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Russian Journal of Coordination Chemistry, Vol. 26, No. 9, 2000, pp. 670­676. Translated from Koordinatsionnaya Khimiya, Vol. 26, No. 9, 2000, pp. 714­720. Original Russian Text Copyright © 2000 by Rybakov, Zhukov, Pasichnichenko, Babaev.

1,3-Di(2-oxopyridyl-1)acetone and Its Hydroperchlorate: Formation in the Hydrolysis of Annelated Munchnone and X-Ray Diffraction Study
V. B. Rybakov, S. G. Zhukov, K. Yu. Pasichnichenko, and E. V. Babaev
Moscow State University, Vorob'evy gory, Moscow, 119899 Russia
Received April 13, 2000

Abstract--1,3-Di(2-oxopyridyl-1)acetone is formed in the hydrolysis of mesoionic anhydro-3-[(1,2-dihydro2-oxopyridyl-1)acetyl]-2-hydroxyoxazolo[3,2-a]pyridinium hydroxide; attempts to perform cyclization of the obtained compound by acting with sulfuric and perchloric acids only yield the protonated product. The structures of some compounds are established by X-ray diffraction analysis.

Heterocyclic system I, containing coupled pyridine and oxazole fragments, has a mesoionic nature and is classified as a condensed munchnone [1]. The first members of this family were synthesized as early as in 1959 [2], and their chemical properties were investigated in detail in [3]. Unsubstituted munchnone I,
O N+ ( II ) O O+ N (I) O+ N ( III ) O

formed in the deprotonation of salts II, is unstable and readily dimerizes to give compound III. Introduction of the acyl group remarkably stabilizes the mesoionic system; therefore, the acyl derivatives with general formula IV (to which, in particular, dimer III should be referred) are quite stable.
O+ N (IV ) O O­ R

Et3N

O

­

RCOX

O­

N

O

Our interest in the chemistry of this class of mesoionic heterocycles is due to their structural properties and the possibility of using them in heterocyclic synthesis. Earlier [4], on the basis of the X-ray powder difO+ N (IV ) O O R
­

fraction data, we proved the unusual ilide structure of the molecule IV (R = Ph). In addition, we discovered a new type of recyclization of mesoionic compounds IV resulting in the formation of oxazolopyridinium salts VI [5]:
O O+ N (VI ) R

H2O

N (V ) O R

H+ ­ H2O

Such a recyclization proceeds via the stage of formation of pyridones V, which can be separated as inter-

mediates; this transformation can be run without their separation (a one-pot process).

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Dimer III can be formally classified as the acyl derivative IV, and, therefore, one can expect that mesoionic system III will undergo recyclization to produce cationic heterocycle VII. In this paper, the data obtained in our attempt to carry out the hydrolytic cleavage and recyclization of mesoionic compound III are reported.

We found that the hydrolytsis of molecule III gives 1.3-di(2-oxopyridyl-1)acetone (VIII) with a high yield. Compound VIII was described and previously synthesized by another method [6]. The constants of the compound, which we obtained, agree with the literature data. The structure of the compound was confirmed by X-ray diffraction analysis.
­ O+ ClO4

N O+ N O ( III ) O­ (VII )
H2O

O N

N N O (VIII)

