Maghsoodlou M. T , Heydari R , Hazeri N , Habibi-Khorassani S. M , Nassiri M , Kazemian M. A , Salehzadeh J , Hajizadeh M, Ghasemzadeh M , Mosaddegh E. Synthesis of Heterocyclic Stable Phosphorus Ylides from Reaction Between Triphenylphosphine and Activated Acetylenic Esters in the Presence of Biological Active NH Heterocyclic Compounds. Biomed Pharmacol J 2008;1(1).

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Malek Taher Maghsoodlou^*, Reza Heydari, Norollah Hazeri, Sayyed Mostafa Habibi-Khorassani, Mahmoud Nassiri, Mohammad Amin Kazemian, Jaber Salehzadeh, Mahbobeh Hajizadeh, Marjan Ghasemzadeh and Elaheh Mosaddegh

Department of Chemistry, The University of Sistan and Balouchestan.

Abstract

Triphenylphosphine reacts with dialkyl acetylenedicarboxylates in the presence of biological active NH heterocyclic compounds, such as (2H) -3-pyridazinone, 1-phenyl-3-pyrazolid- inone, 2,4-thiazolinedione, Rhodanine, 4,5,6,7-tetrahydroindazole and 3-methyl- pyrazole to generate stable phosphorus ylides. These compounds exist in solution as a mixture of two geometrical isomers as a result of restricted rotation around the carbon-carbon partical double bond resulting from conjugation of the ylide moiety with the adjacent carbonyl group.

Keywords

Activated acetylenic esters; NH heterocyclic compounds; Triphenyl- phosphine

Introduction

Phosphorus-carbon bond formation^[1-15] is an active and important research area, as new reactions are continuously being developed for the preparation of organophosphorus compounds such as phosphinates and phosphonates.^[16-24] Over the last few years, the quest for the synthetic efficiency has gained remarkable importance, partly due to the need reduce waste.²⁵ Given the increasing industrial, biological and synthetic impact of organophosphorus compounds.^[26-30] The successful attack by nucleophilic trivalent phosphorus on a carbon atom is facilitated when the latter is part of, or conjugated with, a carbonyl group, or when it is part of an unsaturated bond otherwise activated.^[27-29] There are many studies on the reaction between trivalent phosphorus nucleophiles and α, β–unsaturated carbonyl compounds in the presence of a proton source such as alcohol or phenol.^[31,32] Here we wish to report a simple one-pot synthesis of heterocyclic compounds-containing stable phosphorus ylides. Previously, the pyrazole and thiazole moieties and their derivatives have been used commercially as pharmaceuticals, pesticides and dyestuffs.^[33] Thus, the reaction of triphenylphosphine 1 with dialkyl acetylenedicarboxylates 2 in the presence of NH heterocyclic compounds 3 such as 3-methylpyrazole and etc were undertaken to generate the corresponding stable heterocyclic phosphorus ylides 4 in excellent yields (see Scheme 1).

Scheme 1   Click here to View scheme

Result and discussion

In the current work, stable phosphorus ylides from reaction between triphenylphosphine 1 and dialkyl acetylenedicarboxylates 2 in the presence of N-H acids 3, such as (2H)-3-pyridazinone, 1-phenyl-3-pyrazolidinone, 2,4-thiazolinedi- one, Rhodanine,  4,5,6,7-tetrahydroindazole and 3-methylpyrazole  led to 4 in excellent yields (see Scheme 1). The reactions (4a-m) were carried out in ethyl acetate solvent at room temperature and were finished within a few minutes. The ¹H and ¹³C NMR spectrum of the crude product clearly indicated the formation of compounds 4a-m. Any products other than 4a-m could not be detected by NMR spectroscopy. The structures of compounds 4a-m were deduced from their IR, ¹H, ¹³C, ³¹P NMR spectra, Mass spectrometry and elemental analysis. The mass spectra of compounds 4a-m displayed molecular ion peaks at appropriate values, which were consistent with 1:1:1 adducts of NH heterocyclic compounds, dialkyl acetylenedicarboxylates and triphenylphosphine. Although the presence of the ³¹P nucleus complicates both the ¹H and ¹³C NMR spectra of 4a, it helps in assignment of the signals by long-range couplings with the ¹H and ¹³C nuclei (see Experimental section). The ¹H, ¹³C, and ³¹P NMR spectra of ylides 4a-m are consistent with the presence of two isomers. The ylides moieties of these compounds are strongly conjugated with the adjacent carbonyl group and rotation around the partial double bond in (E)-4 and (Z)-4 geometrical isomers is slow on the NMR timescale at ambient temperature (see Scheme 2). As can be seen, only one geometrical isomer was observed for di-tert-butyl derivatives of 4, presumeably, because of the bulky tert-butyl groups. (see Scheme 2).

Scheme 2   Click here to View scheme

On the basis of the well established chemistry of trivalent phosphorus nucleophiles, ^[3-7] it is reasonable to assume that phosphorus ylide 4 results from the initial addition of triphenylphosphine to the acetylenic esters and subsequent protonation of the 1:1 adduct by the NH heterocyclic compounds to form phosphoranes 4 (see Scheme 3).

Scheme 3   Click here to View scheme

The ¹H NMR 500 MHz spectra of 4a showed four sharp lines at δ = 3.14, 3.72, 3.61 and 3.66 ppm arising from methoxy protons. Methine protons appeared as two doublet peaks at δ= 5.64 ppm (1H, d, ³J_PH=17.0 Hz, P-C-CH) and 5.75 ppm (1H, d, ³J_PH=18.9 Hz, P-C-CH) respectively for the E and Z geometrical isomers. The aromatic protons appeared as a multiplet at δ = 6.65–7.90 ppm (18H, m, 3C₆H₅ and C₄H₄N₂O). The ¹³C NMR spectrum of 4a displayed 28 distinct resonances in a good agreement with the mixture of two conformational isomers. The ¹H and ¹³C NMR spectra of compounds 4b-m are similar to those of 4a, except for signals from the ester group which appear as characteristic resonance lines with the corresponding chemical shifts. The structural assignments of 4a-m were made on the basis of the ¹H and ¹³C NMR spectra that were supported by their IR spectra. The carbonyl region of the spectra exhibited two distinct absorption bands for each compound related to ester groups of yilde moiety (see Experimental section).

