Mendeleev Communications Electronic Version, Issue 5, 2001 1 An alternative reaction of ortho-(N-benzylidene)aminophenol with chlorophosphites: formation of 2-(2'-alkoxy)-2-oxo-3-phenyl-5,6-benzo-1,4,2-oxazaphosphorinanes Mudaris N. Dimukhametov,* Eugenia V. Bajandina, Elena Yu. Davydova, Alexey B. Dobrynin, Aidar T. Gubaidullin, Igor A. Litvinov and Vladimir A. Alfonsov A. E. Arbuzov Institute of Organic and Physical Chemistry, Kazan Scientific Centre of the Russian Academy of Sciences, 420088 Kazan, Russian Federation.Fax: +7 8432 75 5322; e-mail: mudaris@iopc.kcn.ru 10.1070/MC2001v011n05ABEH001478 The reactions of o-(N-benzylidene)aminophenol with ethylene chlorophosphite and diethyl chlorophosphite in CHCl3 in the absence of an external acceptor of HCl result in the formation of diastereomeric 2-(2'-alkoxy)-2-oxo-3-phenyl-5,6-benzo-1,4,2-oxazaphosphorinanes different in the configurations of phosphorus atoms.The reactions of PIII halides with compounds which contain both a hydroxy group and an imino C=N unit have not been widely studied. Several papers describe the formation of polycyclic phosphoranes via the reaction of Cl.PIII derivatives with phenols containing an imino group in the presence of a base.1.3 We have observed an alternative reaction pathway in similar systems.Here we report the reactions of o-(N-benzylidene)- aminophenol 1 with ethylene chlorophosphite and diethyl chlorophosphite. These reactions¢Ó were carried out in the absence of an external HCl acceptor, and they resulted in the formation of two stereoisomers (diastereomers A and B) of 2-(2'-alkoxy)-2-oxo- 3-phenyl-5,6-benzo-1,4,2-oxazaphosphorinanes 4 and 5 differing only in the configuration at the phosphorus atom.The diastereomeric ratio A:B in both cases was approximately equal to 2:1. Diastereomers 4A and 4B (from the reaction of imine 1 with ethylene chlorophosphite) and diastereoisomer 5A (from the reaction of imine 1 with diethyl chlorophosphite) were isolated by column chromatography on silica gel as air-stable colourless crystals.The structures of 2-(2'-chloroethoxy)-2-oxo-3-phenyl- 5,6-benzo-1,4,2-oxazaphosphorinane diastereomers 4A and 4B were determined by X-ray¢Ô diffraction analysis (Figure 1). The structures of products 5A and 5B formed in the reaction of imine 1 with diethyl chlorophosphite were determined by comparing their 1H NMR and IR spectra with those of diastereomers 4A and 4B.¡× In the 1H NMR spectrum of diastereomer 4A, the proton of the PCH fragment appears at d 4.81 ppm, whereas the analogous proton of diastereomer 4B occurs at a lower field (d 4.94 ppm).In addition, the magnitude of the geminal coupling 2JHP in 4A is approximately twice lower than that for diastereomer 4B. The 1H NMR spectrum of a mixture of the two diastereomers of 2-(2'-ethoxy)-2-oxo-3-phenyl-5,6-benzo-1,4,2-oxazaphosphor- ¢Ó A typical experimental procedure was as follows: A solution of 1 (7.1 mmol) in CHCl3 (5 ml) was added dropwise to a solution of 2 (7.1 mmol) in CHCl3 (10 ml) in a dry argon atmosphere, with cooling (10 ¡ÆC) and stirring.After stirring for 10 min at this temperature, the reaction mixture was warmed slowly to room temperature and additionally stirred for 2 h; then, it was evaporated to dryness in a vacuum.The residue was purified by column chromatography (silica gel; toluene. acetonitrile, 4:1). OH N CHPh 1 + (RO)2PCl CHCl3 OP(OR)2 N CHPh 2 H Cl (RO)2 = OCH2CH2O, (EtO)2 N P(OR)2 