O O N

H2SO HClO

4 4

O N (IX ) O+ ­ H ClO4 O O N

A common procedure used for cyclization of pyridones V into cations VI consists in their subsequent treatment with sulfuric and perchloric acids. In attempts to convert pyridone VIII into salt VII through such a cyclocondensation under similar conditions, we obtained an ionic compound, whose structure, however, did not correspond to that of the expected perchlorate VII (the expected downfield singlet of oxazole fragment was lacking in the 1H NMR spectrum of the obtained compound). The 1H NMR spectrum of compound VII resembles that of starting compound VIII. According to X-ray diffraction data, the obtained compound has structure IX. A systematic search for the above-mentioned structures and their analogs in the Cambridge Crystallographic Database (version 5.18 1999) [7] was unsuccessful, which triggered their study by X-ray diffraction analysis. EXPERIMENTAL Synthesis and spectral data. Compound III (C14H10N2O4) was obtained from perchlorate I using the procedure reported in [3]. The yield was 65%. 1H NMR spectrum (DMSO-d ; , ppm): 7.74, 6 d (OC­C­CH­C); 8.06, dd (N­C­C­CH­C­CO); 7.43, dd (N­C­CH­C); 6.21, d (N­CH­C); 5.15, s (CO­CH2); 7.59, m (N­CH­C + N­CO­C­CH); 6.39, d (N­CO­CH­C); 6.21, dd (N­C­CH­C). The 1H NMR spectrum of compound III in trifluoroacetic acid was described in [3]. Synthesis of compound VIII. Compound III (1.58 g, 5.9 mmol) was boiled in 10 ml of H2O for several hours
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until it completely dissolved. After the transparent solution was cooled, compound VIII precipitated and was filtered off, washed with 5 ml of ice-cooled water, and dried. The yield of compound VIII (C13H12N2O3) was 1.2 g (83%); Tm = 222°C (223°C [6]). The 1H NMR spectrum (DMSO-d6; , ppm): 7.55, dd (N­CH­C); 6.24, m (NC­CH­C); 7.42, m (OC­C­ CH); 6.40, d (OC­CH­C); 4.93, s (CO­CH2­N) or 7.55, dd (6-CH + 15-CH); 6.24, m (5-CH + 14-CH); 7.42, m (4-CH + 13-CH); 6.40, d (3-CH + 12-CH); 4.93, s (7-CH + 9-CH). IR spectrum (, cm­1): 1665 (NC=O), 1747 (CC=O). Synthesis of compound IX. Compound VIII (0.417 g, 1.7 mmol) was dissolved with stirring in concentrated H2SO4 (4.3 g) and allowed to stand overnight. The obtained solution was filtered off through a glass porous plate; the filtrate was diluted with 100 ml of cold water, and 1.5 ml of 70% HClO4 were added to it. The precipitated white needle crystals of compound IX were filtered off, washed with ice-cold water (2 â 5 ml), + and dried. The yield of compound IX (C13H13N2 O 3 · Cl O 4 ) was 0.416 g (51%); Tm = 278°C. The 1H NMR spectrum (DMSO-d6, , ppm): 7.55, dd (N­CH­C); 6.24, m (NC­CH­C); 7.44, m (OC­C­ CH); 6.40, d (OC­CH­C); 4.93, s (CO­CH2­H) or 7.55, dd (6-CH + 15-CH); 6.24, m (5-CH + 14-CH); 7.44, m (4-CH + 13-CH); 6.40, d (3-CH + 12-CH); 4.93, s (7-CH + 9-CH).
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Table 1. Crystallographic data and summary of data collection for compounds VIII and IX Parameter Empirical formula Crystal system a, å b, å c, å , deg Space group Z V, å3 Formula weight (calcd), g/cm3 , mm­1 min/max, deg Experimental range VIII C13H12N2O3 Monoclinic 9.167(4) 12.924(3) 10.372(3) 102.38(3) P21/a 4 1200.2(7) 244.25 1.352 0.098 2.55/25.97 ­ 11 h 11 ­6 k 15 ­5 l 12 512 2578 2304 212 0.973 0.0708 0.1479 0.1885 0.2057 0.289 ­ 0.213 IX C13H13N2 O 3 · Cl O Monoclinic 11.3328(19) 12.4738(12) 10.6234(18) 94.65(1) P21/c 4 1496.8(4) 343.70 1.525 0.294 1.80/26.97 ­ 14 h 14 0 k 15 0 l 13 708 3416 3238 257 1.055 0.0500 0.1035 0.0960 0.1213 0.359 ­ 0.259
+ ­ 4

F000 Total number of reflections Number of reflections with I > 2(I) Number of refined parameters GOF (F2) R1 (I > 2(I)) wR2(I > 2(I)) R1 (all data) wR2 (all data) max, e /A3 min, e /A3

IR spectrum (, cm­1): 1662 (NC=O), 1760 (CC=O). The 1H NMR spectra were recorded on a Bruker AM-400 instrument; and IR spectra, on a UR-20 spectrophotometer (suspension in mineral oil; samples of IX as pallets with CaF2). X-ray diffraction analysis of compounds VIII and IX was carried out using a CAD-4 automated diffractometer [8] (MoK radiation, graphite monochromator, scan mode). The unit cell parameters and crystal systems of VIII and IX were determined and refined from 24 reflections over the angle interval of 12°­13°. Diffraction data were preliminarily processed using the WinGX-98 program package [9]. The coordinates of non-hydrogen atoms in both compounds were determined by the direct method and