Briefly, we have prepared novel phosphorus ylides using a one-pot reaction between triphenylphosphine and dialkyl acetylenedicarboxylates in the presence of strong NH heterocyclic compounds. The present method carries the advantage that, not only is the reaction performed under neutral conditions, but also the substances can be mixed without any activation or modifications. Heterocyclic compounds-containing stable phosphorus ylides 4a-m may be considered as potentially useful synthetic intermediates. It seems that, the procedure described here may be employed as an acceptable method for the preparation of phosphoranes with variable functionalities.

Experimental 

Melting points and IR spectra of all compounds  were measured on an Electrothermal 9100 apparatus and a Shimadzu IR-460 spectrometer respectively.  Also, the ¹H, ¹³C, and ³¹P NMR spectra were obtained from a BRUKER DRX-500 AVANCE instrument with CDCl₃ as an solvent at 500.1, 125.8, and 202.4 MHz respectively. Elemental analyses for C, H, N were performed using a Heraeus CHN-O-Rapid analyzer. In addition, the mass spectra were recorded on a GCMS-QP 5050A mass spectrometer operating at an ionization potential of 70 eV. (2H)-3-pyridazinone, 1-phenyl-3-pyrazolidinone, 2,4-thiazolinedione, Rhodanine,  4,5,6,7-tetrahydroindazole, 3-methylpyrazole  dialkyl acetylenedicarboxylates and triphenlphosphine, were purchsed from Fluka, (Buchs, Switzerland) and used without further purifications.

General Procedures (Exemplified by 4a)

Preparation of dimethyl 2-( 3-pyridazinone-2-yl)-3-(triphenylphosphanylidene) butanedioate (4a).

To a magnetically stirred solution of triphenylphosphine (0.26 g or 1 mmol) and (2H)-3-pyridazinone (0.96 g or 1 mmol) in 10 mL of dry ethyl acetate was added, dropwise, a mixture of dimethyl acetylenedicarboxylate (0.14g or 1 mmol) in 5 mL of dry ethyl acetate over 10 min. After a few minutes stirring at room temperature, the product was filtered and washed with cold diethyl ether (3 × 5 mL).

White powder, m.p 93-95°C, 0.46 g, yield 90%, IR (v_max, cm^-1): 1733 and 1664 (C=O). 500 (M⁺,7), 438 (M-2OMe, 37), 382 (M-2CO₂Me 46), 262 (PPh₃, 80), 183 (PPh₂, 48), 108 (PPh, 43), 77 (Ph, 35). Anal. calcd. for C₂₈H₂₅N₂O₅P (500): C, 67.17; H, 5.04; N, 5.60 %. Found: C, 67.21; H, 4.95; N, 5.67 %.

Major isomer Z-4a (60%): ¹H NMR (500.1 MHz, CDCl₃): δ 3.14 and 3.72 (6H, 2s, 2OCH₃), 5.64 (1H, d, ³J_PH = 17.0 Hz, P=C-CH), 6.65-7.90 (18Haro, m, 3C₆H₅ and C₄H₃N₂O). ¹³C NMR (125.8 MHz, CDCl₃): δ 42.75 (d, ¹J_PC = 126.8 Hz, P=C), 49.34 and 52.30 (2s, 2OCH₃), 63.72 (d, ²J_PC=16.0 Hz, P-C-CH), 108.89 (1C, C₄H₃N₂O), 126.37 (d, ¹J_PC = 92.0 Hz, C_ipso), 127.84 (d, ³J_PC = 11.9 Hz, C_meta), 132.19 (d, ⁴J_PC = 2.1 Hz,  C_para), 133.57 (1C, C₄H₃N₂O), 133.28 (d, ²J_PC = 9.0 Hz, C_ortho), 147.55 and 162.13 (2C, C₄H₃N₂O), 165.42 (d, ³J_PC = 15.7Hz, C=O), 171.57 (d, ²J_PC = 13.5 Hz, P-C=C). ³¹P NMR (202.4 MHz, CDCl₃): δ 23.12 (Ph₃P⁺-C).

Minor isomer E-4a (40%): ¹H NMR (500.1 MHz, CDCl₃): δ 3.61 and 3.66 (6H, 2s, 2OCH₃), 5.75 (1H, d, ³J_PH = 18.9 Hz, P=C-CH), 6.65-7.90 (18Haro, m, 3C₆H₅ and C₄H₃N₂O). ¹³C NMR (125.8 MHz, CDCl₃): δ 42.86 (d, ¹J_PC = 136.0 Hz, P=C), 50.32 and 52.32 (2s, 2OCH₃), 63.57 (d, ²J_PC = 15.8 Hz, P-C-CH), 108.93 (1C, C₄H₃N₂O), 125.67 (d, ¹J_PC = 92.1 Hz, C_ipso), 128.27 (d, ³J_PC = 12.0 Hz, C_meta), 132.23 (d, ⁴J_PC = 2.2 Hz, C_para), 134.13 (1C, C₄H₃N₂O), 133.59 (d, ²J_PC = 9.8 Hz, C_ortho), 147.63 and 163.14 (2C, C₄H₃N₂O), 165.72 (d, ³J_PC =14.8 Hz, C=O), 169.83 (d, ²J_PC = 12.5 Hz, P-C=C). ³¹P NMR (202.4 MHz, CDCl₃): δ 22.97 (Ph₃P⁺-C ).

dimethyl-2-(1-phenyl-3-pyrazolidinone-2-yl)-3-(triphenylphosphanylidene) butanedioate (4b).

white powder, m.p 166-168°C, 0.53g, yield 93%, IR (υ_max, cm^-1) 1753 and 1676 (C=O). MS  (m/z, %): 446 (M-2CO₂Me, 17), 304 (M-PPh and Ph, 38), 262 (PPh₃, 76), 183 (PPh₂, 36), 108 (PPh, 43), 77 (Ph, 14). Anal. calcd. for C₃₃H₃₁N₂O₅P (566): C, 70.12; H,5.56; N, 5.02%. Found: C, 69.96; H, 5.48; N, 4.95%.

