Reaction of alpha;-metallatedN-acyl-lambda;5-phosphazenes with aryl cyanides

摘要

J. CHEM. SOC. PERKIN TRANS. I 1989 615 Reaction of a-MetaIIated N-Acyl-h5-Phosphazenes with Aryl Cyanides Jose Barluenga," Miguel Ferrero, Fernando Lopez, and Francisco Palacios Departamento de Quimica Organometalica, Universidad de Oviedo, 3307 1 Oviedo, Spain Metallated N-acyl-h5-phosphazenes react with aryl cyanide to give imino-h5-phosphazenes (6) and (7), inwhich nitrile insertion into the phosphorus-carbon bondof N-acyl-h5-phosphazenes (2) and (3)takes place. Subsequent reactions of the imino-and enamino-N-ethoxycarbonyl-h5-phosphazenes (7) and (9) afford the phosphine oxide derivatives (I 3)and (I I), through a cyclocondensation and hydrolysis sequence. h5-Phosphazenes were first prepared in 1919.' Applications of these species have attracted growing interest in recent years because of their widespread utility; i.e., as organic semi-conductors,2 as backbone polymer prec~rsors,~ and as ligands in transition-metal complexes;4 they have also been used in natural product and phosphorus-containing heterocycle synthesis.However, most reactions of these compounds involve the phosphorus-nitrogen double b~nd.~.~ Previously, we have reported on the the ability of a-metallated N-aryl-h'-phosphazenes to react with electrophiles, affording acyclic and heterocyclic * derivatives. In this context, C-functionalised h5-phosphazenes are valuable intermediates in organic synthe~is.~~' However, though a new synthetic method for N-functionalised h5-phosphazenes was recently reported,' ' very little is known about their reactivity.Continuing our interest in the chemistry of As-phosphazenes, we describe here the reaction of a-metallated N-acyl derivatives with aryl cyanides. Results and Discussion Primary (Z)-j3-enamino-h5-phosphazenes (5) were obtained through a-lithiation of N-aryl derivatives (1) followed by reaction with nit rile^,^ in a similar way to that recently reported for reactions of metallated 1,3-dithianes.I2 However, h5-phos- phazenes with electron-withdrawing substituents (2)and (3), obtained through the classical Staudinger reaction ' using alkyldiphenylphosphines and N-acyl azides in ether, show different reactivity. Thus, when compounds (2) and (3) were treated with lithium di-isopropylamide (LDA) followed by addition of aryl cyanides and aqueous work-up, j3-enamino compounds (8) and (9) were not obtained, but imino-h5- phosphazenes (6) and (7) were isolated instead (see Table and Scheme 1).The decreasing P-H and P-C coupling constants13 for the methyl group observed in the 'H and 13C n.m.r. spectra of (6a) (4JpH1.6 Hz, 3Jpc 13.8 Hz) relative to those of the starting N-benzoyl-h5-phosphazene (2a) (2JpH13.2 Hz, 'Jpc 63 Hz), is consistent with a shift of the methyl group from the a-to the y-position with respect to the phosphorus atom and, thus, with nitrile insertion into the phosphorus-carbon single bond. The isolation of the fragmentation products of (6a) (aminodiphenyl-phosphine oxide, acetophenone, and benzamide) by acid hydrolysis confirmed the structure of compounds (6).In the case of P-benzyl N-acyl derivatives (2b)and (3c) (R = Ph), however, no reaction products were observed, probably due to the lower reactivity of the corresponding anion.2MH So(6a) 4Ph,PONH, + PhCONH, + PhCOMe XR (2b) COPh Ph (3~1C02Et Ph These results could be explained through rearrangement l4 of the metallated intermediate (4), which probably involves formation of an unstable cyclic adduct ' containing pentavalent phosphorus, to give product (6) after treatment with water. The conjugation of electron-withdrawing substituents on h5-phos- phazenes (X = COPh, C0,Et) could stabilise the proposed intermediates. This new behaviour observed in h'-phosphazenes allows the isolation of new imino-h5-phosphazene species resulting from nitrile insertion into acyclic phosphorussarbon single bonds. A related reaction has been previously reported involving cyclic phosphine oxides.14 Primary (Z)-p-enamines derived from N-acyl-h5-phos-phazenes (8) and (9) are not available from a-metallated Table.N-Acyl-AS-phosphazenes(2) and (3) and rearrangement products (6) and (7) Compound R Ar Y Isolated yields. Yield (%)" M.p. ("C) 94 95-96 95 138-139 93 76-77 96 80-8 1 93 95-96 78 1 32-1 3 3 80 184-185 83 183-1 84 82 125-126 76 117-1 18 616 J. CHEM. SOC. PERKIN TRANS. I 1989 1 *Rx%N/x X=Ph... Ar N H I Ph, 'NH2 (9) OEt H X R (11 Ph (Za) COPh H (30)CO2Et H (3bl COzEt Me Scheme 1.Reagents and conditions: i, LDA-THF, -70 "C; ii, ArCN; iii, water; iv, LiAIH,-THF; v, N,COY&her compounds (2) and (3) with nitriles, but they were prepared by lithium aluminium hydride (LAH) reduction of intermediate (5) followed by treatment with acyl a~ides.