refined by the full-matrix least-squares method (SHELX97 [10]) in anisotropic approximation. Hydrogen atoms were located from difference synthesis and refined by the least-squares method in isotropic approximation. An attempt to locate the proton in compound IX was a failure. The crystallographic data and the details of data collection for compounds VIII and IX are summarized in Table 1; coordinates of atoms and their thermal parameters Uequiv/Uiso are given in Table 2; and bond lengths and angles, in Table 3 (C­H distances and HCH bond angles are not indicated). The selected torsion angles in the molecules are listed in Table 4. The geometry of the atoms in the molecules and their numbering are shown in Figs. 1 and 2. The schematic representation of molecules was obtained using the ORTEP-3 program [11].
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Table 2. Coordinates of atoms (â 104) and their equivalent isotropic thermal parameters Ueq /Uiso (â 103) for structures VIII and IX Atom N(1) C(2) O(2) C(3) C(4) C(5) C(6) C(7) C(8) O(8) C(9) N(10) C(11) O(11) C(12) C(13) C(14) C(15) H(3) H(4) H(5) H(6) H(7A) H(7B) H(9A) H(9B) H(12) H(13) H(14) H(15) Cl(1) O(1a) O(1b) O(1c) O(1d) x ­ 878(1) ­ 2349(2) ­ 3163(1) ­ 2733(2) ­ 1802(2) ­ 387(2) 42(2) ­ 353(2) ­ 431(2) ­ 989(1) 265(2) 6(1) ­ 1399(2) ­ 2326(1) ­ 1533(2) ­ 338(3) 984(3) 1140(2) ­ 3760(15) ­ 2145(15) 316(19) 848(18) 634(16) ­ 982(16) ­ 197(18) 1200(20) ­ 2348(13) ­ 300(20) 2060(20) 1990(30) y VIII 9393(1) 9539(1) 8782(1) 10 595(1) 11 370(1) 11 177(1) 10 200(1) 8346(1) 8006(1) 8505(1) 6949(1) 6562(1) 6186(1) 6207(1) 5817(2) 5907(2) 6292(2) 6610(2) 10 756(10) 12 051(10) 11 683(13) 10 020(12) 8304(11) 7899(11) 6422(12) 7035(14) 5591(8) 5700(15) 6392(15) 6870(18) 1389(1) 677(2) 367(1) 392(2) 832(2) 1597(2) 1856(2) 1689(2) 3045(2) 3781(1) 3404(2) 4626(1) 4588(2) 3563(2) 5980(2) 6972(2) 6855(2) 5702(2) ­ 146(12) 641(12) 2027(15) 2309(15) 1607(13) 1101(12) 2610(14) 3447(15) 5294(10) 7901(18) 7683(18) 5520(20) 51(1) 54(1) 84(1) 63(1) 70(1) 76(1) 65(1) 55(1) 48(1) 62(1) 61(1) 46(1) 65(1) 99(1) 93(1) 91(1) 106(1) 81(1) 49(4) 53(4) 91(6) 76(5) 59(4) 56(4) 77(5) 90(6) 18(3) 117(7) 128(7) 146(8) 7377(1) 6347(1) 5950(1) 5795(1) 6287(1) 7347(1) 7868(1) 7913(1) 7483(1) 6930(1) 7821(1) 7583(1) 6506(1) 5755(1) 6337(1) 7179(1) 8243(1) 8427(1) 5102(10) 5963(13) 7704(13) 8498(12) 7780(9) 8734(10) 7352(11) 8656(10) 5663(11) 7047(11) 8838(11) 9110(9) 595(1) 119(1) 1845(1) 112(1) 283(1) 9940(1) 10 377(1) 10 033(1) 11 140(1) 11 419(1) 10 977(1) 10 242(1) 9082(1) 7996(1) 7890(1) 7072(1) 6049(1) 5577(1) 6064(1) 4598(1) 4178(1) 4711(1) 5628(1) 11 414(9) 11 839(12) 11 161(11) 9921(10) 9201(9) 9107(10) 7114(9) 7133(9) 4312(10) 3573(11) 4482(11) 6023(8) 7875(1) 6958(1) 7893(1) 8822(1) 7845(1) z Ueq /Uiso , å2 x y IX ­ 529(1) ­ 1018(1) ­ 2115(1) ­ 304(1) 849(1) 1317(1) 631(1) ­ 1217(1) ­ 811(1) 100(1) ­ 1603(1) ­ 1019(1) ­ 1258(1) ­ 2012(1) ­ 654(1) 176(1) 427(1) ­ 170(1) ­ 614(10) 1278(14) 2010(13) 872(12) ­ 2084(10) ­ 982(11) ­ 2455(11) ­ 1723(10) ­ 814(11) 567(12) 944(12) ­ 61(10) 1433(1) 2007(1) 1672(1) 1949(1) 111(1) 43(1) 42(1) 58(1) 55(1) 69(1) 73(1) 61(1) 49(1) 40(1) 56(1) 46(1) 39(1) 46(1) 65(1) 61(1) 66(1) 64(1) 52(1) 59(3) 98(5) 91(5) 80(4) 53(3) 60(3) 66(4) 60(3) 69(4) 77(4) 78(4) 51(3) 43(1) 61(1) 74(1) 82(1) 81(1) z Ueq /Uiso , å2