Major isomer Z-4b (68%):  ¹H NMR (500.1 MHz, CDCl₃): δ  2.43(2H, m, H₂C-CO), 3.20(3H, s, OCH₃), 3.55(2H, m, H₂C-N), 3.81 (3H, s, OCH₃), 4.97 (1H_bro, P-C-CH), 6.99–7.71 (20H_arom, m, 4C₆H₅).  ¹³C NMR  (125.8 MHz, CDCl₃): δ 29.65 and 30.03 (2C, C₉H₉N₂O), 38.18 (d, ¹J_PC = 128.8 Hz, P=C), 49.68 and 52.08 (2s, 2OCH₃), 59.79 (d, ²J_PC = 16.2 Hz, P-C-CH), 116.56, 119.76, 123.03, 126.17 and 126.91 (5C, C₉H₉N₂O), 126.54 (d, ¹J_PC = 92.9 Hz, C_ipso), 128.50 (d, ³J_PC = 12.3 Hz, C_meta), 131.85 (C_para­), 132.07 (1C, C₉H₉N₂O), 133.73 (d, ²J_PC = 9.8 Hz, C_ortho), 170.43 (d, ³J_PC = 16.8 Hz, C=O), 171.89 (d, ²J_PC = 17.6 Hz, P-C=C), 176.59 (1C, C₉H₉N₂O).  ³¹P NMR (202.4 MHz, CDCl₃): δ 23.56 (Ph₃P⁺-C).

Minor isomer E-4b (32%): ¹H NMR (500.1 MHz, CDCl₃): δ 2.52(2H, m, H₂C-CO), 3.44(2H, m, H₂C-N), 3.74 and 3.79 (6H, 2s, 2OCH₃), 4.93 (1H_bro, P-C-CH), 6.99–7.71 (20H_arom, m, 4C₆H₅). ¹³C NMR (125.8 MHz, CDCl₃): δ 29.54 and 29.96 (2C, C₉H₉N₂O),  39.76 (d, ¹J_PC = 139.4 Hz, P=C), 52.01 and 52.27 (2s, 2OCH₃), 60.20 (d, ²J_PC = 15.2 Hz, P-C-CH), 116.52, 119.80, 123.07, 126.23 and 126.86 (5C, C₉H₉N₂O), 126.17 (d, ¹J_PC = 92.0 Hz, C_ipso), 128.60 (d, ³J_PC = 11.8 Hz, C_meta), 131.69 (C_para­),  132.15 (1C, C₉H₉N₂O), 133.64 (d, ²J_PC = 10.0 Hz, C_ortho), 172.02 (d, ³J_PC = 14.3 Hz, C=O), 171.74 (d, ²J_PC = 15.4 Hz,  P-C=C), 177.11 (1C, C₉H₉N₂O). ³¹P NMR (202.4 MHz, CDCl₃): δ 24.90 (Ph₃P⁺-C ).

Diethyl-2-(1-phenyl-3-pyrazolidinone-2-yl)-3-(triphenylphosphanylidene) butanedioate (4c).

White powder, m.p 161-163°C, 0.54g, yield 91%, IR (υ_max, cm^-1) 1748 and 1662  (C=O). MS (m/z, %): 502 (M-2OEt , 50), 434 (M-PPh and OEt, 28), 330 (M-PPh_3, 7),   262 (PPh_3, 85), 183 (PPh₂, 83), 108 (PPh, 31). Anal. calcd. for C₃₅H₃₅N₂O₅P (594): C, 71.35; H, 6.05; N, 4.64%. Found: C, 70.71; H, 5.95; N, 4.71%.

Major isomer Z-4c (66%):  ¹H NMR (500.1 MHz, CDCl₃): δ 0.36 and 1.27 (6H, 2t, ³J_HH = 7.0 Hz,  2OCH₂CH₃), 2.41(2H, m, H₂C-CO), 3.48 and 3.54 (4H, 2m, 2ABX₃ system, 2OCH₂CH₃), 3.59(2H, m, H₂C-N), 4.26 (1H_bro, P-C-CH), 7.12-7.73 (20H_arom, m, 4C₆H₅). ¹³C NMR (125.8 MHz, CDCl₃): δ 13.96 and 14.13 (2s, 2OCH₂CH₃), 29.61 and 30.09 (2C, C₉H₉N₂O), 37.89 (d, ¹J_PC = 128.9 Hz, P=C), 57.45 and 58.05 ( 2S, 2OCH₂CH₃), 59.98 (d, ²J_PC = 14.8 Hz, P-C-CH), 116.59, 119.80, 122.96, 126.35 and 127.08 (5C, C₉H₉N₂O),  126.27 (d, ¹J_PC = 92.0 Hz, C_ipso), 128.35 (d,  ³J_pc = 12.1 Hz, C_meta), 131.63 (C_para), 132.07 (1C, C₉H₉N₂O), 133.88 (C_ortho), 170.69 (d, ³J_PC = 17.7 Hz, C=O), 171.19 (d, . ²J_PC = 16.3 Hz, P-C=C), 176.99 (1C, C₉H₉N₂O).³¹P NMR (202.4 MHz, CDCl₃): δ 23.35 (Ph₃P⁺-C)

Minor isomer E-4c (34%): ¹H NMR (500.1 MHz, CDCl₃): δ 1.09 and 1.32 (6H, 2t, ³J_HH = 7.2 Hz , 2OCH₂CH₃), 2.53(2H, m, H₂C-CO), 3.41(2H, m, H₂C-N),  3.91 and 4.06 (4H, 2m, 2ABX₃ system, 2OCH₂CH₃), 4.31 (1H_bro, P-C-CH), 7.12-7.73 (20H_arom, m, 4C₆H₅). ¹³C NMR (125.8 MHz, CDCl₃): δ 14.13 and 14.73 (2s, 2OCH₂CH₃), 29,53 and 30.01 (2C, C₉H₉N₂O), 39.69 (d, ¹J_PC =133.3 Hz, P=C), 58.01 and 58.39 (2s, 2OCH₂CH₃),  60.41 (d, ²J_PC = 15.1 Hz, P-C-CH), 116.51, 120.05, 123.20, 126.42 and 127.15 (5C, C₉H₉N₂O), 126.72 (d, ¹J_PC=91.8 Hz, C_ipso), 128.54 (d, ³J_pc = 12.0 Hz, C_meta), 129.19 (1C, C₉H₉N₂O), 131.76 (C_para), 132.14 (1C, C₉H₉N₂O), 133.88 (C_ortho), 169.98 (d, ³J_PC =16.4 Hz, C=O), 170.12 (d, ²J_PC = 15.9 Hz, P-C=C),177.26 (1C, C₉H₉N₂O). ³¹P NMR (202.4 MHz, CDCl₃): δ 23.52 (Ph₃P⁺-C ).

