Diastereoselective synthesis of stable phosphorus ylides by a three-component reaction between triphenylphosphine, dialkyl acetylenedicarboxylates and 3-(arylsulfonylhydrazono)butanoates

Article abstract of DOI:10.3184/174751913X13692122845243

Protonation of the reactive 1:1 intermediate produced in the reaction between dialkyl acetylenedicarboxylates and triphenylphosphine by 3-(arylsulfonylhydrazono)butanoates leads to vinylphosphonium salts which undergo Michael addition with the conjugate base of the CH-acid to produce highly functionalised, salt-free phosphorus ylides in a diastereoselective manner and excellent yields.

Full text of DOI:10.3184/174751913X13692122845243

JOURNAL OF CHEMICAL RESEARCH 2013
RESEARCH PAPER 385
JULY, 385–387
Diastereoselective synthesis of stable phosphorus ylides by a
three-component reaction between triphenylphosphine, dialkyl
acetylenedicarboxylates and 3-(arylsulfonylhydrazono)butanoates
Mohammad Anary-Abbasinejad*, Mahdiyeh Talebizadeh and Fereshteh Nikmehr
Department of Chemistry, Vali-e-Asr University, Rafsanjan, 77176, Iran
Protonation of the reactive 1:1 intermediate produced in the reaction between dialkyl acetylenedicarboxylates and
triphenylphosphine by 3-(arylsulfonylhydrazono)butanoates leads to vinylphosphonium salts which undergo Michael
addition with the conjugate base of the CH-acid to produce highly functionalised, salt-free phosphorus ylides in a
diastereoselective manner and excellent yields.
Keywords: diastereoselective synthesis, dialkyl acetylenedicarboxylates, phosphorus ylides, triphenylphosphine, CH-acid
Phosphorus ylides are organic systems, which have attracted
attention from chemists due to their value for the synthesis
of a wide range of naturally occurring and industrially, bio-
logically and pharmaceutically active compounds.1–3 Several
methods have been utilised for the synthesis of phosphorus
ylides, the most important of which is the deprotonation of
phosphonium salts with a base.1,2 Addition of triphenylphos-
phine to activated acetylenes has been reported to produce a
reactive zwitterionic intermediate which could be trapped by
carbon–electrophiles or by a proton to produce phosphorus
ylides, which may be isolated as stable compounds or undergo
further intramolecular reactions to produce a wide range of
carbocyclic or heterocyclic compounds.4–13 In the course of our
ongoing study of the reaction between trivalent phosphorus
nucleophiles and acetylene diesters in the presence of an
electrophile,7–13 we now report an efficient method for the dia-
stereoselective synthesis of some phosphorus ylides by a three-
component reaction between dialkyl acetylenedicarboxylates,
triphenylphosphine and 3-(arylsulfonyl)hydrazono)butanoates
(Scheme 1).
95% yield. The structure of compound 4a was confirmed by
spectroscopic and analytical data.
The NMR spectra of ylide 4a are consistent with the
presence of two rotamers. The ylide moiety of this compound
is strongly conjugated with the adjacent carbonyl group and
rotation around the C–C bond due to its partial double bond
character is slow on the NMR time scale at room temperature
(Scheme 2). The 1H NMR spectrum of compound 4a displayed
two sharp lines at 0.92 and 1.40 ppm for two t-butyl groups
and a singlet at 1.86 ppm for the methyl group. The protons of
the ethyl group were observed at 0.89 and 3.56 ppm as mul-
tiple signals for two rotamers of 4a. The methine proton adja-
cent to the ylide moiety was observed as a double doublets
(3JHH = 11 Hz, 2JHP = 18 Hz) at 3.02 ppm and the other methine
proton was observed as a doublet (3JHH = 11 Hz) at 4.72 ppm.
A D2O-exchangeable broad singlet was observed at 6.76 ppm
for the NH proton. The aromatic protons were observed
at 6.90–7.90 ppm as multiplet signals. Similar signals were
observed for the other rotamer at the appropriate chemical
shifts (see Experimental). The 13C NMR spectrum of com-
pound 4a showed 22 signals consistent with the proposed
structure. The 31P NMR spectrum of compound 4a showed a
signal at 25.9 ppm which is consistent with those observed
for stable phosphorus ylides.14,15 The proposed structure for
compound 4a was further supported by the IR spectrum. The
Results and discussion
Reaction of triphenylphosphine and di(t-butyl) acetylenedicar-
boxylate(DTAD)inthepresenceofethyl3-(2-(phenylsulfonyl)-
hydrazono)butanoate leads to the corresponding ylide 4a in
Scheme 1 Reaction between triphenylphosphine, dialkyl acetylenedicarboxylates and 3-(arylsulfonylhydrazono)butanoates.