For convenience, the geometrical fragments of molecules have a common numbering of atoms. RESULTS AND DISCUSSION An analysis of the geometry and structures of related compounds VIII and IX allows one to draw an indirect conclusion that the proton in cation IX is most
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likely bound to the amide oxygens O(2) and O(11) rather than to the ketone oxygen O(8) because the C(8)­O(8) distance in both structures is virtually the same (1.195(2) å in molecule VIII and 1.203(1) å in cation IX), whereas the C(2)­O(2) and C(11)­O(11) distances markedly increase when changing over from VIII to IX: from 1.231(2) to 1.288(1) å and from 1.211(2) to 1.275(1) å, respectively. This change in the
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Table 3. Bond lengths and angles in structures VIII and IX d, å Bond VIII Cl(1)­O(1b) Cl(1)­O(1d) Cl(1)­O(1a) Cl(1)­O(1c) N(1)­C(2) N(1)­C(6) N(1)­C(7) C(2)­O(2) C(2)­C(3) C(3)­C(4) C(4)­C(5) C(5)­C(6) C(7)­C(8) C(8)­O(8) C(8)­C(9) C(9)­N(10) N(10)­C(11) N(10)­C(15) C(11)­O(11) C(11)­C(12) C(12)­C(13) C(13)­C(14) C(14)­C(15) Angle VIII O(1b)Cl(1)O(1d) O(1b)Cl(1)O(1a) O(1d)Cl(1)O(1a) 1.405(2) 1.363(2) 1.447(2) 1.231(2) 1.425(2) 1.332(2) 1.391(2) 1.332(2) 1.490(2) 1.195(2) 1.520(2) 1.429(2) 1.369(2) 1.353(2) 1.211(2) 1.551(3) 1.337(3) 1.339(4) 1.302(3) , deg IX 110.04(6) 110.10(5) 109.23(6) IX 1.4184(9) 1.4205(9) 1.4234(9) 1.4295(9) 1.354(1) 1.364(2) 1.455(2) 1.288(1) 1.397(2) 1.350(2) 1.378(2) 1.338(2) 1.514(2) 1.203(1) 1.495(2) 1.454(1) 1.360(1) 1.366(1) 1.275(1) 1.400(2) 1.350(2) 1.385(2) 1.332(2) O(1b)Cl(1)O(1c) O(1d)Cl(1)O(1c) O(1a)Cl(1)O(1c) C(2)N(1)C(6) C(2)N(1)C(7) C(6)N(1)C(7) O(2)C(2)N(1) O(2)C(2)C(3) N(1)C(2)C(3) C(4)C(3)C(2) C(3)C(4)C(5) C(6)C(5)C(4) C(5)C(6)N(1) N(1)C(7)C(8) O(8)C(8)C(9) O(8)C(8)C(7) C(9)C(8)C(7) N(10)C(9)C(8) C(11)N(10)C(15) C(11)N(10)C(9) C(15)N(10)C(9) O(11)C(11)N(10) O(11)C(11)C(12) N(10)C(11)C(12) C(13)C(12)C(11) C(12)C(13)C(14) C(15)C(14)C(13) C(14)C(15)N(10) 122.3(1) 118.5(1) 119.2(1) 119.3(1) 126.8(2) 113.9(1) 122.5(2) 120.8(2) 119.0(2) 121.3(2) 113.4(1) 122.9(2) 123.9(1) 113.2(1) 113.0(1) 126.3(2) 115.6(1) 118.1(2) 119.8(2) 130.1(2) 110.2(1) 118.2(2) 124.9(2) 118.7(2) 121.8(2) Angle VIII , deg IX 109.05(6) 109.17(6) 109.22(6) 120.8(1) 119.0(1) 120.0(1) 116.1(1) 125.4(1) 118.4(1) 119.9(1) 120.5(1) 119.3(1) 121.0(1) 111.0(1) 122.9(1) 121.9(1) 115.3(1) 111.8(1) 121.7(1) 119.7(1) 118.4(1) 116.9(1) 126.5(1) 116.5(1) 121.5(1) 119.9(1) 119.2(1) 121.1(1)

Table 4. Selected torsion angles in structures VIII and IX Angle C(7)­N(1)­C(2)­O(2) C(2)­N(1)­C(7)­C(8) N(1)­C(7)­C(8)­O(8) O(8)­C(8)­C(9)­N(10) C(8)­C(9)­N(10)­C(11) C(9)­N(10)­C(11)­O(11) , deg VIII 2.1(3) ­ 97.8(2) 6.3(2) 7.8(2) 75.9(2) ­ 0.4(3) IX ­ 4.0(1) ­ 90.6(1) ­ 11.0(1) ­ 9.8(1) 89.2(1) 0.9(2)

