Stereoselective addition of sodium organyl chalcogenolates to alkynylphosphonates: Synthesis of diethyl 2-(organyl)-2- (organochalcogenyl)vinylphosphonates

Article abstract of DOI:10.1016/S0040-4039(99)02044-4

Organyl thiolate, selenolate or tellurolate anions reacted with alkynylphosphonates 1 to give diethyl 2-(organyl)2- (organochalcogenyl)vinylphosphonates [β-organochalcogenyl vinylphosphonates] 2 in satisfactory yields. The reaction was stereoselective, gi

Full text of DOI:10.1016/S0040-4039(99)02044-4

TETRAHEDRON
LETTERS
Pergamon
Tetrahedron Letters 41 (2000) 161–163
Stereoselective addition of sodium organyl chalcogenolates to
alkynylphosphonates: synthesis of diethyl
2-(organyl)-2-(organochalcogenyl)vinylphosphonates
Antonio L. Braga,∗ Elenilson F. Alves, Claudio C. Silveira and Leandro H. de Andrade
Departamento de Química, Universidade Federal de Santa Maria, 97105-900, Santa Maria, RS, Brazil
Received 30 July 1999; revised 20 October 1999; accepted 21 October 1999
Abstract
Organyl thiolate, selenolate or tellurolate anions reacted with alkynylphosphonates 1 to give diethyl 2-(organyl)-
2-(organochalcogenyl)vinylphosphonates [β-organochalcogenyl vinylphosphonates] 2 in satisfactory yields. The
reaction was stereoselective, giving predominantly or exclusively the (Z)-stereoisomer. © 1999 Elsevier Science
Ltd. All rights reserved.
In the last few decades, there has been remarkable interest in the synthesis of vinylic chalcoge-
nides and their synthetic applications.1a Diethyl 2-(organyl)-2-(organochalcogenyl)vinylphosphonates
[β-organochalcogenyl vinylphosphonates] 2 are intermediates of great synthetic potential since they
combine the well-known chemical reactivity of vinylic chalcogenides1a and vinylic phosphonates.1b The
selenium derivatives were recently prepared by Pd-mediated stereoselective selenophosphorylation of
alkynes.2
Hydrometallation of acetylenes is a widely used method for the synthesis of vinylic metal and
metalloid derivatives.1a In this communication we describe a new, general and stereoselective method
to synthesize β-organochalcogenyl vinylphosphonates 2 by means of the hydrochalcogenation of diethyl
1-alkynylphosphonates 1.
We started our investigations with the hydrotelluration of alkynylphosphonates.3 The reaction was
performed by addition of alkynylphosphonates to a solution of sodium organyl tellurolate, prepared by
reduction of diorganyl ditellurides with sodium borohydride in ethanol at room temperature4 (Scheme
1). The β-organotelluranyl vinylphosphonates were formed in satisfactory yields with total regio- and
Z-stereoselectivity (Table 1). The same procedure was used for the synthesis of β-organosulfanyl and
organoselanyl vinylphosphonates. However, in these cases, the stereoselectivity was lower than for the
tellurium analogues, probably as a result of the lower nucleophilicity of the organyl thiolate and selenolate
anion. In all cases studied, only the regioisomer shown in Scheme 1 was obtained. This result can be
∗
Corresponding author. E-mail: albraga@quimica.ufsm.br (A. L. Braga)
0040-4039/00/$ - see front matter © 1999 Elsevier Science Ltd. All rights reserved.
PII: S0040-4039(99)02044-4
tetl 15972

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rationalized in terms of a Michael-type addition with carbanion stabilization by the diethoxyphosphinyl
group.1b
Scheme 1.
Table 1
Preparation of diethyl 2-(organyl)-2-(organochalcogenyl)vinylphosphonates 2
The exclusive Z-stereochemistry was expected by analogy with the hydrotelluration of acetylenes.5
These configurations were confirmed by NMR spectral analysis, especially NOESY experiments, for all
the compounds 2.
In summary, a novel method for the synthesis of diethyl 2-(organyl)-2-(organochalcogenyl)vinylphos-
phonates 2 has been established. It is expected that the reactions described above will find considerable
application in organic synthesis.
Acknowledgements
The authors thank the following agencies for support: CNPq, CAPES, DAAD and FAPERGS.
References
1. For reviews on the synthetic utility of vinylic selenides/tellurides and vinylic phosphonates, see: (a) Comasseto, J. V.; Ling,
L. W.; Stefani, H. A.; Petragnani, N. Synthesis 1997, 373. (b) Minami, T.; Motoyoshiya, J. Synthesis 1992, 333.
2. Tanaka, M.; Choi, N.; Han, L. J. Am. Chem. Soc. 1996, 118, 7000.
3. Oh, D. Y.; Gil, J. M.; Sung, J. W.; Park, C. P. Synth. Commun. 1997, 27, 3171.
4. Typical procedure: To a solution of RYNa [generated in situ from R2YYR2 (1.0 mmol) and NaBH4 (2.2 mmol)] in absolute
ethanol (10 mL) the 1-alkynylphosphonate 1 (2.0 mmol) was added dropwise at room temperature. The reaction mixture was

163
stirred for the time indicated in Table 1. Then the mixture was poured into a saturated aqueous solution of NH4Cl (10 mL)
and the aqueous layer was extracted with ethyl acetate (2×25 mL). The organic layer was dried (MgSO4) and evaporated. The
residue was purified by flash chromatography on silica gel with ethyl acetate:hexane (3:7). Selected spectral and analytical
1
data for 2 (R2Y=PhTe; R1=n-Bu): H NMR (200 MHz, CDCl3): δ 7.92 (d, J=7.6 Hz, 2H), 7.42–7.21 (m, 3H), 6.27 (d,
2JP–H=16.4 Hz, 1H), 4.11 (dq, 3JP–H=7.5 Hz, J=7.2 Hz, 4H), 2.21 (t, J=7.8 Hz, 2H), 1.40–1.23 (m, 2H), 1.35 (t, J=7.2 Hz,
6H), 1.00 (sext, J=7.4 Hz, 2H), 0.66 (t, J=7 Hz, 3H); 13C NMR (50 MHz, CDCl3) δ 154.75 (d, 2JP–C=6.3 Hz), 141.43, 128.58,
128.27, 115.33 (d, 1JP–C=192 Hz), 115.29, 61.27 (d, 2JP–C=5 Hz), 41.67 (d, 3JP–C=23 Hz), 31.56, 21.16, 15.94 (d, 3JP–C=6.2
Hz), 13.05; 31P NMR (161 MHz, CDCl3) δ 15.33 (s); MS m/z (relative intensity) 426 (M+2, 25), 347 (15), 219 (76), 163 (80),
81 (100); IR (KBr, film; cm-1) 3064, 2956, 1559, 1433, 1391, 1292, 1231, 1163, 1027, 965. Anal. calcd for C16H25O3PTe: C,
45.33; H, 5.94. Found: C, 44.91; H, 5.80.
5. Barros, S. M.; Dabdoub, M. J.; Dabdoub, V. M. B.; Comasseto, J. V. Organometallics 1989, 8, 1661.