SENJU EXHIBIT 2076
`LUPIN v SENJU
`IPR2015-01105
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`PAGE 1 OF 3
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`H30+-Catalyzed Hydrolysis of Amides
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`J. Am. Chem. Soc., Vol. 109, N0. 15, 1987
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`4621
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`Table I. Pseudo-First-Order Hydrolysis Rate Constants and 130-Exchange Data per 21/; Hydrolysis for Acetanilide at 72 °C, 11 = 1.0 M KCl
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`km
`% 130 found‘
`% ‘*0’
`kg,
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`(s" X 105)”
`at 11/;
`exchange/t,/2
`(s‘‘ X 107)’
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`262 :E 1
`54.57 :1: 0.07
`17.9 i 18.0
`0.5 :i: 0.5
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`54.50 :l: 0.07
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`54.45 :E 0.07
`54.44 i 0.03
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`53.40 i 0.10
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`53.25 :l: 0.10
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`51.70i0.10
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`51.60 :1: 0.10
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`51.54 :1: 0.10
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`51.32 4 0.08
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`51.42 i 0.04
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`51.41 4 0.09
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`A-9.16 :!: 0.06d
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`49.29 =e 0.03‘
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`49.22 :1: 0.12”
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`49.18 :E 0.08”
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`49.61 i 0.05
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`49.69 :1: 0.11
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`49.66 :1: 0.11
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`[Buffer-]" (M)
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`HCl, 1.0
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`HC1, 0.5
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`HC1, 0.1
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`HC1,0.05
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`146 i: 1
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`34.1 :i: 0.1
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`16.1 :l:0.1
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`10.4 :1: 0.1
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`10.0 3: 0.1
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`3.51 :E 0.01
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`3.56 i 0.01
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`1.15 :1: 0.02
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`1.07 d: 0.05
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`mean (%)
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`54.54 i 0.10
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`54.45 1: 0.07
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`53.32 :1: 0.20
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`51.65i:0.15
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`51.43 :l: 0.20
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`51.42 i 0.10
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`49.22 :1: 0.12
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`49.20 i 0.14
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`49.65 i 0.15
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`49.66 i 0.11
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`0.6 :l: 0.4
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`2.7 :E 0.7
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`5.7:l:0.6
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`13.5 :1: 9.1
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`13.5 d: 3.5
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`13.7:l: 1.5
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`6.1 :l: 0.7
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`6.1 :1: 0.5
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`7.7 :1: 0.5
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`7.7 :E 0.6
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`9.4 d: 0.6
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`9.4 i 0.5
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`9.5 :l: 1.10
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`9.2 :l: 0.84
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`4.1 :1: 0.28
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`4.1 :1: 0.34
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`1.64 :1: 0.13
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`1.5 i 0.36
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`glycine, 0.4
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`[11+] = 0.032
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`glycine, 0.1
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`[H+] = 0.032
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`glycine,‘ 0.4
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`[11+] = 0.01
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`glycine,‘ 0.2
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`[H*] = 0.01
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`glycine, 0.4
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`[H+] = 0.003
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`glycine, 0.2
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`[H*] = 0.003
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`" [H3O*] determined at 25 °C in the case of glycine buffers. ”Determined by observing rate of change of absorbance at 240 nm in duplicate. Rate
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`constants derived from nonlinear least-squares fitting of Abs vs. time data to standard exponential model. Error limits from least-squares standard
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`deviations.
`‘Initial 150 content determined by isolation of labeled acetanilide at time 0 from 1 N HCl solution (54.73 i 0.09; 54.87 :1: 0.08; mean
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`= 54.80 :1: 0.15).
`‘New sample labeled acetanilide used in this run; 130 content by isolation from glycine at time 0 (53.37 i 0.08; 53.30 t 0.09;
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`mean = 53.34 :l: 0.14).
