Transformation of alkynyl sulfones into alkynylphosphonates with trialkyl phosphites

Article abstract of DOI:10.1016/j.tetlet.2008.02.013

1-Alkynylphosphonates were obtained in good to high yields by simple heating of 1-alkynyl sulfones with trialkyl phosphites.

Full text of DOI:10.1016/j.tetlet.2008.02.013

Available online at www.sciencedirect.com
Tetrahedron Letters 49 (2008) 2265–2267
Transformation of alkynyl sulfones into alkynylphosphonates
with trialkyl phosphites
Yasutaka Yatsumonji, Akitoshi Ogata, Akira Tsubouchi, Takeshi Takeda *
Department of Applied Chemistry, Graduate School of Engineering, Tokyo University of Agriculture and Technology, Koganei, Tokyo 184-8588, Japan
Received 9 January 2008; revised 1 February 2008; accepted 5 February 2008
Available online 8 February 2008
Abstract
1-Alkynylphosphonates were obtained in good to high yields by simple heating of 1-alkynyl sulfones with trialkyl phosphites.
Ó 2008 Elsevier Ltd. All rights reserved.
Keywords: Alkynylphosphonates; Alkynyl sulfones; Trialkyl phosphites; Arbuzov collapse
Dialkyl 1-alkynylphosphonates are useful synthetic
intermediates as acetonyl equivalents,1 Michael acceptors,2
components of [2+2]3 and [2+2+2]4 cycloadditions and
starting materials for certain cyclic compounds.5 Two
major approaches to these organophosphorous com-
pounds have been investigated;6 one is the reaction of alky-
nylmetals with electrophilic phosphorous reagents such as
dialkyl chlorophosphates and the other is the nucleophilic
displacement of alkynyl halides or related compounds with
phosphorous nucleophiles such as trialkyl phosphites and
sodium diethyl phosphite. Although the latter approach
is advantageous over the former in that it requires no
strongly basic reagents such as the Grignard reagents7 or
alkyllithiums,8 its utility is largely restricted. For example,
the nucleophilic displacement of 1-haloalkynes9 with trial-
kyl phosphites suffers the limitation that only a-haloacetyl-
enes bearing an electron-withdrawing or accommodating
group can be employed. This limitation has been partially
alleviated by the use of NiCl2 as a catalyst.10 1-Alkynyl-
phenyliodonium salts11 are good alternatives for 1-halo-
alkynes but these starting materials are not easily
accessible. Although the treatment of bromoalkynes with
sodium dialkyl phosphites at low temperature affords
alkynylphosphonates, it is pointed out that the purity of
the products becomes a serious problem in certain cases.6
In connection with our study on the titanocene(II)-
promoted cross-coupling of alkynes with unsaturated
compounds,12 we required a practical method for the
preparation of various dialkyl 1-alkynylphosphonates.
We then investigated a new method for their preparation
without the difficulties associated with the use of halo-
alkynes or chlorophosphates. We took particular note of
alkynyl sulfones as starting materials because these organo-
sulfur compounds are readily available from terminal
alkynes by simple procedures.
According to the method reported by Bieber,13 alkynyl
sulfides were prepared by the copper(I) iodide-catalyzed
reaction of terminal alkynes with diphenyl disulfide in
excellent yields. Oxidation of alkynyl phenyl sulfides with
m-chloroperbenzoic acid produced alkynyl sulfones 1
quantitatively.14 Treatment of phenyl 2-phenylethynyl sul-
fone (1a) with an equimolar amount of trimethyl phosphite
(2a) at 60 °C for 3 h produced alkynylphosphonate 3a in a
high yield (Scheme 1, Table 1, entry 1). Although the
O
R1
SO2Ph
R1
P(OR2)2
P(OR2)3
+
- R2SO2Ph
2
3
1
THF, 60 °C, 3 h
*
Corresponding author. Tel./fax: +81 42 388 7034.
Scheme 1.
E-mail address: takeda-t@cc.tuat.ac.jp (T. Takeda).
0040-4039/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetlet.2008.02.013

2266
Y. Yatsumonji et al. / Tetrahedron Letters 49 (2008) 2265–2267
Table 1
Preparation of 1-alkynylphosphonates 3
Entry
1
Alkynyl sulfone 1
Trialkyl phosphite 2
1-Alkynylphosphonate 3 (yield, %)a
SO2Ph
P(O)(OMe)2
1a
P(OMe)3 2a
3a (96)
Ph
Ph
P(O)(OEt)2
2
3
1a
1a
P(OEt)3 2b
3b (98)
Ph
P(O)(OiPr)2
P(OiPr)3 2c
3c (71)
Ph
SO2Ph
P(O)(OMe)2
4
1b
2a
2b
2c
2a
2b
2c
2a
2b
2c
3d (93)
Ph
Ph
P(O)(OEt)2
5
1b
3e (90, 88b)
Ph
P(O)(OiPr)2
6
1b
3f (70)
Ph
SO2Ph
P(O)(OMe)2
7
1c
3g (90)
Hex
Hex
P(O)(OEt)2
8
1c
3h (95)
Hex
P(O)(OiPr)2
9
1c
3i (71)
Hex
SO2Ph
P(O)(OMe)2
10
11
1d
3j (90)
P(O)(OEt)2
1d
1d
3k (95)
P(O)(OiPr)2
12
3l (70)
a
Isolated yield.
b
The reaction was carried out in 20 mmol scale and 3e was isolated by distillation (170–175 °C/0.5 mmHg).
similar treatment of 1a with triethyl phosphite (2b) gave
phosphonate 3b quantitatively (entry 2), the reaction using
more bulky triisopropyl phosphite (2c) gave 3c in a lower
yield (entry 3). In a similar fashion, various 1-alkynyl-
phosphonates 3 were obtained by the reaction of alkynyl
phenyl sulfones 1 with trialkyl phosphites 2 in good to high
yields.15
The preparation of alkynylphosphonates using alkynyl-
phenyliodonium tosylates or 1-haloalkynes requires the use
of excess phosphites and these starting materials are either
rather unstable or explosive.16 The present reaction enjoys
advantages over these conventional methods in that the
phosphonates are obtained in good to high yields using
equimolar amounts of phosphites without aqueous
workup. Indeed, phosphonate 3e was obtained in a yield
comparable to that obtained by a small scale reaction even
when the reaction was carried out in gram scale and 3e was
isolated by the concentration of the reaction mixture and
the distillation of the residue (entry 5).
Three reaction pathways have been proposed for the
formation of 1-alkynylphosphonates by the reaction of
alkynes having a leaving group (X) with phosphites
(Scheme 2);6 the formation of phosphonium salts with an
acetylide counterion 4 by nucleophilic attack of phosphites
to the leaving group (Path A), the addition of phosphites to
the alkynes to form the twitter ions 5 (Path B) and the
Michael-type addition of phosphites to the alkynes
followed by the elimination of the leaving group to form
alkylidenecarbenes 6 (Path C). The final step of all these
pathways is the Arbuzov collapse of alkynylphosphonium
salts 7. Considering the strong electron-withdrawing and
poor leaving abilities of phenylsulfonyl group, it is reason-
able to assume that the present reaction follows Path C via
the carbene intermediates 6.

