J. Org. Chem. 1996,60, 74-83
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Synthesis, Molecular Structure, and Spectroscopical Properties of Alkenylphosphonic Derivatives. 1. Vinyl-, Propenyl-, (Bromoalkeny1)-,and (Cyanoalkeny1)phosphonic Compounds C. I. Sainz-Diaz,*tt E. Galvez-Ruano,* A. Herntindez-Laguna,",S and J. Bellanatol Instituto de Estructura de la Materia (CSIC), Serrano 123, 28006 Madrid, Spain, Dpt. Quimica Organica, Universidad de Alcalci de Henares, Alcala de Henares, Madrid, Spain, Instituto de Optica (CSIC), Serrano 121, 28006 Madrid, Spain, and Estacibn Experimental del Zaidin (CSIC), Prof Albareda 1,18008-Granada, Spain Received March 31, 1994@
Several vinyl-, propenyl-, (bromoalkeny1)-, and (cyanoalkeny1)phosphonate derivatives have been synthesized. The (2-cyanoviny1)phosphonateshave been obtained with an important improvement in the yield (40% versus 6%). The separation of the E and Z isomers of the cyano derivatives and their hydrolysis to the corresponding phosphonic acids have been studied. The bromination and dehydrobromination of some alkenylphosphonic derivatives have also been studied. Spectroscopical studies from W, IR, Raman, and lH, 13C, and 31PNMR have been performed in most of these derivatives. The C=C/P=O n conjugation exists but it is weak in all these compounds. Dipole moments and C=C/P=O conformational populations have been calculated theoretically by a b initio methods. The effect of the solvent polarity on the conformational population has been observed by IR spectroscopy disclosing two C=C/P=O conformers. Experimental and theoretical results have been compared, a high level of agreement has been found.
Introduction Phosphonates are compounds of broad use and interest in chemistry, pharmacology, and industry, such as Wittig-Horner-Emmons reactives, as analogues of natural phosphates,l drug^,^-^ and herbicide^,^ polymer additives,6 selective extractants of metal,7 flame retards,8 etc. In nature, some phosphonates have been isolated from a certain number of microorganisms.' However, there are very few references about molecular structure and spectroscopical properties of these compounds. In earlier papers, preliminary studies about the structure of alkenylphosphonic derivatives have been performed by means of NMR, IR, and W spectroscopy and a b initio c a l c ~ l a t i o n s . ~ These - ~ ~ compounds are presented a s very polar, especially as far as the phosphoryl bond is concerned. This bond is a partially polarized
* To whom correspondence should be addressed. Present address: Christian Doppler Laboratorium, Technische Universitat Graz, Inffeldgasse 25, A-8010 Graz, Austria. + Instituto de Estructura de la Materia. Universidad de Alcala de Henares. 8 Estacih Experimental del Zaidin. Instituto de Optica. Abstract published in Advance ACS Abstracts, December 1,1994. (1)Engel, R. Chem. Rev. 1977,77,349. (2)Smeyers, Y. G.; Hernandez-Laguna, A.; Von Carstenn-Lichterfelde, C. J . Pharm. Sci. 1983,72, 1011. (3)Smeyers, Y. G.; Hernandez-Laguna, A.; Romero-Sanchez, F. J.; Fernhdez-Ibaiiez, M.; GAlvez-Ruano,E.; Arias-Perez, M. S. J. Pharm. Sci. 1987,76, 753. (4)Hemmi, K.; Takeno, H.; Hashimoro, M.; Kamiya, T. Chem. Pharm. Bull. 1982,30, 111. (5) Eto, M. Organophosphorus pesticides. Organic and Biological Chemistry; CRC: Boca Raton, 1974; pp 329-67. (6) Zyablikova, T. A.; Il'yasov, A. V.; Mukhametzyanova, E. Kh.; Shersnergorn, I. M. J . Gen. Chem. USSR 1981,249. (7) Degenhart, C. R.; Burdsall, D. C. J. Org. Chem. 1986,51,3488. ( 8 )Welch, C. M.; Gonzales, E. J.; Guthrie, J. D. J . Org. Chem. 1961, 26, 3270. (9) Gblvez-Ruano, E.; Bellanato, J.; Fernlndez-Ibliiez, M.; SainzDiaz, C. I.; Arias-Perez, M. S. J . Mol. Struct. 1986,142, 397. (10)Smeyers, Y. G.; Hernandez-Laguna, A.; Fernandez-Ibaiiez, M.; Sainz-Diaz, C. I.; Galvez-Ruano, E.; Arias-Perez, M. S. J . Mol. Struct. 1988,174, 267. (11)Smeyers, Y. G.; Hernandez-Laguna, A.; Sainz-Diaz, C. I.; Fernandez-Ibbiiez, M.; Galvez-Ruano, E.; Arias-Perez, M. S. J . Mol. Struct. 1990,218,175.
