CONCLUSIONS

A new, simple and effective method was developed for the synthesis of difficultly ob- tainable bicyclic pyridine bases by the condensation of cyclic ethynylcarbinols with carbox- ylic acid anhydrides in the presence of an equimolar ZnCI 2-POCI 3 mixture followed by treat- ment with ammonium hydroxide.

I.

2.

3.

4.

5.

6.

7.

LITERATURE CITED

U. M. Dzhemilev, F. A. Selimov, V. F. Khafizov, et al., Sixth IUPAC International Con- ference of Organic Synthesis, Moscow (1986), p. 53. A. Balaben and A. Dinculescu, Advances in Heterocyclic Chemistry, Suppl. 2, Academic Press, New York (1982), pp. 1-31. G. N. Dorofeenko, E. I. Sadekova, and E. V. Kuznetsov, Preparative Chemistry of Pyrylium Compounds [in Russian], Izd. Rostov. Univ. (1972). G. N. Dorofeenko, Yu. A. Zhdanov, and L. N. Etmetchanko, Khim. Geterotsikl. Soedin. (1969), p. 781. F. A. Salimov, O. G. Rutman, and U. M. Dzhemilev, Izv. Akad. Nauk SSSR, Ser. Khim., 688 (1986). U. M. Dzhemilev, F. A. Selimov, O. G. Rutman, and A. Zh. Akhmetov, All-Union Conference on the Chemistry of Unsaturated Compounds. Abstracts [in Russian], Kazan' (1986), p. 130. B. J. Hazzard et al., Organicum: A Practical Handbook of Organic Chemistry, Pergamon Press, New York (1973).

SYNTHESIS OF PHOSPHONIUM 1,3,2,5-DIOXABORATAPHOSPHORINANES

G. N. Nikonov, A. A. Karasik, and O. A. Erastov

UDC 542.91:547.1'127' i18

Reactions of bis(=-hydroxyalkyl)phosphines or their oxides, sulfides, and selenides with asters of diphenylboric acid in the presence of tertiary, secondary, primary, and aromatic amines or ammonia yield 1,3,2,5-dioxaborataphosphorinanes [1-3], which display complex-salt tautomerism [i-5]. The presence of the ammonium cation in the structures of the compounds is responsible for the ease and unambiguity of the proceeding of reactions with eiectrophiles [6]. It seemed of interest to substitute the ammonium for a phosphonium cation. However, reaction of bis(hydroxymethyl)phenylphosphine with the isobutyl ester of diphenylboric acid in the presence of triphenylphosphine did not give phosphonium 1,3,2,5-dioxaborataphosphori- nane.

One of the tautomeric forms of ammonium 1,3,2,5-dioxaborataphosphorinanes consists of a salt structure for which an ion-exchange reaction is possible. Indeed, when ammonium 1,3,2,5 dioxaborataphosphorinanes were reacted with phosphonium salts in the two-phase system organic solvent-water the ion-exchange reaction took place and for the first time phosphonium 1,5,- 2,5-dioxaborataphosphorinanes (I) and (II) were isolated.

R [ CH--O

PhP / ~Pb.~. H--A ~- MePh3PI JI\ / O CH--O

B

R

CH--O /

PhP ~ B Ph2- Mol~Ph~ + - -

T H (1), ( II)

R = H (1), Ph (If); A = HNPr2 ([), NEt~ (If).

Derivatives (I) and (Ii) are crystalline compounds. In their IR spectra absorptions of hydroxyl and ammonium groups are not present~ In the 3Zp NMR spectra of these compounds there are two signals of equal intensity. In the PMR spectra of compound (I) the ratio of

A. E. Arbuzov Institute of Organic and Physical Chemistry, Academy of Sciences of the USSR, Kazan Branch. Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, Noo ii, pp. 2607-2609, November, 1988. Original article submitted July I, 1987o

0568-5230/88/3711-2349512.50 �9 1989 Plenum Publishing Corporation 2349

the integrated intensities of the phenyl, methyl, and methylene protons is 30:3:4. The sig- nals of the methyl and methylene protons are doublets with spin-spin coupling constants with Sip of 15 and 4 Hz, respectively. In the PMR spectra of compound (II) the ratio of the integrated intensities of the phenyl, methyl, and methine protons is 40:3:2. These data, together with the data of elemental analyses, unambiguously point to the isolation of methyl- (triphenyl)phosphonium 2,2,5-triphenyl- and 2,2,4,5,6-pentaphenyl-l,3,2,5-dioxaborataphos- phorinane oxides (I) and (If). From the water layer of the reaction mixture we isolated tri- ethylammonium iodide in a yield of 75%~