`‘Normalized to 100% ‘S0 at time 0. Error limits calculated as sum of standard deviations of the mean plus that of time 0
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`sample normalized to 100%. /Calculated from percent 130 content at 23/2 hydrolysis as in text; error limits are cumulative sums of standard devia-
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`tions in '30 content and km.
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`Table II. Pseudo-First-Order Hydrolysis Rate Constants and “‘O—Exchange Data per t,/2 Hydrolysis for N-Cyclohexylacetamide at 100 °C, 11 =
`1.0 M KCl
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`khyd
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`(S-1 X 106)“
`53 :l: 2
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`27.7 :.E 1.0
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`2.85 :1: 0.04
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`[HC1]
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`1.0
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`0.2
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`0.1
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`0.05
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`0.02
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`0.01
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`% 180 fOUI‘1db
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`at t1/2
`50.11 :E 0.04
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`50.13 i: 0.02
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`mean (%)
`50.12 i 0.05
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`% 180
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`exchange‘/t1/2
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`1.05 :1: 0.3
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`1...
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`(s'1 X 108)”
`80.4 :1: 27.0
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`49.37 i 0.13
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`48.20 i: 0.17
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`47.85 :1: 0.20
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`46.80 i 0.20
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`46.10 i 0.10
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`2.5 :l: 0.5
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`4.8 :l: 0.5
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`5.5 :1: 0.6
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`7.6 :l: 0.6
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`9.0 :.E 0.4
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`42.1 d: 10.5
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`40.7 i 6.3
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`23.4 i 3.7
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`13.0 :1: 1.7
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`7.7 :1: 0.7
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`49.45 :l: 0.05
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`49.30 i 0.04
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`48.19 :l: 0.04
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`43.21 :l: 0.16
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`47.80 i 0.10
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`47.90 :E 0.15
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`46.70 :E 0.10
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`46.90 :1: 0.10
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`46.08 i 0.05
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`46.10 :2 0.10
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`“km determined by ‘H NMR analysis according to the method of Williams? ”Sample separated at time 0 from 1 M HCl (50.72 :1: 0.04; 50.59
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`i 0.03; mean = 50.65 :1: 0.11).
`‘Normalized to 100% ‘SO-enriched sample at time 0. Error limits calculated as sum of standard deviations of the
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`mean plus that of time 0 sample normalized to 100%.
`‘Calculated from percent 130 content at 11/2 hydrolysis; where khyd is not given it was
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`calculated assuming a first-order dependence in [H3O*] and a i5% error, which is factored into kex.
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`with saturated NaCl until the aqueous layer was neutral. The organic
`The depletion is expressed as percent of ‘*0 exchange per t1/2
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`layer was dried (MgSO4) and stripped of solvent to yield a residue which
`hydrolysis (normalized to 100% enrichment at zero time) in
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`was subjected to direct mass spectrometric analysis with an AEI MS-12
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`column five. Given in column six are the kex values, calculated
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`low-resolution mass spectrometer. The “*0 content of the reisolated
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`according to kextl/2 = ln (a/a — x), where a and a — x are the ‘SO
`material was calculated as (IM++2)/(IM++2 + IM+), where I is the peak
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`contents at zero time and t,/2, respectively. The error limits in
`intensity of the parent and enriched parent ions. Nine to sixteen separate
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`kex are calculated based on the cumulative standard deviations
`determinations of the M* and M* + 2 intensities were recorded. Primary
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`data are given in the supplementary material (Tables 1S and 2S). Values
`in both 130 contents and km. The errors are largest at low
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`amounts of exchange and less so at high amounts, but their in-
`given in Tables I and II are the averages of two independent determi-
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`nations along with the cumulative standard deviations. As a check to
`clusion does not alter the conclusion that the amount of exchange
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`exclude anomalous exchange during the extraction and analysis proce-
`increases as [H3O+] decreases.
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`dure, the 130 content of three independent samples removed at t = 0 was
`Finally, shown in Figure 1 is a plot of log kex and log khyd vs.
