Chemistry of 1.3-Butadiene-2,3-dicarbonitrile
J . Org. Chem., Vol. 43, No. 5, 1978 931
Whalley, J. Chern. Soc , 3722 (1955)] the NMR spectra of such a mixture should be more complicated than that obtained. W. F. Beech and H. A. Piggott. J. Chern. SOC., 423 (1 955). Further corroboration of this assignment is the slight shift in the opposite direction observed for the nitrile carbons. Although not as well demonstrated, steric perturbations apparently shift sp carbon resonances in a direction opposite to that found for sp3 carbons. See, e.g., G. C. Levy and G. L. Nelson, "Carbon-13 Nuclear Magnetic Resonance for Organic Chemists", Wiley-Interscience, New York. N.Y., 1972, p 130. See ref 4a and references cited therein. It is appropriate to note that the diene 1 undergoes facile polymerization to give an intractable and often dark-colored product under such diverse conditions as solution in or contact with dimethylformamide. dimethyl sulfoxide, triphenylphosphine, some samples of ethanol, acetone, acetonitrile, amine vapors, aqueous alkali, and often with alkali-metal salts of weak acids. These conditions allow a "normal" addition of diphenylamine to acrylonitrile: see, e.g., R. C. Cookson and F G. Mann, J. Chem. SOC., 67 (1949), and J. T. Braunholtz and F. G. Mann, ibid., 1817 (1953). By column chromatography, a small amount of an oily cyano (by IR) product was isolated which exhibited 'H NMR resonances at 6 7.0-7.6 and 1.2-1.9 (a pair of doublets superimposed on a multiplet) in a proton ratio of 3-4: 1. The resonances of the nonaromatic protons are too far upfield to correspond to any conceivable structure containing Ar2NCH2 and HCCN groups. While both €and Zisomers of 14 are possible, the single olefinic resonance suggests that only one IS present. No attemDt was made to determine this further. Addition of the amine at the y position (cf. eq 2), which may also occur, would not be observed, since proton abstraction and elimination would result in formation of the starting adduct
CT
\
I
CY
1
,NCH.CH--CCH
CY C" -+
I G R.
,\ NCH-C--OCH1
1
-
Formation of a sulfonate ester by this means is unprecedented. If this structure is correct, a mechanism involving participation of the sulfonate and cyano groups may be visualized:
22
Melting points (uncorrected) were recorded on a Mei-Temp apparatus: IR spectra were obtained on a Perkin-Elmer Mcdel 137 Infracord; NMR spectra (vs. internal Me4Si)were determined on Varian T60 and CFTPO instruments: mass spectra were recorded on a CEC 11OB instrument (70 eV). There was insufficient material for a careful analysis. However, the data available give substantial confirmation of the structure. The resonances for the methyl and allylic methylene hydrogens were complicated by long-range coupling effects. (a) Although not investigated, this oil may have been largely 12. (b) The shoulder on this resonance may be due to the presence of 12 as an imauritv. (21) ?he broad resonance at 6 7.5 is due to active proton exchange, while the narrow singlet at 6 7.5 represents the aldehydic and enolic protons. The two "quartets" at 6 3.7 and 4.0 are due to the methine hydrogens of respectively,and the integral ratio (1:1.4) suggests that the latter (enol form) predominates in the equilibrium,
CN CN
CN C l
I I -C-C-
1 1
,,NCHzC=CCH, \
I
I
/
H
NR,
Separation of these products by TLC was unsatisfactory. Analysis (by IR) of two isolated fractions showed strong cyanoenamine absorptions at ca. 2170 and 1640 cm-', but NMR studies of these same materials were equivocal. Crude product from a similar reaction of 10 and 11 with methylamine and with tert-butylamine also gave spectral evidence for the presence of a cyanoenamine. We are grateful to a referee for suggesting that amine participation would activate the y nitrile to protonation and hydrolysis, yielding 16 rather than the alternative I-( l-piperidino)-3-cyano-2-butene-2-carboxamlde.
CN Ch'
I 1
and