NC­O bond lengths corresponds to the decrease in their multiplicity upon protonaton of the O atom and agrees with the general trend in the changing of the length for other bonds in the pyridine rings when going over from the neutral molecule to the cation. The pyridone fragments of the nonprotonated molecule VIII are characterized by alternating ordinary and double bonds. Obviously, cation IX with protonated amide oxygen atom can be represented not only by the resonance structure with alternating bond lengths (A) but also by the structure with equalized bond lengths in the six-membered ring (B). Such a change (elongation
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O(11) C(12) O(2) C(3) C(2) N(1) C(8) C(7) C(5) C(6) C(9) C(15) C(14) O(8) N(10) C(11) C(13)

C(4)

Fig. 1. Structure, numeration, and thermal vibrations of atoms (50%) in compound VIII.

O(1d)

O(1c) C(11)

O(1a)

O(1b)

O(11) C(3) O(2) C(12)

C(2) C(4) N(1) C(5)

O(8)

C(11) N(10)

C(13) C(8) C(6) C(7) C(9) C(14) C(15)

Fig. 2. Structure, numeration, and thermal vibrations of atoms (50%) in compound IX. RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 26 No. 9 2000


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of double bonds and shortening of ordinary bonds) is really observed in going over from molecule VIII to cation IX:
H+

the anion slightly turns the heterocycle planes, thus increasing the dihedral angles between them: from 66.75(8)° in molecule VIII to 79.35(4)° in cation IX. ACNOWLEDGMENTS This work was supported by the Russian Foundation for Basic Research, project nos. 99-03-33076 and 99-07-90133 (for purchasing the license to use the Cambridge Crystallographic Database). REFERENCES
1. Newton, C.G. and Ramsden, C.A., Tetrahedron, 1982, vol. 38, p. 2965. 2. Lawson, A. and Miles, D.H., J. Chem. Soc., 1959, p. 2865. 3. Boyd, G.V. and Wright, P.H., J. Chem. Soc., Sect. C., 1970, p. 1486. 4. Zhukov, S.G., Babaev, E.V., Chernyshev, V.V., et al., Z. Kristallogr., 2000, vol. 215, p. 306. 5. Babaev, E.V. and Orlova, I.A., Khim. Geterotsikl. Soedin., 1997, no. 4, p. 569. 6. Winterfeld, K. and Michael, H., Chem. Ber., 1960, vol. 93, p. 61. 7. Allen, F.H. and Kennard, O., Chem. Des. Autom. News, 1993, vol. 8, p. 31. 8. Enraf-Nonius CAD-4 Software. Version 5.0 Enraf-Nonius, Delft, the Netherlands, 1989. 9. Farrugia, L.J., WinGX-98. X-Ray Crystallographic Programs for Windows, Univ. of Glasgow, UK, 1998. 10. Sheldrick, G.M., SHELX97. Program for the Solution and Refinement of Crystal Structures, Univ. of GÆttingen, Germany, 1997. 11. Bernett, M.N. and Jahnson, C.K., ORTEP-3. Report ORNL-6895, Oak Ridge National Laboratory, 1996.

N

O

N

OH+

N+

OH

(A )

(B )

This pattern of protonation could be experimentally confirmed through the objective location of the proton of one of the amide oxygen atoms. However, it was experimentally established that the proton is delocalized between two positions (O(2) and O(11) atoms), and it was difficult to determine its location because of a small scattering factor. Accurate determination of the proton position could be performed by using the method of neutron diffraction on deuterium nuclei. One more indirect piece of evidence supporting the protonation of the amide oxygen atoms O(2) and O(11) in structure IX is the decrease of the O(2)C(2)N(1) bond angle from 119.3(1)° to 116.1(1)° and the decrease of the O(11)C(11)N(10) bond angle from 119.8(2)° to 116.9(1)°, with the O(8)C(8)C(7) and O(8)C(8)C(9) bond angles remaining virtually unchanged. The principal difference between the conformation of the O(2)­C(2)­N(1)­C(7)­C(8)­O(8) and O(11)­ C(11)­N(10)­C(9)­C(8)­O(8) structural fragments in compounds VIII and IX cannot be established from the torsion angles (Table 4) because a slight difference can ­ be due to the effect of a balky tetrahedral Cl O 4 anion which "penetrates" into the space between oxygens O(2)···O(8)···O(11) in the organic cation. In this case,

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