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`determined and compared with that of authentic material:
`in no case was
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`—log [H3O*] for both amides. The point of note is that the log
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`the ‘*0 content different within the experimental accuracy.
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`kex values for both amides tend to plateau at high [H3O*] but
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`Results
`tend to a first-order dependence at low [H3O*].‘°-”
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`Given in Tables I and II are hydrolytic rate constants and mass
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`spectrometric ‘*0-exchange data for ~50% labeled 2 and 3
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`reisolated from solution at the hydrolytic 23/2 at various [H3O*].
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`Duplicate isolation experiments were performed, and the error
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`limits quoted in column three of Tables I and II are the standard
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`deviations of 9-16 scans of the M*' and M’' + 2 peaks. From the
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`mean values in column four it is readily seen that an increasing
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`depletion of 180 content occurs at lower [H3O+] for both amides.
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`PAGE 2 OF 3
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`(10) As with other reported amides,”’~2“'” the km values for 2 and 3 show
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`significant deviations from linearity at high [H3O*].
`In the regions where
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`significant increases in “*0 exchange occur, a first-order dependence of km
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`on [H*] obtains.
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`(11) (a) Barnett, J. W.; Hyland, C. J.; O’Connor, C. J. J. Chem. Soc.,
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`Chem. Commun. 1972, 720.
`(b) Barnett, J. W.; O’Connor, C. J. J. Chem.
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`Soc., Perkin Trans. 2 1972, 2378; 1973, 220.
`(c) Modro, T. A.; Yates, Ks,
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`Beaufays, F. Can. J. Chem. 1977, 55, 3050.
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`PAGE 2 OF 3
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`-0.50
`-8.00 -7.00
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`logk(s—1)
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`2.50
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`-0.50
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`0.50
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`1.50
`—log[H+]
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`Figure 1. Plots of log km (*) and log kex (0) vs. —1og [H3O*'] for
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`N-cyclohexylacetamide (A) and acetanilide (B) determined at 100 and
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`72 °C, respectively, /1. = 1.0 M KCl. The k,,, values are calculated from
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`percent 150 content at t,/; hydrolysis (see text). Dashed error bars in
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`exchange data of B indicate there is no satisfactory lower limit clue to
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`error limits exceeding the value of k,,,. Straight lines through km data
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`are unit slope first-order dependence on [H3O*'].
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`Discussion
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`Changes in C-O/C-N cleavage ratios as a function of pH have
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`been noted in acid-catalyzed hydrolyses of certain imidate esters”
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`and amide acetals‘“"” and have been explained in terms of the
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`involvement of tetrahedral intermediates differing in the site and
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`state of protonation. In those cases, the C-O/C-N cleavage ratio
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`increases at lower [H3O"']. Although phenomenologically a similar
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`situation is observed with 2 and 3, C-0 cleavage regenerates amide
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`(labeled or unlabeled), which ultimately hydrolyzes.
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`With the exception of McClelland’s observations with benz-
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`amide (0.2% 130 loss/t,/2, 5.9% HZSO4, 85 °C),““ the occurrence
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`of 180 exchange accompanying acid-catalyzed amide hydrolysis
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`has not been demonstrated. Such exchange is well documented
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`(12) (a) Smith, V. F.; Schmir, G. L. J. Am. Chem. Soc. 1975, 97, 3171.
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`(b) Caswell, M.; Schmir, G. L. Ibid. 1979, 101, 7323.
`(c) Lee, Y. N.; Schmir,
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`G. L. lbid. 1979, 101, 6277.
`(d) Chaturvedi, R. K.; Schmir, G. L. Ibid. 1968,
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`90, 4413.
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`(13) McClelland, R. A.; Patel, G. Ibid. 1981, 103, 6908.
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`(14) (a) Bunton, C. A.; Nyak, B.; O‘Connor, C. J. J. Org. Chem. 1968,
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`33, 572. (b) Bender, M. L.; Thomas, R. J. J. Am. Chem. Soc. 1961, 83, 4183.
