MAGNETIC RESONANCE IN CHEMISTRY
Magn. Reson. Chem. 2007; 45: 87–89
Published online 2 November 2006 in Wiley InterScience
Spectral Assignments and Reference Data
1
Complete assignment of H and 13C NMR
O
3
H3C
2
spectra of some a-arylthio and a-arylsulfonyl
substituted N-methoxy-N-methyl
OCH3
4
N
5
propionamides
7
SOn
CH3
1
8
Nelson L. C. Domingues,1 Mirta G. Mondino,2
Adriana K. C. A. Reis,3 Roberto Rittner,3 Filipe S. Lima1 and
6
11
9
Paulo R. Olivato1∗
Y
12
10
1
Conformational Analysis and Electronic Interactions Laboratory, Insti-
tuto de Quımica, USP, Caixa Postal 26077, 05513-970 Sao Paulo, Sao
n = 0
n = 2
´
˜
˜
Paulo, Brazil
1 Y = MeO
2 Y = Me
3 Y = H
6 Y = MeO
7 Y = Me
8 Y = H
2
F.C.F.B.-Faculdades Oswaldo Cruz, 01151-000, Sa˜ o Paulo, Brazil
Physical Organic Chemistry Laboratory, Chemistry Institute, State
3
University of Campinas, Caixa Postal 6154, 13084-971 Campinas, Sa˜ o
Paulo, Brazil
4 Y = Cl
9 Y = Cl
5 Y = NO2
10 Y = NO2
Received 3 August 2006; revised 5 September 2006; accepted 29 September
2006
Scheme 1. Structures and numbering for compounds 1–10.
The complete assignments of the 1H and 13C NMR spectra
of the some a-arylthio and a-arylsulfonyl substituted
N-methoxy-N-methyl propionamides, bearing methoxy,
methyl, chloro, and nitro as substituents at the phenyl
ring are reported. Copyright 2006 John Wiley & Sons,
Ltd.
bicarbonate. These compounds were obtained in 85–97% yield.
Elemental analyses were carried out on a Perkin-Elmer 2400 CHN-
standard analyzer (Table 1).
Spectra
1H NMR and 13C NMR spectra were recorded on a Varian Inova 300
spectrometer (10% in CDCl3 solutions) operating at 299.947 MHz
and 75.423 MHz, respectively. Data processing was carried out on a
Solaris workstation.
KEYWORDS: NMR; 1H NMR; 13C NMR; N-methyl propionamides
1H NMR parameters were as follows: spectral width, 4000 Hz;
°
data points, 32K, zero-filled to 64K; pulse width 45 , acquisition
time, 4.10 s; digital resolution, 0.25 Hz. 13C NMR parameters were
INTRODUCTION
as follows: spectral width, 18 860 Hz; data points, 64K, zero-filled
N-methoxy-N-methylamides1 (commonly named Weinreb amides)
are important carboxylic acid derivatives that have been widely
used for the preparation of ketones, whose synthetic utility has
been extensively demonstrated.2–4 The efficiency of the reaction
involving these compounds has been attributed to the formation of an
intermediate stable tetrahedral lithium chelate,5 which precludes the
second nucleophilic addition to the carbonyl group. This important
characteristic of the chelate allowed us to synthesize some ketone
derivatives of ˇ-lactams in good yields, which had not been
possible through traditional methods employing other carboxylic
acid derivatives.6
°
to 128 K; pulse width 90 ; acquisition time, 1.76 s; digital resolution,
0.57 Hz, with a delay of 2.05 s between transients.
1H and 13C chemical shifts are given on the υ scale (ppm) and
were referenced to TMS, and coupling constants J are reported in
Hz. The following abbreviations were used: s, d, q and m, for singlet,
doublet, quartet and multiplet, respectively.
RESULTS AND DISCUSSION
As a first step, the 1H NMR spectra of compounds 3 and 8 (Y D H)
were fully assigned and are in agreement with literature data.8
The remaining compounds were then assigned by analogy. For
compounds 1–10, the doublet signal at υ ¾ 1.4–1.6 ppm corresponds
to the H-3 methyl group, attached to the chiral carbon (C-5),
with a coupling constant of ¾7.0 Hz. (Table 2). The singlets at
υ ¾ 3.2 ppm and υ ¾ 3.6–3.8 ppm correspond to H-1 and H-2
methyl groups, respectively, and the quartet at υ ¾ 4.1–4.8 ppm
to the H-5 methine group, which has the chiral carbon (C-5). The
low-frequency multiplet signals at υ 6.8–9.0 ppm were identified as
the aromatic protons chemical shifts.
The aim of this work was to prepare some 40-substituted
N-methoxy-N-methyl-2-phenylthio- and 40-substituted N-methoxy-
N-methyl-2-phenylsulfonyl-propionamides (Scheme 1) and to char-
acterize them through their 1H NMR and 13C NMR spectra.
EXPERIMENTAL
Compounds
The mild acylating agents 40-substituted N-methoxy-N-methyl-2-
phenylthio-propionamides are easy to prepare and are very stable
for a long time.
The 13C NMR chemical shifts are presented in Table 3. The
signals at υ ¾ 32 ppm and at υ ¾ 61 ppm, for the whole series,
Initially, the 40-substituted 2-phenylthiopropionic acids were
obtained from the reaction of 2-bromopropionic acid with an
aqueous solution of 4-substituted thiophenols and two equiva-
lents of sodium hydroxide.7 These acids were converted to the
corresponding acyl chlorides, which led to the 40-substituted N-
methoxy-N-methyl-2-phenylthiopropionamides by their reaction
with N,O-dimethylhydroxylamine hydrochloride.
correspond to C-1 and C-2, respectively. The deshielding for the
¾
chiral carbon C-5 (υ
60 ppm) in compounds 6–10, in relation to
D
¾
1–5 (υ 41 ppm), may be ascribed to the larger inductive effect of
D
the arylsulfonyl group (ꢀI D C0.56),9 in comparison to the arylthio
group (ꢀI D C0.31).9 The inverse effect was observed for the C-3
methyl carbon attached to the chiral carbon and for the C-4 carbonyl
carbon, where the corresponding shifts are deshielded in compounds
¾
¾
D
1–5 (υ 17 ppm and υ 173 ppm, respectively), in relation to 6–10
D
The obtained amides were oxidized to the corresponding
sulfones using oxone [potassium peroxymonosulfate (2KHSO5.
KHSO4.K2SO4)] in acetone solution and five equivalents of sodium
¾
¾
D
(υ 13 ppm and υ 166 ppm, respectively).
D
The C-6 and C-9 aromatic carbons at
υ
¾
120–140 and
υ ¾ 130–160 ppm, respectively, were largely dependent on the
substituent in the aryl group, as expected, while less pronounced
effects were observed for C-7/C-11 and C-8/C-10 chemical shifts,
which are in agreement with reported values.10
Ł
´
Correspondence to: Paulo R. Olivato, Instituto de Quımica – USP, Caixa
Postal 26077, 05513-970 Sa˜o Paulo, SP, Brazil. E-mail: prolivat@iq.usp.br
Copyright 2006 John Wiley & Sons, Ltd.
Domingues, Nelson L. C.
