHS-CO-C-P(CBH~)~ XEnol phosphonium salts have been p ~ s t u l a t e d ~ - ~ I as intermediates in the Perkowj and halogen migration CIAlthough these intermediates could be reactions. IIIa, X = CI b, X = Clod formed by attack of the phosphorus compound at carbonyl carbon3 or oxygen,'N6 it seems most likely were prepared in order to compare the enol phosphothat they are formed via a mechanism involving halogen nium salt IIb with its corresponding C-phosphonium attack. 2,7,8 salt. Salts IIIa and IIIb exhibited strong carbonyl Enol phosphonium salts have been reported preabsorption at 6.80 and 6.79 p , respectively. They were v i ~ u s l but y ~ ~little ~ physical data have been given in their considerably more stable to prototropic solvents than support. In a recent communicationg we reported the enol phosphonium salts. the first isolation and characterization of an enol phosSolvolysis of salts IIa, b, and c in aqueous methanol phonium salt-that obtained by treatment of chloroyielded the corresponding dehalogenated ketones in diphenylacetophenone (Ia) with triphenylphosphine. excellent yield (67-81 %). Treatment of chlorodiphenylacetophenone (Ia), dichlorophenylacetophenone (Ib), and trichloroacetoR' CsHj \ / phenone (IC) with triphenylphosphine leads to the formation in good yield (62-78 %), of enol phosphonium ,c=c\ L R2 OP(CsH6)a CI- + salts IIa, b, and c, respectively. Correct elemental R' analyses were obtained on all three hygroscopic salts. The infrared spectra showed only trace carbonyl abCH-cO-c6H5 + (CSH&~-OR c1/ ROH (1) A. J. Speziale and R. C. Freeman, J . Am. Chem. Soc., 82, 903 l l 2
/ ' R2
( 19 60).
(2) A. J. Speziale and L. R. Smith, ibid., 84, 1868 (1962). (3) M. S. Kharasch and I. S. Bengelsdorf, J . Org. Chem., 20, 1356 (1955). (4) I. J. Borowitz and L. I. Grossman, TetrahedronLetters, 471 (1962). ( 5 ) W. Perkow, Ber., 87, 755 (1954); W. Perkow, E. W. Krockow, and I
