The insertion of dimethyl acetylenedicarboxylate into an S-Pd bond

Article abstract of DOI:10.1246/cl.2002.106

The first definitive evidence of insertion of an alkyne into an S-Pd bond has been presented. The reaction of Pd(SAr)₂(DPPE) with dimethyl acetylenedicarboxylate (DMAD) gave the cis-insertion product (Z)-Pd-[C(CO₂Me) = C(SAr)(CO

Full text of DOI:10.1246/cl.2002.106

106
Chemistry Letters 2002
The Insertion of Dimethyl Acetylenedicarboxylate into an S-Pd Bond
Kunihiko Sugoh, Hitoshi Kuniyasu,ꢀ and Hideo Kurosawaꢀ
Department of Applied Chemistry, Faculty of Engineering, Osaka University, Suita, Osaka 565-0871
(Received October 18, 2001; CL-011022)
The first definitive evidence of insertion of an alkyne into an
S-Pd bond has been presented. The reaction of Pd(SAr)2(DPPE)
hexane.12 Although efforts to obtain a high-quality crystal of 3a
were unsuccessful, a single X-ray crystallographic analysis of 3b
obtained by a similar procedure employing Pd(SAr)2(DPPE)
(Ar¼C6H4Cl-p) (1b) demonstrated that 3 was (Z)-Pd[CðEÞ ¼
CðEÞðSArފðSArÞðDPPEÞ (E ¼ CO2Me) (Figure 1).13 When the
isolated Z-3a was heated in C6D6 at 50 ꢁC, signals assignable to
with dimethyl acetylenedicarboxylate (DMAD) gave the cis-
insertion
product
CðSArÞðCO2MeފðSArÞðDPPEÞ, whose structure was unambigu-
(Z)-Pd-[CðCO2MeÞ ¼
ously determined by X-ray crystallographic analysis.
the E-isomer, whichwas different from 4a, appeared in 1H and 31
P
NMR spectra (E=Z ¼ 71=29 after 3 days).14 This result clearly
showed that IS of 2 into the S-Pd bond of 1a kinetically took place
in a cis-fashion.
With the discovery of the palladium-catalyzed cis-addition of
disulfides to alkynes as a trailblazing study,1a) a significant
number of reports on the transition metal-catalyzed additions of
RS-G to C-C unsaturated organic compounds have been
documented.1{7 For example, the palladium- or platinum-
catalyzed additions to alkynes giving cis-adducts have been
6
known when G are SR,1a) H,3a) BR2,4 P(O)(OAr)2,5 SiCl3 and
CO2Me.7 Although their reaction mechanisms still remain
unsettled, all reactions can be explained by a similar reaction
pathway: (1) RS-M (M¼Pd, Pt) bond formation; (2) cis-insertion
(IS) of alkynes into S-M bonds; (3) product formation with
regeneration of catalysts (Scheme 1).8 However, to the best of our
knowledge, no definitive evidence of IS of alkyne into S-M
(M¼Pd, Pt) bonds has been provided so far.9 We wish to report
here the first example of IS of alkyne into an S-Pd bond.10
Figure 1. ORTEP diagram of Z-3b (hy-
drogens and Ph group on DPPE omitted).
Scheme 1.
After 5.5 h of the reaction of 1a with 2, the yield of 4a (44%)
and 5(13%) increased, and a new pair of doublets(6a; ꢀ44.8and ꢀ
45.4 with JP-P ¼ 23 Hz, 16% yield) appeared. After 44 h, all such
doublet signals disappeared and the yield of 5 reached 80%.
Moreover, the compounds (ArS)(EC ¼ CE)n(SAr) 7 (n ¼ 1), 8
(n ¼ 2) were isolated by preparative TLC in 14% and 23% yield,
respectively15 and the mass spectra of other fractions showed
fragment peaks of 549 and 691 corresponding to (ArS)(EC ¼
CE)n (n ¼ 3, 4). The foregoing results suggested that the complex
3a underwent the successive IS of 2 into C-Pd bond of 3a,16 and
that organic moieties were reductively eliminated from Pd(II)
complexes.
When the reactions of 1b with excess amount of 2 in CD2Cl2
at 25 ꢁC were monitored by 31P NMR spectroscopy, the
disappearance rate of 1b obeyed first-order kinetics with respect
to the concentrations of 1b and 2.17 The pseudo-first-order rate
constants of disappearance of 1a–c (Ar¼Ph in 1c) measured using
0.016 M of 1 and 0.19 M of 2 showed that the electron-donating
group on Ar groups facilitated the IS of 2 (Table 1). This fact
First, the reaction of Pd(SAr)2(DPPE) (Ar¼C6H4Me-p,
DPPE ¼ 1,2-bisðdiphenylphosphinoÞethaneÞ (1a) (0.009 mmol)
with dimethyl acetylenedicarboxylate (DMAD) (2) (0.12 mmol)
in C6D6 (0.6 mL) at 25 ꢁC was monitored by 31P NMR
spectroscopy. The chart taken after 40 min showed that a couple
of doublets centered at ꢀ 41.4 and ꢀ 48.4 with JP-P ¼ 25 Hz (3a)
appeared in 72% yield together with another set of doublets (4a; ꢀ
44.8 and ꢀ 45.4 with JP-P ¼ 23 Hz, 13% yield) and a singlet of the
complex Pd0(DMAD)(DPPE) 511 (ꢀ 45.9, 2% yield) (eq 1). From
the reaction using 0.7 mmol of 1a, the compound 3a was isolated
in 46% yield as a yellow solid by recrystallization from benzene/
Copyright Ó 2002 The Chemical Society of Japan