Y. Yatsumonji et al. / Tetrahedron Letters 49 (2008) 2265–2267
2267
Path A
X
P(OR2)3
R1
R1
C
C
4
R1
C
C
P(OR2)3
X
3
+
R2X
R1
C
C
2
+
X
P(OR2)3
X
7
C
C
Path C
5
Path B
R1
C
(R2O)3P
R1
C
X
C C
(R2O)3P
X
6
Scheme 2.
8. Gil, J. M.; Sung, J. W.; Park, C. P.; Oh, D. Y. Synth. Commun. 1997,
27, 3171.
Acknowledgements
9. For the pioneering work on the synthesis of 1-alkynylphosphonates
by the reaction of haloalkynes with phosphites, see: Ionin, B. I.;
Petrov, A. A. Zhur. Obshch. Khim. 1962, 32, 2387.
This work was supported by Grant-in-Aid for Scientific
Research (No. 18350018) and Grant-in-Aid for Scientific
Research on Priority Areas ‘Advanced Molecular Trans-
formations of Carbon Resources’ (No. 19020016) from
the Ministry of Education, Culture, Sports, Science and
Technology, Japan.
10. Ha¨gele, G.; Goudetsidis, S.; Wilke, E.; Seega, J.; Blum, H.; Murray,
M. Phosphorus Sulfur Silicon Relat. Elem. 1990, 48, 131.
11. Lodaya, J. S.; Koser, G. F. J. Org. Chem. 1990, 55, 1513.
12. (a) Ogata, A.; Nemoto, M.; Kobayashi, K.; Tsubouchi, A.; Takeda,
T. Eur. J. Org. Chem. 2006, 878; (b) Ogata, A.; Nemoto, M.;
Kobayashi, K.; Tsubouchi, A.; Takeda, T. Chem. Eur. J. 2007, 13,
1320; (c) Ogata, A.; Nemoto, M.; Kobayashi, K.; Tsubouchi, A.;
Takeda, T. J. Org. Chem. 2007, 72, 3816.
References and notes
13. Bieber, L. W.; da Silva, M. F.; Menezes, P. H. Tetrahedron Lett. 2004,
45, 2735.
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E. J.; Virgil, S. C. J. Am. Chem. Soc. 1990, 112, 6429; (c) Guile, S. D.;
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2. (a) Cristau, H.-J.; Mbianda, X. Y.; Beziat, Y.; Gasc, M.-B. J.
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14. Truce, W. E.; Brady, D. G. J. Org. Chem. 1966, 31, 3543.
15. The typical procedure is as follows: A THF (4 mL) solution of phenyl
4-phenyl-1-butynyl sulfone 1b (540 mg, 2 mmol) and trimethyl phos-
phite 2a (0.24 mL, 2 mmol) was heated at 60 °C for 3 h under argon.
After cooling, the reaction mixture was concentrated. Chromato-
graphy of the residual oil on a silica gel (hexane–AcOEt = 2:1, v/v)
gave dimethyl 4-phenyl-1-butynylphosphonate 3d (443 mg, 93%) and
methyl phenyl sulfone (248 mg, 73%). Compound 3d: 1H NMR d 2.66
(dt, J = 4.4, 7.3 Hz, 2H), 2.90 (t, J = 7.4 Hz, 2H), 3.70 (d,
J = 12.3 Hz, 6H), 7.18–7.35 (m, 5H); 13C NMR d 21.1, 21.2, 33.39,
33.41, 53.0, 53.1, 67.7, 71.7, 102.4, 103.1, 126.6, 128.2, 128.4, 139.1;
31P NMR d À2.7; IR (neat) 2931, 2857, 2204, 1459, 1276, 1184, 1033,
837, 783, 627 cmÀ1. Anal. Calcd for C12H15O3P: C, 60.50; H, 6.35.
Found: C, 60.73; H, 6.66.
6. For a review, see: Iorga, B.; Eymery, F.; Carmichael, D.; Savignac, P.
Eur. J. Org. Chem. 2000, 3103.
7. Chattha, M. S.; Aguiar, A. M. J. Org. Chem. 1971, 36, 2719.
16. Miller, S. I.; Ziegler, G. R.; Wieleseck, R. Org. Synth. 1973, Coll. Vol.
V, 315.