O Ph H Cl 3 N P O Ph H O OR' 4A,B R' = CH2CH2Cl 5A,B R' = Et Scheme 1 ¢Ô X-ray diffraction analysis.Crystallographic data for 4A and 4B at 20 ¡ÆC: crystals of C15H15ClNO3P 4A are orthorhombic, space group P212121, a = 8.857(6) A, b = 10.532(2) A, c = 16.40(1) A, V = 1529.5(1) A3, Z = 4, M = 323.72, dcalc = 1.41 g cm.3, m(CuK¥á) = 3.327 cm.1, F(000) = 672; crystals of C15H15ClNO3P 4B are monoclinic, space group P21/c, a = 8.70(2) A, b = 16.698(6) A, c = 10.942(6) A, b = 102.10(5)¡Æ, V = 1554.8(4) A3, Z = 4, M = 323.72, dcalc = 1.38 g cm.3, m(CuK¥á) = 3.273 cm.1, F(000) = 672.Intensities of 1816 reflections for M10 and 2377 reflections for M11 were measured on an Enraf Nonius CAD-4 diffractometer at 20 ¡ÆC (l CuKa radiation, w/2q scan technique, 2qmax < 144¡Æ for M10 and 114¡Æ for M11), of which 1710 and 2068 were with I > 3s for M10 and M11, respectively.The structures were solved by direct methods and difference Fourier syntheses using the SIR program4 and the MolEN package.5 All nonhydrogen atoms were refined anisotropically; H atoms located in .F maps were refined isotropically. The absolute crystal structure and the absolute configuration of a molecule of 4A were determined by the Hamilton test ratio6 with a probability of 95%.The final agreement factors are R 0.034, Rw 0.044 based on 1643 reflections with F2 ©ø 3s for 4A and R 0.034, Rw 0.046 based on 1955 reflections with F2 ©ø 3s for 4B. Atomic coordinates, bond lengths, bond angles and thermal parameters have been deposited at the Cambridge Crystallographic Data Centre (CCDC).For details, see ¡®Notice to Authors¡�, Mendeleev Commun., Issue 1, 2001. Any request to the CCDC for data should quote the full literature citation and the reference number 1135/96. ¡× 1H and 31P NMR spectra (solvent: CD3CN) were measured on Bruker WM-250 (1H, 250 MHz, TMS) and Bruker MSL-400 (31P, 162 MHz, 85% H3PO4) instruments. IR spectra were recorded on a UR-20 spectrometer. Compound 4.Overall yield of diastereomers 4A + 4B is 73%. Diastereomer 4A: mp 149.150 ¡ÆC. 1H NMR, d: 3.51 (m, 2H, CH2Cl), 3.91 (m, 1H, OCH), 4.08 (m, 1H, OCH'), 4.81 (d, 1H, CHP, 2J 10.6 Hz), 6.80.7.04 (m, 4H, C6H4), 7.44.7.60 (m, 5H, Ph). 31P NMR, d: 10.6. IR (vaseline oil, KBr, n/cm.1): 1030, 1043 (P.O.C), 1222, 1252 (P=O), 3275 (N.H). Found (%): C, 55.74; H, 4.68; Cl, 10.48; N, 4.38; P, 9.31.Calc. for C15H15ClNO3P (%): C, 55.64; H, 4.64; Cl, 10.97; N, 4.33; P, 9.58. Diastereomer 4B: mp 90.91 ¡ÆC. 1H NMR, d: 3.76 (m, 2H, CH2Cl), 4.37 (m, 2H, OCH2), 4.94 (d, 1H, CHP, 2J 20.4 Hz), 6.76.7.05 (m, 4H, C6H4), 7.39 (m, 5H, Ph). 31P NMR, d: 11.2. IR (vaseline oil, KBr, n/cm.1): 1038, 1088 (P.O.C), 1230, 1250 (P=O), 3253 (N.H). Found (%): C, 55.85; H, 4.41; Cl, 11.21; N, 4.19; P, 9.12.Calc. for C15H15ClNO3P (%): C, 55.64; H, 4.64; Cl, 10.97; N, 4.33; P, 9.58. Compound 5. Overall yield of diastereomers 5A + 5B is 79%. Diastereomer 5A: mp 138.139 ¡ÆC. 1H NMR, d: 1.08 (t, 3H, Me, 3J 7.5 Hz), 3.83 (m, 1H, OCH), 3.97 (m, 1H, OCH'), 4.78 (d, 1H, CHP, 2J 11.4 Hz), 6.81.7.03 (m, 4H, C6H4); 7.39.7.62 (m, 5H, Ph). 31P NMR, d: 10.3.IR (vaseline oil, KBr, n/cm.1): 1035 (P.O.C), 1205, 1260 (P=O), 3292 (N.H). Found (%): C, 62.44; H, 5.60; N, 4.78; P, 10.68. Calc. for C15H16NO3P (%): C, 62.28; H, 5.54; N, 4.84; P, 10.78. Mixture of diastereomers 5A + 5B, 1:1.3. Light-brown oil, nD 20 1.5670. IR (KBr, n/cm.1): 1025, 1035, 1070 (P.O.C), 1210, 1223, 1260 (P=O), 3280, 3292 (N.H). Found (%): C, 62.02; H 5.16; N 4.19; P 9.12.Diastereomer 5B: 1H NMR, d: 1.26 (t, 3H, Me, 3J 7.1 Hz), 4.23 (m, 2H, OCH2), 4.87 (d, 1H, CHP, 2J 19.5 Hz), 6.75.7.07 (m, 4H, C6H4), 7.27.7.78 (m, 5H, Ph). 