Di-tert-buthyl-2-(1-phenyl-3-pyrazolidinone-2-yl)-3-(triphenylphosphanylidene) butanedioate (4d).

White crystals, m.p. 176-178 ºC, 0.62g, yield 96%; IR (νmax, cm-1): 1746 and 1671 (C=O). MS (m/z, %): 650 (M, 3), 386 (M-PPh₃, 38),  262 (PPh₃, 79), 183 (PPh₂, 43), 108 (PPh, 51). Anal. calcd. for C₃₉H₄₃N₂O₅P (650): C, 71.08; H, 6.72; N, 4.28%. Found: C, 71.56; H, 6.68; N, 4.31%.

Major rotamer Z-4d ¹H NMR (500.1 MHz, CDCl₃), δ_H 0.80 and 1.49 (18H, 2s, 2OCMe3), 2.50(2H, m, H₂C-CO), 3.46(2H, m, H₂C-N), 4.67 (1H, d, ³J_PH = 17.4 Hz, P-C-CH), 7.03-7.69 (20H_arom, m, 4C₆H₅). ¹³C NMR (125.8 MHz, CDCl₃), δ 28.16 and 28.43 (2OCMe₃), 29.76 and 30.12 (2C, C₉H₉N₂O), 37.63 (d, ¹J_PC = 127.2 Hz, P=C), 60.79 (d, ²J_PC =14.9 Hz, P-C-CH), 80.60 and 80.83 (2s, 2OCMe₃), 116.61, 119.36, 121.17, 122.75 and 123.66 (5C, C₉H₉N₂O), 127.18 (d, ¹J_PC = 91.2 Hz, C_ipso), 128.31 (d, ³J_PC = 11.8 Hz, C_meta), 131.56 (C_para), 132.22 (1C, C₉H₉N₂O), 133.82 (d, ²J_PC = 9.4 Hz, C_ortho), 169.98(d, ³J_PC = 11.6 Hz, C=O), 171.03 (d, ²J_PC = 11.7 Hz, P-C=C), 177.74 (1C, C₉H₉N₂O).  ³¹P NMR (202.4 MHz, CDCl₃): δ_P 23.29 (Ph₃P⁺-C).

Dimethyl -2-( 2,4-thiazolidinedione-2-yl)-3-(triphenylphosphanylidene) butaned- ioate (4e).

White crystals, m.p. 95-97 ºC, 0.48g, yield 94%; IR (νmax, cm-1): 1739 and 1685, 1662 and 1610 (C=O); MS, (m/z, %): 509 (M⁺, 1), 334 (M-C₃H₂O₂NS and CO₂Me, 29), 278 (M-3Ph, 69), 262 (PPh₃, 83), 183 (PPh₂, 86), 108 (PPh, 36). Anal. calcd. for C₂₇H₂₄NO₆PS (521): C, 62.17; H, 4.64; N, 2.69 %. Found: C, 62.28; H, 4.60; N, 2.65%.

Major rotamer Z-4e (63%): ¹H NMR (500.1 MHz, CDCl₃), δ_H 3.11 and 3.70 (6H, 2s, 2OCH₃), 3.75 (2H, dd, ²J_HH = 16.0, S-CH₂),  4.78 (1H, d, ³J_PH = 15.0 Hz, P-C-CH), 7.45-7.70 (15H_arom, m, 3C₆H₅); ¹³C NMR (125.8 MHz, CDCl₃), δ_C  32.98 (1C, S-CH₂), 36.33 (d, ¹J_PC = 131.1 Hz, P=C), 49.08 and 52.88 (2OCH₃), 58.96 (d, ²J_PC = 18.3 Hz, P-C-CH), 126.71 (d, ¹J_PC = 91.7 Hz, C_ipso), 128.87 (d, ³J_PC = 10.7 Hz, C_meta), 132.19 (C_para), 133.60 (d, ²J_PC = 9.8 Hz, C_ortho), 170.29 (d, ³J_PC = 12.3 Hz, C=O), 170.59 (d, ²J_PC = 17.6 Hz, P-C=C), 171.39 (1C, CH₂–CO), 172.01 (1C, S-CO);   ³¹P NMR (202.4 MHz, CDCl₃): δ_P 22.68 (Ph₃P⁺-C).

Minor rotamer E-4e (37%): ¹H NMR (500.1 MHz, CDCl₃), δ_H 3.58 and 3.69 (6H, 2s, 2OCH₃), 3.73 (2H, dd, ²J_HH = 16.1, S-CH₂), 4.81 (1H, d, ³J_PH = 15.9 Hz, P-C-CH), 7.45-7.70 (15H_arom, m, 3C₆H₅); ¹³C NMR (125.8 MHz, CDCl₃), δ_C 32.74 (1C, S-CH₂), 38.15 (d, ¹J_PC = 137.0 Hz, P=C), 50.53 and 52.64 (2 OCH₃), 58.54 (d, ²J_PC = 17.6 Hz, P-C-CH), 126.05 (d, ¹J_PC = 91.7 Hz, C_ipso), 128.51 (d, ³J_PC = 12.1 Hz, C_meta), 132.16 (C_para), 133.64 (d, ²J_PC = 9.7 Hz, C_ortho), 170.46 (d, ³J_PC = 17.5 Hz, C=O), 171.01 (d, ²J_PC = 18.7 Hz, P-C=C), 171.27 (1C, CH₂–CO), 172.05 (1C, S-CO);    ³¹P NMR (202.4 MHz, CDCl₃): δ_P 22.52 (Ph₃P⁺-C).

Diethyl -2-(2,4-thiazolidinedione-2-yl)- 3-(triphenylphosphanylidene) butaned- ioate (4f).