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`(b)
`(15) (a) Shain, S. A.; Kirsch, J. F. J. Am. Chem. Soc. 1968, 90, 5848.
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`Lane, C. A.; Cheung, M. F.; Dorsey, G. F. Ibid. 1968, 90, 6492.
`(c) For a
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`review of early oxygen isotopic exchange reactions of organic compounds, see:
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`Samuel, D.; Silver, B. L. Adv. Phys. Org. Chem. 1965, 3, 123-186.
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`PAGE 3 OF 3
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`Slebocka- Tilk et al.
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`in base hydrolysis,1v'4 as well as in both acid and base hydrolysis
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`of carboxylic esters,‘v‘5 and has been traditionally interpreted as
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`implying the intermediacy of reversibly formed tetrahedral in-
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`termediates.
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`The generally accepted mechanism for amide hydrolysis in acid
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`involves H20 attack on an O-protonated amide” to produce a
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`tetrahedral addition intermediate which undergoes rapid N-
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`protonation and subsequent irreversible C—N cleavage (eq 1).
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`\ +°*H “,0 \
`°“ __\. °“
`/N
`R
`:21’. /N-i—-Fi ._
`H/9\H
`ll
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`H OH
`/
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`(1)
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`O
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`\ _<°
`N
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`R
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`+ H
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`.,
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`+
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`>\\
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`R
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`HO
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`\ /H
`N
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`/1+
`H
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`Our present results require that there be at least one inter-
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`mediate (not necessarily given in eq 1) that is in equilibrium with
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`starting amide and allows oxygen exchange. There are two major
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`considerations in both quantitating the exchange data and relating
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`it to the hydrolytic process. The first assumes that the inter-
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`mediates are at equilibrium with respect to proton transfer. Thus,
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`if there is a reversibly formed amide hydrate, both oxygens have
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`an equivalent probability for loss (exclusive of C-150/C-180
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`kinetic isotope effects). The fact that changes in [glycine buffer]
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`at low [H3O+] affect neither khyd nor kex suggests the various
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`intermediates are at equilibrium with respect to proton transfer,
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`at least in the case of acetanilide.
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`A second and perhaps more serious assumption is that the
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`intermediate leading to exchange is on the hydrolytic pathway."“"
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`Inasmuch as microscopic adherance to eq 1 requires that the
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`transition states leading to C-0 or C—N cleavage each have the
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`same molecular composition, (H+, OH2, amide), with that scheme
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`it is difficult to explain why the k,,, and khyd rate constants diverge
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`as a function of [H3O+]. Perhaps this indicates that there are
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`two parallel processes, one leading to exchange and another to
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`hydrolysis.
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`More work is clearly required to determine the scope, limitation,
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`and structural constraints on the exchange process prior to pro-
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`posing a scheme which explains these findings. Nevertheless, the
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`observation of significant exchange accompanying acid-catalyzed
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`hydrolysis of these two amides challenges our current under-
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`standing of this important process.
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`Acknowledgment. We thank the University of Alberta and the
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`Natural Sciences and Engineering Research Council of Canada
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`for generous financial support. We are particularly grateful to
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`the referees of this manuscript and to Professor R. L. Schowen,
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`whose inciteful comments prompted a reevaluation of the phe-
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`nomenon of 180 exchange accompanying amide hydrolysis.
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`Supplementary Material Available: Tables 1S and 2S of original
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`mass spectrometric intensity data for 2 and 3 at various [H3O+]
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`(10 pages). Ordering information is given on any current
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`masthead page.
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`4622
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`J. Am. Chem. Soc., Vol. 109, No. 15, 1987
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`~4.00
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`-5.00
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`logk(s—1)
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`-6.00
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`-7.00
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`-8.00
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`-3.00
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`-4.00
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`-5.00
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`PAGE 3 OF 3