* Correspondent. E-mail: m.anary@vru.ac.ir;
manaryabbasinejad@gmail.com

386 JOURNAL OF CHEMICAL RESEARCH 2013
Synthesis of compounds 4a–e; general procedure
A mixture of dialkyl acetylenedicarboxylate (1 mmol) in dichloro-
methane was added dropwise to a magnetically stirred solution of
triphenylphosphine(1mmol)andethyl3-(2-(arylsulfonyl)hydrazono)-
butanoate (1 mmol) in dichloromethane (10 mL) (3 mL) at room
temperature over 2 min. The reaction mixture was then stirred for
24 h. The solvent was evaporated under reduced pressure. The solid
was washed with diethyl ether to give the pure product.
1,2-di-tert-Butyl3-ethyl4-(2-(phenylsulfonyl)hydrazono)-1-(triphenyl-
phosphoranylidene)pentane-1,2,3-tricarboxylate (4a): Yield: 95%;
white powder; m.p. 142–143 ˚C. IR (KBr) (ῡmax, cm−1): 3180 (NH),
1720, 1710, 1622 (ester groups). Anal. Calcd for (C42H49N2O8PS): C,
65.27; H, 6.39; N, 3.62. Found: C, 65.6; H, 6.2; N, 3.9%. Major isomer
Scheme 2 Geometrical isomers (rotamers) of compound 4.
carbonyl region of the spectrum exhibited strong absorptions
at 1720, 1710 and 1622 cm–1 for the carbonyl groups. Com-
pound 4a possesses two chiral centres and two diastereoiso-
mers might be expected. However, the NMR data show the
existence of only one isomer. We could not distinguish the
relative configuration of the product from an analysis of
the NMR spectra of compound 4a.
To explore the scope of the reaction, triphenylphosphine
was treated with DTAD (2a), diethyl acetylenedicarboxylate
(DEAD, 2b) or dimethyl acetylenedicarboxylate (DMAD, 2c)
in the presence of ethyl 3-(2-phenylsulfonylhydrazono)butano
ate (3a) or ethyl 3-(2-tosylhydrazono)butanoate (3b) and
the corresponding phosphoranes 4a–e were obtained in good
yields. All the above reactions are diastereoselective and
comparing the coupling constants and chemical shifts in the
NMR spectra of these compounds showed that their relative
configurations are the same.
A reasonable mechanism for the formation of the phospho-
ranes 4 is presented at Scheme 3. The addition of triphe-
nylphosphine to dialkyl acetylenedicarboxylate (DAAD) 3 and
subsequent protonation of the 1:1 adduct 5 by ethyl 3-(arylsul-
fonylhydrazono)butanoate 1 afforded the phosphonium inter-
mediate 6. The positively charged ion 6 is then attacked by the
anion 7 to form the phosphorane 4.
In summary, we have reported that the three-component
reaction between dialkyl acetylenedicarboxylates, triphenyl-
phosphine and ethyl 3-(arylsulfonylhydrazono)butanoates
leads to a diastereoselective synthesis of functionalised
phosphoranes in good yields. The advantages of the reported
method are simple available starting materials, simple
work-up, neutral reaction conditions and high yields.