In addition to ammonium 1,3,2,5-dioxaborataphosphorinanes, also phosphorus-containing borates of alkali metals can undergo the ion-exchange reaction. Thus, from the reaction of sodium methoxy(diphenyl)borataoxybenzyl(hydroxybenzyl)phenylphosphine oxide with methyltri- phenylphosphonium iodide we isolated a crystalline product, in the PMR spectrum of which we observed three groups of signals corresponding with phenyl, methyl, and methylene protons in the ratio of 40:3:2; however, the spectrum of the compound is different from the spectrum of (II). The elemental analysis corresponds with methyltriphenylphosphonium 2,2,4,5,6-penta- phenyl-l,3,2,5-dioxaborataphosphorinane oxide. equal intensity.

Ph l CH--OH

/ PhP Ph

0 CH--OB--Ph Na + MePPh31 --Nal T \ Ph OMe

The sip NMR spectra contains two signals of

Ph 1

O CH--O Ph Li/ \_/ +

PhP B MePPh3

~CH--O / \ P h i Ph (Ill)

We have drawn the conclusion that in (II) and (III) the anions exist in various stereo- isomeric forms and that compounds (II) and (III) are stereoisomers. Compounds (I)-(III) do not have a mobile hydrogen atom and therefore they cannot display tautomerism analogous to the complex-salt tautomerism of 1,3,2,5-dioxaborataphosphorinanes~ The lack of tautomeric mobility in these compounds makes it possible to determine the spatial structure of the anions In solution (I) can exist as a mixture of conformers, but (II) and (III) as a mixture of stereoisomers. The presence of only two signals in the 31p NMR spectra of (II) and (III) points to the fact that in solutions each of them exists as one prevailing stereoisomer.

The PMR spectra make it possible to determine the conformations of the cyclic fragments and to determine the orientation of the substituents at the rings. For (I) and (III) the signals of the methylene and methine protons are symmetric doublets, which is evidence of their equivalency and consequently of the equatorial orientation of the phenyl groups in positions 4 and 6 of (III). This means that the six-membered cyclic anions of (I) and (III) have the chair conformation. The signal of the methine protons of (II) is an asymmetric quartet, characteristic of nonequivalent methine groups [7]. Therefore, the borate anion in (II) has a twisted conformation~ This is confirmed by the low value of the chemical shift of one of the signals in the Sip NMIR spectra of this compound.

With dihedral angles of 180 and 60 ~ between the planes in which lie the bonds X=P-C and P-C-H of the fragment X=P-C-H (X = O~ S, Se)~ the 2JpH spin-spi n coupling constants have the value 13-15 and 0-5 Hz, respectively [7]. The value of the spin-spin coupling con- stant of (I), being 4 Hz, is evidence that the equilibrium of the conformers is shifted to the side of the form with axial orientation of the phenyl at the phosphorus atom of the ring~ but for (III) the value of the spin-spin coupling constant is 12 Hz, which points to equatorial orientation of the phenyl at the phosphorus atom of the ring.

Compounds (I)-(III) are of interest for studying complex-salt tautomerism by means of Sip NMR spectroscopy because they are models of the cyclic salt form of the tautomeric equi- librium. Moreover, with a mobile hydrogen atom in the phosphonium cation of compounds simi- lar to (I)-(III) the occurrence of tautomerism with direct participation of the phosphorus atom in the formation of tautomeric forms is possible.

EXPERIMENTAL

PMR spectra were recorded with a Varian T-60 spectrometer (60 MBz) at 34o5~ with TMS as internal standard, alp NMR spectra were taken on a KGU-4 NMR spectrometer (10.2 MHz with proton noise decoupling at a frequency of 25.2 MHz). IR spectra were taken on a UR-20 spec- trometer.