White crystals, m.p. 134-136 ºC, 0.49g, yield 91%; IR (ν_max, cm^-1): 1740, 1715, 1680 and 1636  (C=O). MS, (m/z, %): 391 (M-2CO₂Et, 53), 275 (M-PPh₃, 74), 262 (PPh₃, 74), 183 (PPh₂, 75), 108 (PPh, 37). Anal. calcd. for C₂₉H₂₈NO₆PS (549): C, 63.36; H, 5.14; N, 2.55 %. Found: C, 63.30; H, 5.21; N, 2.49%.

Major rotamer Z-4f (71%): ¹H NMR (500.1 MHz, CDCl₃), δ_H 0.44 and 1.26 (6H, 2t, ³J_HH = 6.8 Hz 2OCH₂CH₃), 3.68 (2H, dd, ²J_HH = 16.5 Hz, S-CH₂), 3.76 and 4.14 (4H, 2m, 2ABX₃ systhem 2OCH₂CH₃), 4.79 (1H, d, ³J_PH = 15.9 Hz, P-C-CH), 7.48-7.73 (15H_arom, m, 3C₆H₅); ¹³C NMR (125.8 MHz, CDCl₃), δ_C 14.12 and 14.33 (2s, 2OCH₂CH₃), 32.97 (1C, S-CH₂), 36.12 (d, ¹J_PC = 130.5 Hz, P=C), 57.62 and 59.14. ( 2S, 2OCH₂CH₃), 59.78 (d, ²J_PC = 18.2 Hz, P-C-CH), 126.42 (d, ¹J_PC =  91.8 Hz, C_ipso), 128.73 (d, ³J_PC = 11.2 Hz, C_meta), 132.09 (C_para), 133.64 (C_ortho), 168.39 (d, ³J_PC = 12.4 Hz, C=O), 169.77 (d, ²J_PC = 11.6 Hz, P-C=C), 170.60 (1C, CH₂–CO), 170.67 (1C, S-CO); ³¹P NMR (202.4 MHz, CDCl₃): δ_P 22.66 (Ph₃P⁺-C).

Minor rotamer E-4f (29%): ¹H NMR (500.1 MHz, CDCl₃), δ_H 1.18 and 1.30 (6H, 2t, ³J_HH = 7.2 Hz, 2OCH₂CH₃), 3.74 (2H, dd, ²J_HH = 16.3 Hz, S-CH₂),  4.04 and 4.24 (4H, 2m, 2ABX₃systhem 2OCH₂CH₃), 4.77 (1H, d, ³J_PH = 18.0 Hz, P-C-CH), 7.48-7.73 (15H_arom, m, 3C₆H₅); ¹³C NMR (125.8 MHz, CDCl₃), δ_C 13.88 and 13.91 (2s, 2OCH₂CH₃), 32.86 (1C, S-CH₂), 38.04 (d, ¹J_PC = 138.8 Hz, P=C), 57.67 and 59.36 (2s, 2OCH₂CH₃),  59.94 (d, ²J_PC = 17.0 Hz, P-C-CH), 126.37 (d, ¹J_PC = 92.1 Hz, C_ipso), 128.50 (d, ³J_PC = 12.1 Hz, C_meta), 132.14 (C_para), 133.60 (C_ortho), 168.48 (d, ³J_PC = 12.7 Hz, C=O), 169.67 (d, ²J_PC = 14.8 Hz, P-C=C), 170.45 (1C, CH₂–CO), 170.85 (1C, S-CO);  ³¹P NMR (202.4 MHz, CDCl₃): δ_P 22.71 (Ph₃P⁺-C).

Di-tert-buthyl-2-(2,4-thiazolidinedione-1-yl)-3-(triphenylphosphanylidene) butanedioate (4g).

White crystals, m.p. 133-135 ºC, 0.58g, yield 96%; IR (νmax, cm-1): 1737, 1729, 1665 and 1639 (C=O). ). MS, (m/z, %): 343 (M-PPh₃, 9), 276 (M-PPh₂ and 2OCMe_3,38 ), 262 (PPh₃, 75), 227 (M-PPh₃ and C₃H₂O₂NS, 6), 183 (PPh₂, 63), 108 (PPh, 26). Anal. calcd. for C₃₃H₃₆NO₆PS (605): C, 65.42; H, 5.99; N, 2.31 %. Found: C, 65.51; H, 6.05; N, 2.35%.

Major rotamer Z-4g : 1H NMR (500.1 MHz, CDCl₃), δ_H 0.94 and 1.54 (18H, 2s, 2OCMe3), 3.72 (2H, dd, ²J_HH = 16.9 Hz, S-CH₂), 4.62 (1H, d, ³J_PH = 17.3 Hz, P-C-CH), 7.48-7.75 (15H_arom, m, 3C₆H₅); ¹³C NMR (125.8 MHz, CDCl₃), δ_C 28.32 and 28.37 (2OCMe₃), 32.82 (1C, S-CH₂), 36.13 (d, ¹J_PC = 130.8 Hz, P=C), 60.54 (d, ²J_PC = 17.9 Hz, P-C-CH), 77.17 and 81.26 (2s, 2OCMe₃), 127.51 (d, ¹J_PC = 91.7 Hz, C_ipso), 128.64 (d, ³J_PC = 11.7 Hz, C_meta), 132.01(C_para), 133.64 (d, ²J_PC = 9.8 Hz, C_ortho), 167.68 (d, ³J_PC = 12.6 Hz, C=O), 168.66 (d, ²J_PC=13.3 Hz, P-C=C), 169.82 (1C, CH₂–CO), 170.74 (1C, S-CO);  ³¹P NMR (202.4 MHz, CDCl₃): δ_P 23.15 (Ph₃P⁺-C).

Dimethyl 2-(rhodanine-1-yl)-3-(triphenylphosphanylidene) butanedioate (4h).

white crystals, m.p 108-110 °C, 0.48 g , yield 90 % . IR (KBr) (v_max, cm^-1): 1722, 1747 and 1623 (C=O). MS, (m/z, %): 537 (M⁺, 6), 475 (M-2OCH₃, 52), 419 (M-2CO₂CH₃, 36), 262 (PPh₃, 85), 183 (PPh₂, 61), 120 (C₃H₂NOS₂, 29), 108 (PPh, 44), Anal. calcd. for C₂₇H₂₄NO₅PS₂ (537): C, 60.31; H, 4.50; N, 2.67 %. Found: C, 60.25; H, 4.58; N, 2.75%.