Chemistry Letters 2002
107
Table 1. Pseudo-first-order rate constants for the IS of 2 into the
S-Pd bond of 1a
Soc., Dalton Trans., 1975, 2283. For Fe, see: f) W. Imhof and
G. Huttner, J. Organomet. Chem., 447, 31 (1993). g) F. Y.
Petillon, F. L. Floch-Perennou, and J. E. Guerchais, J.
Organomet. Chem., 173, 89 (1979).
1
kobs/sÀ1
1a; Ar¼C6H4Me-p
1c; Ar¼Ph
1:37 Â 10À3
6:52 Â 10À4
2:04 Â 10À4
10 For the IS of isocyanide into S-M bonds, see: H. Kuniyasu, K.
Sugoh, S. Moon, and H. Kurosawa, J. Am. Chem. Soc., 119,
4669 (1997).
1b; Ar¼C6H4Cl-p
aKinetic measurements were conducted in CD2Cl2 at 25 ꢁC.
Initial concentrations are ½1Š ¼ 0:016 M and ½2Š ¼ 0:19 M.
11 R. S. Paonessa, A. L. Prignano, and W. C. Trogler, Organo-
metallics, 4, 647 (1985).
12 3a: yellow solid (two molecules of benzene per molecule of
1
3a were incorporated in the crystal); mp 124 ꢁC; H NMR
indicated that nucleophilic character of SAr group stabilized the
transition state of the IS of 2 into an S-Pd bond.
(270 MHz, CD2Cl2) ꢀ 1.62–1.80 (br, m, 1 H), 2.10 (s, 3 H),
2.11–2.43 (br, m, 2 H), 2.24 (s, 3 H), 2.46–2.60 (br, m, 1 H),
3.30 (s, 3 H), 3.31 (s, 3 H), 6.46 (d, J ¼ 8:2 Hz, 2 H), 6.66 (d,
J ¼ 8:2 Hz, 2 H), 6.90 (d, J ¼ 8:1 Hz, 2 H), 6.99 (d,
J ¼ 8:1 Hz, 2 H), 7.18–7.60 (m, 26 H), 7.63–7.70 (m, 2 H),
7.76–7.83 (m, 2 H), 8.00–8.07 (m, 2 H); 31P NMR (109 MHz,
CD2Cl2) ꢀ 44.1 (d, JP-P ¼ 23 Hz), 49.4 (d, JP-P ¼ 23 Hz); IR
(KBr) 3457, 3051, 2941, 1723, 1708, 1686, 1543, 1484, 1433,
In summary, the first example of IS of alkyne into an S-Pd
bond has been reported. The secret of success to observe the vinyl
thiolato palladium would be attributable to the utilization of
DMAD as an alkyne. Further studies on the details of IS into S-M
bonds (M¼Pd, Pt) using various ligands and alkynes are now
under investigation.
1222, 1103, 1016, 874, 809, 746, 692, 680, 528, 492 cmÀ1
;
References and Notes
Anal. Calcd for C58H56O4P2PdS2: C, 66.37; H, 5.38; S,
6.11%. Found: C, 66.08; H, 5.41; S, 6.07%.
13 Crystal data for 3b: C56H50Cl2O4P2PdS2 (two molecules of
1
a) H. Kuniyasu, A. Ogawa, S. Miyazaki, I. Ryu, N. Kambe,
and N. Sonoda, J. Am. Chem. Soc., 113, 9796 (1991). b) T.
Kondo, S. Uenoyama, K. Fujita, and T. Mitsudo, J. Am. Chem.
Soc., 121, 482 (1999).
a) T. Kondo and T. Mitsudo, Chem. Rev., 100, 3205 (2000). b)
L. Han and M. Tanaka, J. Chem. Soc., Chem. Commun., 1999,
395.
a) H. Kuniyasu, A. Ogawa, K. Sato, I. Ryu, N. Kambe, and N.
Sonoda, J. Am. Chem. Soc., 114, 5902 (1992). b) A. Ogawa,
M. Takeba, J. Kawakami, I. Ryu, N. Kambe, and N. Sonoda, J.
Am. Chem. Soc., 117, 7564 (1995). c) A. Ogawa, J.
Kawakami, M. Mihara, T. Ikeda, N. Sonoda, and T. Hirao,