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Methyltriphenylphosphonium 2~2~5-triphenyl-5-oxo-l,3~2,5-dioxaborataphosphorinane (I). To 1 g (2 mmoles) of dipropylammonium-2,2,5-triphenyl-5-oxy-l,3,2,5-dioxaborataphosphorinane [8] in 5 ml of acetonitrile was added 0.9 g (2 mmoles) of methyltriphenylphosphonium iodide. The mixture was heated until the compounds had dissolved and i0 ml of water was added. The solution was extracted with benzene (15 • 2 ml), the benzene was evaporated under vacuum, the residue was dissolved in EtOH, and extracted with ether (20 • 2 ml). The solvent was evaporated and the residue, 0.4 g (30%), was crystallized from MeCN, mp 129~ 31p NMR spec- trum (acetone, 6, ppm): 30.22. Found %: C 74.38, H 5,67, P 9.67. C~gH3vP203B. Calculated %: C 74.76, H 5.91, P 9.90~

Methyltriphenylphosphonium 2,2~4,5,6-pentaphenyl-5-oxo-l~3,2~5-dioxaborataphosphorinane (II). In a mixture of i0 ml of MeCN and 15 ml of benzene were dissolved 0.9 g (1.5 mmoles) of triethylammonium 2,2,4,5,6-pentaphenyl-5-oxo-l,3,2,5-dioxaborataphosphorinane [3] and 0.6 g (1.5 mmoles) of methyltriphenylphosphonium iodide. To this solution was added I0 ml of water, after 16 h the water layer was separated, the organic layer was extracted with i0 ml of water, and the solvent was evaporated under vacuum. The residue was dissolved in ace- tone, ether was added, the precipitate was filtered off, and washed with ether. Yield 0.3 g (26%) of (II), mp 172~ 31p NMR spectrum (DMF, 6, ppm): 44.22. Found %: C 78.45, H 5.76, P 7.54. CsIH~sP20~B. Calculated %: C 78.66, H 5.78, P 7.97.

Methyltriphenylphosphonium 2~2~4~5~6-pentaphenyl-5-oxo-l~3~2~5-dioxaborataphosphorinane (III). A mixture of 1.06 g (2 mmoles) of the sodium salt of methoxy(diphenyl)borataoxy- benzyl(hydroxybenzyl)phenylphosphine oxide and 0.82 g (2 mmoles) of methyltriphenyiphos- phonium iodide was dissolved in a benzene-acetonitrile mixture (5:1). To the solution was added i0 ml of water, the organic layer was separated and concentrated, and the residue was crystallized from acetone. Yield 0.91 g (55%) of (III), mp 169-170.5~ 31p NMR spectrum (DMF, 6, ppm): 23.21. Found %: C 78.39, H 5.43, P 7.67. C51H4sP20~B. Calculated %: C 78.66, H 5~ P 7.97.

CONCLUSIONS

Reaction of ammonium 2,2,5-triphenyl-4,6-disubstituted 1,3,2,5-dioxaborataphosphorinane oxides or the sodium salt of methoxy(diphenyl)borataoxybenzyl(hydroxybenzyl)phenylphosphine oxide with methyltriphenylphosphonium iodide yields methyltriphenylphosphonium 2,2,5-tri- phenyl-4,6-disubstituted 1,3,2,5-dioxaborataphosphorinane oxides.

LITERATURE CITED

B. A. Arbuzov, O. A. Erastov, and G. N. Nikonov, Izv. Akad. Nauk SSSR, Ser. Khim., 2089 (1984)o

Bo A. Arbuzov, G. N. Nikonov, and O. A. Erastov, Izv. Akad. Nauk SSSR, Sero Khim~ 2362 (1985)o Bo A. Arbuzov, G. N. Nikonov, and O. A. Erastov, !zv. Akado Nauk SSSR, Ser. Khim., 2369 (1985).

B. A. Arbuzov, G. N. Nikonov, and O. A. Erastov, Izv. Akad. Nauk SSSR, Ser, Khim., 171 (1986).

B. A. Arbuzov, G. N. Nikonov, A. A. Karasik, and O. A. Erastov, Izv. Akad. Nauk SSSR, Set. Khim., 1641 (1986). G. N. Nikonov, A. S. Balueva, A. A. Karasik, et al., Izv. Akad. Nauk SSSR, Ser. Khim0, 155 (1988)o Bo A. Arbuzov, O. A. Erastov, G. N. Nikonov, and A. S. Ionkin, Izv. Akad. Nauk SSSR, Ser Khim., 2501 (1984).

G. N. Nikonov, A. A. Karasik, and O. A. Erastov, Izv. Akad. Nauk SSSR, Ser. Khim., 187 (1988).

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