Major isomer Z-4h (66%): ¹H NMR (500.1 MHz, CDCl₃): δ 3.07 and 3.69 (6H, 2s, 2OCH₃), 3.83 (2H, s, S-CH₂), 5.39 (1H, d, ³J_PH = 14.4 Hz, P=C-CH), 7.47-7.72 (15Haro, m, 3C₆H₅). ¹³C NMR (125.8 MHz, CDCl₃): δ 33.90 (1C, S-CH₂), 43.50 (d, ¹J_PC = 126.2 Hz, P=C), 49.34 and 52.30 (2s, 2OCH₃), 63.25 (d, ²J_PC = 15.7 Hz, P-C-CH), 126.30 (d, ¹J_PC = 92.1 Hz, C_ipso), 128.57 (d, ³J_PC = 12.2 Hz, C_meta), 132.01 (d, ⁴J_PC = 2.2 Hz,  C_para), 133.47 (d, ²J_PC = 8.9 Hz, C_ortho), 165.4 (C=O), 170.60 (1C, CH₂–CO), 170.69 (1C, S-CS); 171.59 (d, ²J_PC = 12.5 Hz, P-C=C). ³¹P NMR (202.4 MHz, CDCl₃): δ 22.50 (Ph₃P⁺-C).

Minor isomer E-4h. (34%): ¹H NMR (500.1 MHz, CDCl₃): δ 3.60 and 3.71 (6H, 2s, 2OCH₃), 3.81 (2H, s, S-CH₂), 5.51 (1H, d, ³J_PH = 17.4 Hz, P=C-CH), 7.47-7.72 (15Haro, m, 3C₆H₅). ¹³C NMR (125.8 MHz, CDCl₃): δ 33.97 (1C, S-CH₂), 45.09 (d, ¹J_PC =137.3 Hz, P=C), 51.36 and 52.47 (2s, 2OCH₃), 63.78 (d, ²J_PC = 15.9 Hz, P-C-CH), 125.86 (d, ¹J_PC=92.0 Hz, C_ipso), 128.90 (d, ³J_PC = 12.0 Hz, C_meta), 132.29 (d, ⁴J_PC =  2.4 Hz, C_para), 133.59 (d, ²J_PC = 9.8 Hz, C_ortho), 165.7 (C=O), 169.83 (d, ²J_PC = 12.3 Hz, P-C=C). 170.96 (1C, CH₂–CO), 171.16 (1C, S-CS); ³¹P NMR (202.4 MHz, CDCl₃): δ 22.42 (Ph₃P⁺-C ).

Di-tert-butyl 2-(rhodanine-1-yl)-3-(triphenylphosphanylidene) butanedioate (4i).

White crystals, m.p 157-159 ºC, 0.58 g, yield 93 % . IR (v_max, cm^-1): 1726, 1638 (C=O). MS, (m/z, %): 621 (M⁺, 5), 507 (M-2CMe₃, 34), 475 (M⁺-2OCMe₃, 49), 262 (PPh₃, 85), 183 (PPh₂, 60), 108 (PPh, 51), Anal. calcd. for C₃₃H₃₆NO₅PS₂ (621): C, 63.74; H, 5.84; N, 2.30 %. Found: C, 63.80; H, 5.91; N, 2.26%.

Major isomer Z-4i (87%): ¹H NMR (500.1 MHz, CDCl₃), δ 1.28 and 1.39 (18H, 2s, 2CMe₃), 3.73 (2H, d, S-CH₂), 4.63 (1H, d, ³J_PH = 16.6 Hz, P-C-CH), 7.27-7.73 (15Haro, m, 3C₆H₅). ¹³C NMR (125.8 MHz, CDCl₃), δ 28.25 and 28.48 (2s, 2CMe₃), 34.12 (1C, S-CH₂), 40.92 (d, ¹J_PC =126.9 Hz, P=C), 64.33 (d, ²J_PC = 14.7 Hz, P-C-CH), 77.92 and 80.43 (2s, 2OCMe₃), 127.84 (d, ¹J_PC = 91. 6 Hz, C_ipso), 128.31 (d, ³J_PC = 12.2 Hz, C_meta), 131.70 (C_para), 133.99 (d, ²J_PC = 9.7 Hz, C_ortho), 167.85 (d, ³J_PC =12.2 Hz, C=O), 170.06 (d, ²J_PC =13.8 Hz, P-C=C). 171.63 (1C, CH₂–CO), 171.97 (1C, S-CS); ³¹P NMR (202.4 MHz, CDCl₃): δ 22.09 (Ph₃P⁺-C).

Dimetyl-2-( 4,5,6,7-tetrahydroindazole-1-yl)-3-(triphenylphosphanylidene) butanedioate (4j).

white crystals, m.p 154-156°C, 0.45 g, yield 87 % . IR(KBr) (v_max, cm^-1): 1753 and 1636 (2C=O). MS (m/z, %): 526 (M⁺, 6), 501 (M⁺-CO₂Me, 7), 467 (M⁺-CO₂CH₃,100), 405(M⁺-C₇H₉N₂,65), 262 (PPh₃, 80), 183 (PPh₂, 100), 108 (PPh, 40), 77 (Ph, 15), 59 (CO₂Me, 7). Anal. calcd. for C₃₁H₃₁N₂O₅P (526): C, 70.69; H, 5.94; N, 5.32 %. Found: C, 70.63; H, 5.98; N, 5.38%.

Major isomer Z-4j (52%): ¹H NMR (500.1 MHz, CDCl₃): δ 1.73 and 2.68 (8H, m, 4CH₂), 3.14 and 3.72 (6H, 2s, 2OCH₃), 4.90 (1H, d, ³J_PH = 16.7 Hz, P=C-CH), 7.45-7.72 (16Haro, m, 3C₆H₅ and C₇H₉N₂). ¹³C NMR (125.8 MHz, CDCl₃): 20.87, 23.23 and 23.54 (4 CH₂), 43.72 (d, ¹J_PC = 128.2 Hz, P=C), 49.26 and 52.35 (2s, 2OCH₃), 64.54 (d, ²J_PC = 15.0 Hz, P=C-CH), 115.45 (1C, N-C=C), 126.44 (d, ¹J_PC = 92.9 Hz, C_ipso), 128.49 (d, ³J_PC = 12.1 Hz, C_meta), 131.92 (C_para), 133.40 (1C, N-N=C), 133.64 (d, ²J_PC = 9.9 Hz, C_ortho), 146.90 (1C, N-C=C), 165.37 (C=O), 172.59 (d, ²J_PC = 13.0 Hz, P-C=C). ³¹P NMR (202.4 MHz, CDCl₃): δ 24.18 (Ph₃P⁺-C).