1
(60%): H NMR (CDCl3, 400 MHz): δ 0.89 (3H, m, CH3)*, 0.92
(9H, s, t-Bu), 1.40 (9H, s, t-Bu), 1.86 (3H, s, CH3), 3.02 (1H, dd 3JHH
2
3
= 11 Hz, JHP = 18 Hz, CH), 3.56 (2H, m, CH2)*, 4,72 (1H, d JHH
=
11 Hz, CH), 6.76 (1H, s, NH), 6.90–7.90 (20H, m, aromatic). 13C
NMR (CDCl3, 100 MHz): δ 13.7 (CH3), δ 17.5 (CH3-C=N), 28.1 and
28.2 (2 t-Bu), 44.8 (d, 1JPC = 59 Hz, C=P) 52.7 (d, 2JPC = 5 Hz, CH),
60.2 (CH–C=O), 65.5 (OCH2), 79.8 and 77.2 (2 t-Bu), 126.08 (d, 1JPC
= 91 Hz, Cipso), 128.9 (d,3JPC = 10 Hz, Cmeta), 132.53 (Cpara), 134.5 (d,
2JPC = 6 Hz, Cortho), 128.1, 128.3, 129.3, 142.6 (N-Ph), 154.1 (C=N),
2
166.2 (C=O), 170.5 (C=O), 174.1 (d, JPC = 7 Hz, C=O). 31P NMR
(CDCl3): δ = 25.9. Minor isomer (40%): 1H NMR (CDCl3, 400 MHz):
δ 0.89 (3H, m, CH3)*, 1.38 (9H, s, t-Bu), 1.46 (9H, s, t-Bu), 1.76 (3H,
s, CH3), 3.00 (1H, dd 3JHH = 11 Hz, 2JHP = 20 Hz), 3.56 (2H, m, CH2)*,
4,33 (1H, d 3JHH = 11 Hz, CH), 6.79 (1H, s, NH), 6.90–7.90 (20H, m,
aromatic)*. 13C NMR (CDCl3): δ 13.9 (CH3), δ 17.6 (CH3–C=N), 28.0
1
2
and 28.3 (2 t-Bu), 44.5 (d, JPC = 59 Hz, C=P), 53.1 (d, JPC = 5 Hz,
CH), 59.9 (CH–C=O), 65.3 (OCH2), 79.6 and 77.0 (2 t-Bu), 126.1 (d,
1JPC = 91 Hz, Cipso), 128.9 (d,3JPC = 10 Hz, Cmeta), 132.6 (Cpara), 134.4
(d, 2JPC = 6 Hz, Cortho), 128.5, 128.8, 129.1, 143.2 (N-Ph), 154.8 (C=N),
2
166.4 (C=O), 171.5 (C=O), 174.9 (d, JPC = 7 Hz, C=O). 31P NMR
(CDCl3): δ = 25.7 (* for two isomers).
1-tert-Butyl 5-ethyl 3-pivaloyl-4-(1-(2-tosylhydrazono)ethyl)-2-
(triphenylphosphoranylidene)pentanedioate (4b): Yield: 90%; white
powder; m.p. 138–139 ˚C. IR (KBr) (ῡmax, cm−1): 3221 (NH), 1720,
1709, 1617 (ester groups). Anal. Calcd for (C43H51N2O8PS): C, 65.63;
H, 6.53; N, 3.56. Found: C, 65.5; H, 6.3; N, 3.9%. Major isomer
(60%): 1H NMR (CDCl3, 400 MHz): δ 0.82 (3H, m, CH3), 0.93 (9H,
s, t-Bu), 1.42 (9H, s, t-Bu), 1.85 (3H, s, CH3), 2.37 (3H, s, CH3), 3.07
(1H, dd 3JHH = 11 Hz, 2JHP = 18 Hz), 3.56 (2H, m, CH2), 4.71 (1H, d
3JHH = 11 Hz, CH), 6.76 (1H, s, NH), 7.10–7.90 (19H, m, aromatic)*.
13C NMR (CDCl3, 100 MHz): δ 13.7 (CH3), δ 17.3 (CH3–C=N),
21.4 (CH3), 28.1 and 28.3 (2 t-Bu), 44.7 (d, 1JPC = 59 Hz, C=P), 52.3
(d, 2JPC = 5 Hz, CH), 60.1 (CH–C=O), 65.5 (OCH2), 79.4 and 77.3 (2
t-Bu), 126.1 (d, 1JPC = 91 Hz, Cipso), 128.9 (d,3JPC = 10 Hz, Cmeta), 132.5
2
Experimental
(Cpara), 134.3 (d, JPC = 6 Hz, Cortho), 128.1, 128.2, 129.3, 143.5
Melting points were determined with an Electrothermal 9100 apparatus.