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triple bond.12 Around the rotation of the C-P bond, two conformers s-cis and s-trans-gauche and two low internal rotation barriers were found, s-cis being the most stable in vinyl and trans-propenyl derivatives. In the case of cis-propenylphosphonic compounds the conformers are s-cis and s-trans with higher internal rotation bar14ers.l~ Synthesis of phosphonates can be performed following two different main pathways: (i) An haloalkenyl compound reacts with an alkyl phosphite yielding directly the alkenylphosphonate (Michaelis-Arbuzov's reaction), and (ii) the alkylphosphonate is obtained previously by Arbuzov's procedure and the alkenyl moiety is obtained by the usual methods of dehydrogenation, reduction, dehydrohalogenation, Wittig's reactions, etc. The second procedure gives higher yields, but a mixture of E and Z isomers is obtained. The hydrolysis of the phosphonates yields the corresponding phosphonic acids. On the other hand, in some of these compounds no reference on the ZIE rate study and separation yield of these EIZ isomers has been found in the bibliography. In a previous paper the synthesis procedure of the vinylphosphonic acid has been improved, increasing the yield to up to 90%,l2 by means of the formation of diethyl vinylphosphonate by Arbuzods reaction and the hydrolysis of this phosphonate by the McKenna et al. method14 modified by us. The interest and applications of the phosphonates have prompted us to study the synthesis methods with the aim of improving them and obtaining better yields, ZIE ratios, and isomer separations. With these compounds, a structural study by means of NMR, W, IR, and Raman spectroscopy and a b initio calculations has been performed with the purpose to gain a better insight into the molecular structures and elucidate their physicochemical properties and applications. Twenty-three vinyl-, pro(12)Hernandez-Laguna, A.; Sainz-Diaz, C. I.; Smeyers, Y. G.; de Paz, J. L. G.; Gblvez-Ruano, E. J.Phys. Chem. 1993,98, 1109-16. (13)Sainz-Diaz, C. I.; Hernhdez-Laguna, A,; Smeyers, N. J.; Smeyers, Y. G. THEOCHEM, in press. (14) McKenna, C. E.; Higa, M. T.; Chung, N. H.; McKenna, M. C. Tetrahedron Lett. 1977,15558.
0 1995 American Chemical Society
J . Org. Chem., Vol. 60, No. 1, 1995 76
Synthesis and Properties of Alkenylphosphonic Derivatives Table 1. Alkenylphosphonic Derivatives R4,
R3/c=c, compd
I I1 I11 Iv V VI VI1 VIII
M X XI XI1 XI11 XTV
xv
XVI XVII XVIII
XIX
xx xxl
R1 OH OEt OMe OEt OH OH OEt OtBut OtBut c1 OMe OMe OH 0OtBut OH
Rz
H,C=CHCN + Br,
,R5
R3
H H H H
OH
H
OH OEt OtBut OtBut c1 OMe OMe
Me Me Me
0OtBut
OH
OH OH
OEt c1 OtBut OEt OEt OH
OEt c1 OtBut OEt OEt OH
CH,Br- CHBr - CN
Base _3
CN 'C=C' + H' 'Br H
P(O)Rl R2
OH OEt OMe OEt
OH
4
H Me
H CN H H H
H Me H H
R4
H H Me Me Me H H H Me H CN H CN CN CHzBr Me
H
Rs H H H H H H H H H H H
Figure 1. Formation of (2-cyanoviny1)phosphonates. Table 2. Synthesis of Dimethyl (E/Z) (2-Cyanoviny1)phosphonates(xI/xII)
H
0 20 40 60
H H
H Br Br Br
H H Me CHz=C= H ethylphosphonate 2-propenylphosphonate 2-propenylphosphonic acid
a
uct.
40
10 4 4