J. Am. Chem. Soc., 119, 12380 (1997).
T. Ishiyama, K. Nishijima, N. Miyaura, and A. Suzuki, J. Am.
Chem. Soc., 115, 7219 (1993).
L. Han and M. Tanaka, Chem. Lett., 1999, 863.
L. Han and M. Tanaka, J. Am. Chem. Soc., 120, 8249 (1998).
R. Hua, H. Takeda, S. Onozawa, Y. Abe, and M. Tanaka, J.
Am. Chem. Soc., 123, 2899 (2001).
An alternative pathway: (1) G-M bond formation; (2) cis-IS of
alkynes into M-G bonds; and (3) vinylC-S bond-forming
reductive elimination with regeneration of catalysts is also
possible for all reactions.
The ISs of alkynes into S-M have been reported with other
metals. For Ru, see: a) U. Koelle, C. Rietmann, J. Tjoe, T.
Wagner, and U. Englert, Organometallics, 14, 703 (1995).
For Rh, see: b) Y. Wakatsuki, H. Yamazaki, and H. Iwasaki, J.
Am. Chem. Soc., 95, 5781 (1973). For Mo, see: c) T. R.
Halbert, W. H. Pan, and E. I. Stiefel, J. Am. Chem. Soc., 105,
5476 (1983). For W, see: d) L. Carlton, W. A. W. A. Bakar,
and J. L. Davidson, J. Organomet. Chem., 394, 177 (1990).
For Co, see: e) J. L. Davidson and D. W. A. Sharp, J. Chem.
benzene per molecule of 3b were incorporated in the crystal),
ꢀ
Mw ¼ 1090:38, monoclinic, P21=n(#14), a ¼ 10:2ð1Þ A, b ¼
2
3
ꢁ
ꢀ
ꢀ
ꢀ 3
20:92ð8Þ A, c ¼ 24:27ð7Þ A, ꢁ ¼ 98:6ð5Þ , V ¼ 5098ð65Þ A ,
Z ¼ 4, Dcalcd ¼ 1:421 g/cm3, T ¼ 296 K, Mo Kꢂ, A total of
13093 reflections were measured in which 12420 were
independent (Rint ¼ 0:043). R ¼ 0:078, and Rw ¼ 0:084 for
6566 reflections with I > 3ꢃðIÞ.
14 E-3a: 1H NMR (270 MHz, C6D6) ꢀ 2.04 (s, 3 H), 2.15 (s, 3 H),
3.17 (s, 3 H), 3.44 (s, 3 H), 8.28–8.39 (m, 2 H) (the other peaks
were not assigned because of overlapping with the peaks of Z-
isomer); 31P NMR (109 MHz, C6D6) ꢀ 42.5 (d, JP-P ¼ 26 Hz),
51.5 (d, JP-P ¼ 26 Hz).
4
1
15 7: H NMR (270 MHz, C6D6) ꢀ 1.92 (s, 6 H), 3.16 (s, 6 H),
5
6
7
6.75 (d, J ¼ 8:1 Hz, 4 H), 7.38 (d, J ¼ 8:1 Hz, 4 H); mass
spectrum (EI) m/e 388 (Mþ, 13). HRMS Calcd for
C20H20O4S2 388.0803. Found 388.0802. 8: 1H NMR
(270 MHz, C6D6) ꢀ 1.89 (s, 6 H), 3.26 (s, 6 H), 3.40 (s, 6 H),
6.73 (d, J ¼ 8:4 Hz, 4 H), 7.54 (d, J ¼ 8:4 Hz, 4 H); mass
spectrum (EI) m/e 407 ((M-SAr)þ, 100).
8
16 The complexes 4a and 6a can be tentatively assigned to be
Pd[(EC ¼ CE)n(SAr)](SAr)(DPPE) (n ¼ 2 and 3), respec-
tively. For multiple insertion of DMAD into C-Pd bond, see:
T. Yagyu, K. Osakada, and M. Brookhart, Organometallics,
19, 2125 (2000).
9
17 The kinetic measurement was performed using 0.016 M of 1b.
The initial concentrations of 2 and pseudo-first-order rate
constants of 1b were as follows; 0.19 M, 2:04 Â 10À4 sÀ1
(shown in Table 1); 0.45 M, 4:72 Â 10À4 sÀ1; 0.82 M, 8:86Â
10À4 sÀ1; 1.10 M, 1:16 Â 10À3 sÀ1
.