Elemental analyses were performed using a Heraeus CHNO-Rapid
analyser. IR spectra were recorded on a Shimadzu IR-470 spectrom-
(N-aromatic), 156.9 (C=N), 166.2 (C = O), 170.4 (C=O), 174.1 (d,
2JPC = 7 Hz, C=O). 31P NMR (CDCl3): δ = 25.6. Minor isomer (40%):
1H NMR (CDCl3, 400 MHz): δ 0.84 (3H, m, CH3), 1.28 (9H, s, t-Bu),
1.45 (9H, s, t-Bu), 1.76 (3H, s, CH3), 2.39 (3H, s, CH3), 3.05 (1H,
1
eter. H and 13C NMR spectra were recorded on Bruker DRX-400
dd 3JHH = 11 Hz, 2JHP = 18 Hz), 3.78 (2H, m, CH2), 4.32 (1H, d 3JHH
=
Avance spectrometer at solution in CDCl3 or d6-DMSO using TMS as
internal standard.
11 Hz, CH), 6.75 (1H, s, NH), 7.10–7.90 (19H, m, aromatic). 13C
Scheme 3 The suggested mechanism for formation of phosphorane 4.

JOURNAL OF CHEMICAL RESEARCH 2013 387
NMR (CDCl3): δ = 14.1 (CH3), 17.3 (CH3–C=N), 21.7 (CH3), 28.2
(C=N), 169.7 (C=O), 172.1 (C=O), 174.7 (d, 2JPC = 5 Hz, C=O) (* for
two isomers).
1
2
and 28.9 (2 t-Bu), 44.9 (d, JPC = 59 Hz, C=P) 52.7 (d, JPC = 5 Hz,
CH), 60.2 (CH–C=O), 65.2 (OCH2), 79.5 and 77.0 (2 t-Bu), 126.1 (d,
1JPC = 91 Hz, Cipso), 128.7 (d,3JPC = 10 Hz, Cmeta), 132.4 (Cpara), 134.1
(d, 2JPC = 6 Hz, Cortho), 127.8, 128.7, 129.4, 143.9 (N-aromatic), 152.4
3-Ethyl 1,2-dimethyl 4-(2-phenylsulfonylhydrazono)-1-(triphenyl-
phosphoranylidene)pentane-1,2,3-tricarboxylate (4e): Yield: 90%;
white powder; m.p. 177–178 ˚C. IR (KBr) (ῡmax, cm−1): 3123 (NH),
1732, 1598 (ester groups). Anal. Calcd for (C36H37N2O8PS): C, 62.78;
H, 5.41; N, 4.07. Found: C, 62.5; H, 5.5; N, 3.8%. Major isomer
(C=N), 166.2 (C=O), 171.4 (C=O), 174. 3 (d, 2JPC = 7 Hz, C=O). 31
P
NMR (CDCl3): δ = 25.1 (* for two isomers).
1
(60%): H NMR (d6-DMSO, 400 MHz): δ 0.87 (3H, m, CH3)*, 1.47
Triethyl 4-(2-(phenylsulfonyl)hydrazono)-1-(triphenylphosphoranyl-
idene)pentane-1,2,3-tricarboxylate (4c): Yield: 95%; white powder;
m.p. 175–176 ˚C. IR (KBr) (ῡmax, cm−1): 3121 (NH), 1745, 1728, 1597
(ester groups). Anal. Calcd for (C38H41N2O8PS): C, 63.67; H, 5.77; N,
3.91. Found: C, 63.6; H, 5.5; N, 3.9%. Major isomer (60%): 1H NMR
(d6-DMSO, 400 MHz): δ 0.22 (t, 3H, 3JHH = 8 Hz, CH3), 0.69–1.01 (m,
6H, 2 CH3)*, 1.47 (s, 3H, CH3), 2.77 (1H, m, CH)*, 3.42–3.88 (m,
(3H, s, CH3), 2.88 and 3.38 (6H, 2 s, 2 OCH3), 2.96 (1H, m, CH)*, 3.84
(2H, m, O–CH2)*, 4.23 (d, 1H, 3JHH = 11 Hz, CH), 7.32–7.69 (20H, m,
aromatic)*, 10.20 (1H, s, N–H). 13C NMR (CDCl3, 100 MHz): δ 13.6,
1
(CH3), 17.0 (CH3–CN), 43.6 (d, JPC = 110 Hz, C=P), 49.4 and 51.2
1
(2 OCH3), 53.7 (CH), 59.6 (OCH2), 127.2 (d, JPC = 90 Hz, Cipso),