Minor isomer E-4j (48%): ¹H NMR (500.1 MHz, CDCl₃): δ 1.73 and 2.68 (8H, m, 4CH₂), 3.61 and 3.72 (6H, 2s, 2OCH₃), 4.93 (1H, d, ³J_PH = 18.3 Hz, P=C-CH), 7.45-7.72 (16H, m, 3C₆H₅ and C₇H₉N₂). ¹³C NMR (125.8 MHz, CDCl₃): 21.94, 22.90 and 23.63 (4 CH₂), 43.94 (d, ¹J_PC = 133.8 Hz, P=C), 52.22 and 52.53 (2s, 2OCH₃), 63.93 (d, ²J_PC = 16.3 Hz, P=C-CH), 115.13 (1C, N-C=C), 125.93 (d, ¹J_PC = 82.4 Hz, C_ipso), 128.81 (d, ³J_PC =  12.3 Hz, C_meta), 131.92 (C_para), 133.19 (1C, N-N=C), 133.64 (d, ²J_PC = 9.9 Hz, C_ortho), 147.43 (1C, N-C=C), 165.68 (C=O), 169.78 (d, ²J_PC = 12.1 Hz, P-C=C), ³¹P NMR (202.4 MHz, CDCl₃): δ 23.06 (Ph₃P⁺-C ).

Dimethyl 2-(3-methylpyrazole-1-yl)-3-(triphenylphosphanylidene) butanedioate (4k).

White powder, m.p 183-144°C, 0.46 g, yield 94%, IR (v_max, cm^-1): 1755 and 1638 (C=O). MS (m/z, %): 486 (M⁺, 9), 423 (M⁺-CO₂Me, 100), 405 (M⁺-C₄H₅N₂, 22), 262 (PPh₃, 35), 183 (PPh₂, 50), 108 (PPh, 20), 77 (Ph, 8). Anal. calcd. for C₂₈H₂₇N₂O₄P (486): C, 69.11; H, 5.60; N, 5.76 %. Found: C, 68.97; H, 5.65; N, 5.80 %.

Major isomer Z-4k (55%): ¹H NMR (500.1 MHz, CDCl₃): δ 2.17 (3H, s, CH₃), 3.20 and 3.72 (6H, 2s, 2OCH₃), 4.91 (1H, d, ³J_PH = 16.6 Hz, P=C-CH), 7.28-7.95 (17Haro, m, 3C₆H₅ and C₄H₅N₂). ¹³C NMR (125.8 MHz, CDCl₃): δ 13.52 (s, CH₃), 43.76 (d, ¹J_PC = 127.7 Hz, P=C), 49.34 and 52.30 (2s, 2OCH₃), 64.52 (d, ²J_PC = 15.9 Hz, P-C-CH), 104.97 (1C, C₄H₅N₂), 126.30 (d, ¹J_PC = 92.1 Hz, C_ipso), 128.57 (d, ³J_PC = 12.2 Hz, C_meta), 132.01 (d, ⁴J_PC = 2.2 Hz,  C_para), 132.13 (1C, C₄H₄N₂), 133.47 (d, ²J_PC = 8.9 Hz, C_ortho), 146.50 (N-N=C), 165.4 (C=O), 172.50 (d, ²J_PC =12.6 Hz, P-C=C). ³¹P NMR (202.4 MHz, CDCl₃): δ 24.08 (Ph₃P⁺-C).

Minor isomer E-4k (45%): ¹H NMR (500.1 MHz, CDCl₃): δ 2.20 (3H, s, CH₃), 3.61 and 3.71(6H, 2s, 2OCH₃), 4.95 (1H, d, ³J_PH = 18.2 Hz, P=C-CH), 7.28-7.95 (17Haro, m, 3C₆H₅ and C₄H₅N₂). ¹³C NMR (125.8 MHz, CDCl₃): δ 11,98 (s, CH₃), 44.04 (d, ¹J_PC = 138.0 Hz, P=C), 50.32 and 52.32 (2s, 2OCH₃), 63.57 (d, ²J_PC = 15.8 Hz, P-C-CH), 104.77 (1C, C₄H₅N₂), 125.67 (d, ¹J_PC = 92.2 Hz, C_ipso), 128.84 (d, ³J_PC = 12.1 Hz, C_meta), 132.13 (1C, C₄H₅N₂), 132.29 (d, ⁴J_PC = 2.4 Hz, C_para), 133.59 (d, ²J_PC = 9.8 Hz, C_ortho), 147.00 (N-N=C), 165.7 (C=O), 169.83 (d, ²J_PC = 12.3 Hz, P-C=C). ³¹P NMR (202.4 MHz, CDCl₃): δ 24.84 (Ph₃P⁺-C ).

Diethyl 2-(3-methylpyrazole-1-yl)-3-(triphenylphosphanylidene) butanedioate (4l).

white crystals, m.p 147-149°C, 0.47 g , yield 92% . IR(KBr) (v_max, cm^-1): 1757 and 1635 (C=O). MS (m/z, %): 514 (M⁺, 3), 441 (M⁺-CO₂Et, 100), 262 (PPh₃, 42), 183 (PPh₂, 44), 108 (PPh, 21), 77 (Ph, 8). Anal. calcd. for C₃₀H₃₁N₂O₄P (514): C, 70.00; H, 6.08; N, 5.44 %. Found: C, 70.38; H, 6.13; N, 5.49 %.