31P NMR, d: 12.0.Mendeleev Communications Electronic Version, Issue 5, 2001 2 inane 5 formed in the reaction of imine 1 with diethyl chlorophosphite shows two doublets at d 4.76 (J 11.4 Hz) and 4.87 ppm (J 19.5 Hz).The 1H NMR spectrum of the isolated product 5A exhibits a doublet at d 4.78 ppm (J 11.4 Hz). Based on this observation and the earlier result for diastereomers 4A and 4B, we can conclude that the isolated diastereomer of 5 has the structure of 5A, which is analogous to diastereomer 4A, i.e., the alkoxy group in both cases adopts an axial orientation. The IR spectra of diastereomers 4A, 4B, 5A and 5B are similar with the most characteristic absorption band for the secondary amino group NH at 3250–3280 cm–1.The formation of 1,4,2-oxazaphosphorinanes 4 and 5 in the course of the reaction of 1 with chlorophosites can be illustrated by Scheme 1. Initially formed iminium salts 2 undergo intramolecular cyclization by the nucleophilic attack of the PIII atom at the electrophilic carbon atom of the imonium group, resulting in the formation of quasiphosphonium salts 3.The latter give final products 4 and 5 according to the second stage of the Arbuzov reaction. References 1 A. Schmidpeter and J. H. Weinmaier, Angew. Chem., 1975, 87, 517. 2 A. Schmidpeter and J. H. Weinmaier, Chem. Ber., 1978, 111, 2086. 3 S. D. Harper and A.J. Arduengo, J. Am. Chem. Soc., 1982, 104, 2497. 4 A. Altomare, G. Cascarano, C. Giacovazzo and D. Viterbo, Acta Crystallogr., 1991, A47, 744. 5 L. Straver and A. J. Schierbeek, MolEN, Structure Determination System, Nonius B.V., 1994, vol. 1, p. 180. 6 W. C. Hamilton, Acta Crystallogr., 1965, 18, 502. C(17) C(18) C(16) C(15) C(13) N(4) C(3) C(5) C(6) C(7) C(8) C(9) C(10) C(14) O(1) P(2) O(2) O(3) C(11) C(12) Cl(2) Cl(2) C(12) C(11) O(3) P(2) O(1) O(2) C(17) C(16) C(15) C(14) C(13) N(4)C(3) C(5) C(6) C(7) C(8) C(9) C(10) C(18) Figure 1 Molecular structure of diastereomers A,B of compound 4.For 4A, selected bond lengths (Å) : P(2)–O(1) 1.569(2), P(2)–O(2) 1.466(2), P(2)–O(3) 1.572(2), P(2)–C(3) 1.815(2), N(4)–C(3) 1.450(3), N(4)–C(5) 1.394(3), O(1)–C(6) 1.407(3), C(5)–C(6) 1.402(3), C(3)–C(13) 1.511(3); selected bond angles (°): O(1)–P(2)–O(2) 113.0(1), O(1)–P(2)–O(3) 101.8(1), O(1)–P(2)–C(3) 103.0(1), O(2)–P(2)–O(3) 114.9(1), O(2)–P(2)–C(3) 115.5(1), O(3)–P(2)–C(3) 107.0(1), P(2)–O(1)–C(6) 124.5(2), P(2)–O(3)–C(11) 122.9(2), C(3)–N(4)–C(5) 117.6(2), P(2)–C(3)–N(4) 107.1(2), P(2)–C(3)–C(13) 110.4(2), N(4)–C(3)–C(13) 113.6(2), N(4)–C(5)–C(6) 121.1(2), O(1)–C(6)–C(5) 121.2(2), O(1)–C(6)–C(7) 116.8(2).For 4B, selected bond lengths (Å): P(2)–O(1) 1.584(1), P(2)–O(2) 1.459(2), P(2)–O(3) 1.559(1), P(2)–C(3) 1.810(2), N(4)– C(3) 1.457(2), N(4)–C(5) 1.386(2), O(1)–C(6) 1.413(2), C(5)–C(6) 1.390(2), C(3)–C(13) 1.509(2); selected bond angles (°): O(1)–P(2)–O(2) 113.39(8), O(1)–P(2)–O(3) 102.83(7), O(1)–P(2)–C(3) 102.76(8), O(2)–P(2)–O(3) 115.74(7), O(2)–P(2)–C(3) 116.68(8), O(3)–P(2)–C(3) 103.65(8), P(2)– O(1)–C(6) 120.5(1), P(2)–O(3)–C(11) 121.6(1), C(3)–N(4)–C(5) 122.2(1), P(2)–C(3)–N(4) 105.9(1), P(2)–C(3)–C(13) 111.8(1), N(4)–C(3)–C(13) 111.7(1), N(4)–C(5)–C(6) 122.7(1), O(1)–C(6)–C(5) 120.7(1), O(1)–C(6)– C(7) 116.9(2). 4A 4B Received: 22nd May 2001; Com. 01/1804