134.2 (d,3JPC = 10 Hz, Cmeta), 132.3 (d, 2JPC = 6 Hz, Cortho), 132.5 (Cpara),
1
3
6H, O–CH2)*, 4.12 (d, H, JHH = 11 Hz, CH), 7.43–7.70 (20H, m,
aromatic)*, 10.06 (1H, s, N–H). 13C NMR (d6-DMSO, 100 MHz): δ
13.5, 13.6, 13.7, 13.9, 14.0, 14.2 (3 CH3)*, 15.0 (CH3–CN), 42.8 (d,
127.3, 131.5, 131.8, 139.4 (N-aromatic), 154.8 (C=N), 169.3 (C=O),
2
1
170.8 (C=O), 174.3 (d, JPC = 7 Hz, C=O). Minor isomer (40%): H
NMR (CDCl3, 400 MHz): δ 0.87 (3H, m, CH3)*, 1.50 (3H, s, CH3),
3.35 and 3.51 (6H, 2 s, 2 OCH3), 2.96 (1H, m, CH)*, 3.84 (2H, m,
1JPC = 60 Hz, C=P), 52.1 (d, 2JPC = 5 Hz, CH), 57.1, 59.9, 60.1, 60.5,
O–CH2)*, 4.46 (d, H, JHH = 11 Hz, CH), 7.32–7.69 (20H, m, aro-
1
3
1
65.1, 65.3 (3 OCH2)*, 126.2 (d, JPC = 91 Hz, Cipso), 133.6 (d,3JPC
=
matic)*, 10.24 (1H, s, N–H). 13C NMR (CDCl3, 100 MHz): δ 13.8,
10 Hz, Cmeta), 131.9 (d, 2JPC = 6 Hz, Cortho), 132.5 (Cpara), 127.3, 131.4,
1
(CH3), 16.8 (CH3–CN), 43.5 (d, JPC = 110 Hz, C=P), 51.0 and 48.3
132.5, 139.4 (NH-aromatic), 154.2 (C=N), 169.6 (C=O), 170.8 (C=O),
1
2
1
(2 OCH3), 52.1 (CH), 59.8 (OCH2), 127.4 (d, JPC = 90 Hz, Cipso),
174.2 (d, JPC = 7 Hz, C=O). Minor isomer (40%): H NMR (d6-
134.2 (d,3JPC = 10 Hz, Cmeta), 132.3 (d, 2JPC = 6 Hz, Cortho), 132.5 (Cpara),
127.0, 131.4, 131.9, 139.5 (N-aromatic), 154.9 (C=N), 169.8 (C=O),
170.7 (C=O), 174.2 (d, 2JPC = 7 Hz, C=O) (* for two isomers).
3
DMSO, 400 MHz): δ 0.68 (t, 3H, JHH = 8 Hz, CH3), 0.69–1.01 (m,
6H, 2 CH3)*, 1.34 (s, 3 H, CH3), 2.77 (1H, m, CH)*, 3.42–3.88 (m,
6H, O–CH2)*, 4.35 (d, 1H, JHH = 11 Hz, CH), 7.43–7.70 (20H,
3
m, aromatic)*, 10.04 (1H, s, N–H). 13C NMR (CDCl3, 100 MHz):
δ 13.5, 13.6, 13.7, 13.9, 14.0 (3 CH3)*, 15.2 (CH3–CN), 42.5 (d, 1JPC
=
Received 15 March 2013; accepted 12 April 2013
Paper 1301837 doi: 10.3184/174751913X13692122845243
Published online: 18 July 2013
2
60 Hz, C=P), 52.7 (d, JPC = 5 Hz, CH), 57.1, 59.9, 60.1, 60.5, 65.1,
65.3 (3 OCH2)*, 127.1 (d, 1JPC = 91 Hz, Cipso), 134.2 (d,3JPC = 10 Hz,
C
meta), 132.2 (d, 2JPC = 6 Hz, Cortho), 132.5 (Cpara), 127.4, 132.4, 133.5,
141.4 (NH-aromatic), 154.5 (C=N), 169.0 (C=O), 172.1 (C=O), 174.2
(d, 2JPC = 5 Hz, C=O) (* for two isomers).
References
1
2
3
4
R. Engel, Synthesis of carbon-phosphorus bonds. CRC Press, Boca Raton,
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Triethyl4-(2-tosylhydrazono)-1-(triphenylphosphoranylidene)pent-
ane-1,2,3-tricarboxylate (4d): Yield: 95%; white powder; m.p. 177–
178 ˚C. IR (KBr) (ῡmax, cm−1): 3125 (NH), 1729, 1597 (ester groups).