Major isomer Z-4l (63%): ¹H NMR (500.1 MHz, CDCl₃): δ 0.48 and 1.23 (6H, 2t, ³J_HH = 7.1Hz, 2OCH₂CH₃), 2.17 (3H, s, CH₃), 3.75 and 4.10 (4H, 2m, 2ABX₃ system, 2OCH₂CH₃), 4.90 (1H, d, ³J_PH = 16.8 Hz, P-C-CH), 7.20-7.97 (17Haro, m, 3C₆H₅ and C₄H₅N₂). ¹³C NMR (125.8 MHz, CDCl₃): 13.56 (s, CH₃) 13.56 and 14.21 (2OCH₂CH₃), 43.40 (d, ¹J_PC = 127.6 Hz, P=C), 57.75 and 61.09 (2s, 2OCH₂CH₃), 64.53 (d, ²J_PC = 16.6 Hz, P-C-CH), 104.80 (1C, C₄H₅N₂), 126.62 (d, ¹J_PC = 92.1 Hz, C_ipso), 128.70 (d, ³J_PC = 12.1 Hz, C_meta), 132.21 (C_para), 133.61 (d, ²J_PC = 9.8 Hz, C_ortho), 133.67 (1C, C₄H₅N₂), 146.13 (1C, N-N=C), 169.21 (d, ³J_PC = 12.8 Hz,C=O), 171.68 (d, ²J_PC = 12.3 Hz, P-C=C). ³¹P NMR (202.4 MHz, CDCl₃): δ 24.09 (Ph₃P⁺-C).

Minor isomer E-4l (37%):  ¹H NMR (500.1 MHz, CDCl₃): δ 1.18 and 1.30 (6H, 2t, ³J_HH=7.1 Hz, 2OCH₂CH₃), 2.20 (3H, s, CH₃), 4.75 and 4.20 (4H, 2m, 2ABX₃system, 2OCH₂CH₃), 4.91 (1H, d, ³J_PH = 18.1 Hz, P-C-CH), 7.20-7.97 (17Haro, m, 3C₆H₅ and C₄H₅N₂). ¹³C NMR (125.8 MHz, CDCl₃): 13.11 (s, CH₃), 13.99 and 14.84 (2OCH₂CH₃), 43.85 (d, ¹J_PC = 135.6 Hz, P=C), 58.39 and 61.09 (2s, 2OCH₂CH₃), 63.86 (d, ²J_PC = 16.3 Hz, P-C-CH), 104.64 (1C, C₄H₅N₂), 125.96 (d, ¹J_PC = 92.7 Hz, C_ipso), 128.70 (d, ³J_PC = 12.1 Hz, C_meta), 132.21 (C_para), 133.61 (d, ²J_PC = 9.8 Hz, C_ortho), 133.67 (1C, C₄H₅N₂), 146.61 (1C, N-N=C), 169.99 (d, ³J_PC = 12.8 Hz,C=O), 171.53 (d, ²J_PC = 10.6 Hz, P-C=C). ³¹P NMR (202.4 MHz, CDCl₃): δ 24. 95 (Ph₃P⁺-C).

Di-tert-butyl 2-(3-methylpyrazole-1-yl)-3-(triphenylphosphanylidene) butanedioate (4m).

White crystals, m.p 175-177 ºC, 0.55 g, yield 96% . IR (v_max, cm^-1): 1749, 1642 (C=O). MS, (m/z, %): 570 (M⁺, 10), 469 (M⁺-CO₂CMe₃, 65), 287 (M⁺– PPh₃-C-CH,85), 262 (PPh₃, 50), 183 (PPh₂, 55), 108 (PPh, 23), 77 (Ph, 5), 57 (CMe₃, 33). Anal. calcd. for C₃₄H₃₉N₂O₄P (570): C, 71.54; H, 6.89; N, 4.91 %. Found: C, 71.60; H, 6.92; N, 4.89 %.

Major isomer Z-4m (57%): ¹H NMR (500.1 MHz, CDCl₃), δ 0.95 and 1.50 (18H, 2s, 2CMe₃), 2.15 (3H, s, CH₃), 4.96 (1H, d, ³J_PH = 17.3 Hz, P-C-CH), 6.60-8.00 (17Haro, m, 3C₆H₅ and C₄H₅N₂). ¹³C NMR (125.8 MHz, CDCl₃), δ 13.56 (s, CH₃), 28.18 and 28.37 (2s, 2CMe₃), 43.21 (d, ¹J_PC = 127.1 Hz, P=C), 65.24 (d, ²J_PC = 16.74 Hz, P-C-CH), 77.89 and 80.54 (2s, 2OCMe₃), 104.68 (1C, C₄H₅N₂), 127.4 (d, ¹J_PC = 92.0 Hz, C_ipso), 128.51 (d, ³J_PC = 12.3 Hz, C_meta), 132.00 (C_para), 133.71 (d, ²J_PC = 9.6 Hz, C_ortho), 145.85 (1C, C₄H₅N₂), 168.65 (d, ³J_PC = 12.2 Hz, C=O), 170.39 (d, ²J_PC = 13.3 Hz, P-C=C). ³¹P NMR (202.4 MHz, CDCl₃): δ 24.91 (Ph₃P⁺-C).

Minor isomer E-4m (43%): ¹H NMR (500.1 MHz, CDCl₃), δ 1.46 and 1.48 (18H, 2s, 2CMe₃), 2.18 (3H, s, CH₃), 4.99 (1H, d, ³J_PH = 16.9 Hz, P-C-CH), 6.60-8.00 (17Haro, m, 3C₆H₅ and C₄H₅N₂). ¹³C NMR (125.8 MHz, CDCl₃), δ 11.01 (s, CH₃), 28.12 and 28.45 (2s, 2CMe₃), 43.55 (d, ¹J_PC = 138.1 Hz, P=C), 64.20 (d, ²J_PC =15.08 Hz, P-C-CH), 77.93 and 80.42 (2s, 2OCMe₃), 104.39 (1C, C₄H₅N₂), 127.27 (d, ¹J_PC = 92.1 Hz, C_ipso), 128.51 (d, ³J_PC = 12.3 Hz, C_meta), 132.00 (C_para), 133.93 (d, ²J_PC = 9.8 Hz, C_ortho), 146.41 (1C, C₄H₅N₂), 168.65 (d, ³J_PC = 12.2 Hz, C=O), 170.39 (d, ²J_PC = 13.3 Hz,P-C=C). ³¹P NMR (202.4 MHz, CDCl₃): δ 24.47(Ph₃P⁺-C).

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