Anal. Calcd for (C39H43N2O8PS): C, 64.10; H, 5.93; N, 3.83. Found:
1
C, 63.8; H, 5.9; N, 4.1%. Major isomer (60%): H NMR (CDCl3,
3
400 MHz): δ 0.32 (t, 3H, JHH = 7 Hz, CH3), 0.69–1.31 (m, 6H,
2 CH3)*, 1.45 (s, 3H, CH3), 2.34 (3H, s, CH3), 2.88 (1H, m, CH)*,
3.50–3.98 (m, 6H, O–CH2)*, 4.22 (d, 1H, 3JHH = 11 Hz, CH), 7.32–7.69
(19H, m, aromatic)*, 10.08 (1H, s, N–H). 13C NMR (d6-DMSO, 100
MHz): δ 13.4, 13.6, 13.7, 14.0, 14.1 (3 CH3)*, 15.0 (CH3–CN), 20.9
5
6
7
1
2
(CH3), 42.6 (d, JPC = 60 Hz, C=P), 52.3 (d, JPC = 6 Hz, CH), 57.3,
59.9, 60.0, 60.6, 65.1, 65.7 (3 OCH2)*, 127.2 (d, 1JPC = 90 Hz, Cipso),
134.2 (d,3JPC = 10 Hz, Cmeta), 132.3 (d, 2JPC = 6 Hz, Cortho), 132.5 (Cpara),
128.0, 128.7, 129.3, 143.9 (NH-aromatic), 154.2 (C=N), 169.3 (C=O),
8
9
M. Anary-Abbasinejad, H. Anaraki-Ardakani and H. Hosseini-Mehdiabad,
Phosphorus, Sulfur Silicon Relat. Elem., 2008, 183, 1440.
2
1
170.3 (C=O), 174.2 (d, JPC = 5 Hz, C=O). Minor isomer (40%): H
NMR (CDCl3, 400 MHz): δ 0.88 (t, 3H, 3JHH = 7 Hz, CH3), 0.69–1.30
(m, 6H, 2 CH3)*, 1.54 (s, 3H, CH3), 2.33 (3H, s, CH3), 2.88 (1H, m,
10 H. Anaraki-Ardakani, S. Sadeghian, F. Rastegari, A. Hassanabadi and
M. Anary-Abbasinejad, Synth. Commun., 2008, 38, 1990.
11 M. Anary-Abbasinejad, H. Anaraki-Ardakani, A. Dehghan, A. Hassanabadi
and M.R. Seyedmir, J. Chem. Res., 2007, 574.
12 M.Anary-Abbasinejad, H.Anaraki-Ardakani,A. Ezadi andA. Hassanabadi,
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13 M.H. Mosslemin, M. Anary-Abbasinejad, A. Hassanabadi and M.A.
Bagheri, J. Sulfur, Chem., 2010, 31, 135.
CH)*, 3.50–3.98 (m, 6H, O–CH2)*, 4.20 (d, H, JHH = 11 Hz, CH),
7.32–7.69 (19H, m, aromatic)*, 10.02 (1H, s, N–H). 13C NMR
(d6-DMSO, 100 MHz): δ 13.4, 13.6, 13.7, 14.0, 14.1 (3 CH3)*, 15.4
1
3
1
2
(CH3–CN), 21.2 (CH3), 43.2 (d, JPC = 60 Hz, C=P), 52.1 (d, JPC
=
5 Hz, CH), 57.3, 59.9, 60.0, 60.6, 65.1, 65.7 (3 OCH2)*, 127.1 (d, 1JPC
14 J.C. Tebby, Phosphorus-31 NMR spectroscopy in stereochemical analysis,
J.C. Verkade, L.D. Quin eds. VCH, Weinheim, 1987, chap. 1, pp. 1–60.
15 E. Vedejs and K.A.J. Snoble, J. Am. Chem. Soc., 1973, 95, 5778.
3
2
= 91 Hz, Cipso), 134.4 (d, JPC = 10 Hz, Cmeta), 132.0 (d, JPC = 6 Hz,
ortho), 132.5 (Cpara), 128.4, 132.3, 133.0, 142.3 (NH-aromatic), 153.0
C

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