~ Spectral data of compounds (8) are markedly different from those observed for the isomer (6b). Thus, in the IH n.m.r. spectrum, the vinyl hydrogen of (8) resonates at 6 4.31as a doublet with a coupling constant of 17.3 Hz, while the I3C n.m.r. spectrum shows an absorption at 73.0 (lJPc 107.1 Hz) assignable to the carbon bonded to phosphorus. These values are similar to those pre- The C,-hydrogen of the imino moiety is known to be labile towards Lewis acids l6 and, therefore, cyclocondensation of imino-1'-phosphazenes (7)by means of aluminium chloride was also attempted.Thus, the reaction of compound (7a) with aluminium chloride and aqueous work-up gave the amino phosphine oxide derivative (13), resulting probably by electrocyclisation process of the A1C1,-imino-h5-phosphazene complex followed by hydrolysis of the cyclic compound (12) (Scheme 3). viously reported for primary P-enamin~-h~-phosphazenes.~~~ The multifunctional character of N-ethoxycarbonyl p-enamino-h5-phosphazenes (9) was shown by thermal intra- molecular cyclocondensation under anhydrous conditions to give 1,3,4-diaza-h5-phosphinin-2-ones(10). However, the treatment of compounds (9) with base (KH) at 60 "C followed by methanolysis and aqueous work-up afforded the corre-sponding acyclic phosphine oxide (11).This result suggests that the cyclic derivative (10) undergoes hydrolysis under the reaction conditions, leading to (11); in fact, reaction of compound (10) with KH under similar reaction conditions afforded the product (11) (Scheme 2). 'c Scheme 2. Reagents and conditions: i, 150 "C; ii, KH-THF, 60 "C; iii, MeOH-water L (12 1I ii A (13) Scheme 3. Reagents and conditions: i, AIC1,-THF, 80 "C; ii, water In conclusion, we have shown that aryl cyanides were inserted into the phosphorus-carbon single bond of or-metallated N-acyl- 3L5-phosphazenes. This method allowed us to obtain imino-1'- phosphazenes for the first time, to the best of our knowledge.It is also worth noting that phosphorylated imines show oncolitic activity.' On the other hand, the multifunctional character of C-and N-functionalised h5-phosphazenes is reported. Thus, intramolecular cyclisation of P-imino and P-enamino-1'-phosphazenes (7)and (9) affords the acyclic phosphine oxide isomers (13) and (11) respectively. J. CHEM. SOC. PERKIN TRANS. I 1989 Experimental General.-M.p.s were taken on samples in open capillary tubes using a Buchi melting-point apparatus and are un-corrected. N.m.r. spectra were obtained using a Varian FT-80 n.m.r. spectrometer with deuteriated chloroform as solvent; chemical shifts are reported in p.p.m. downfield from internal SiMe, for 'H and 13C n.m.r. or from H$04 85% in the case of ,'P n.m.r.1.r. spectra were recorded in KBr on a Perkin-Elmer 298 spectrophotometer. Microanalyses were performed on a Perkin-Elmer model 240 instrument and mass spectra were obtained using a Hewlett-Packard 593014 spectrometer. Com- pounds (5) and (9) were obtained according to the literature method^.^,^ Synthesis of N-Acyl Alkyldiphenyl-h5-phosphazenes (2) and (3). General Procedure.-N-Benzoyl-P-methyldiphenyl-h'-phos-phazene (2a). In a dried, argon-filled round-bottomed flask, a solution of benzoyl azide (2.9 g, 20 mmol) in dry ether was added dropwise to a cooled (0 "C) solution of methyldiphenyl phos- phine (20 mmol) in ether. After being stirred for 1 h, the mixture was left to reach room temperature and was then stirred until N, evolution ceased.The solvent was evaporated off and the resulting oil was taken up in ether (10 ml) until formation of a crystalline solid, which was recrystallised from hexane-methyl- ene dichloride to give compound (2a) (6.0 g, 9473, m.p. 95-96 "C (Found: C, 74.9; H, 5.6; N, 4.2. C,oHl,NOP requires C, 75.22; H, 5.68; N, 4.39%); vma,.(KBr)1340 (P=N) and 1610 cm-' (Ca); G,(CDCl,) 2.31 (3 H, d 'JpH13.2 Hz, Me) and 7.12-8.31 (15 H, m, Ph); Gc(CDC13) 11.4 (d, 'JPc63.0 Hz, Me), 125.5-137.7 (Carom.),and 175.8 (CO); G,(CDCl,) 21.5. N-Benzoyl-P-benzyldiphenyl-h'-phosphazene(2b). M.p. 138-139 "C (Found: C, 79.1; H, 5.8; N, 3.7. C,,H,,NOP requires C, 78.97; H, 5.61; N, 3.54%); vma,.(KBr)1 340 (P=N) and 1600 cm-' (C=O); GH(CDC1,) 4.22 (2 H, d, ,JPH14.1 Hz, CH,) and 6.81-8.35 (20 H, m, Ph); G,(CDCl,) 31.7 (d, lJPc 51.2 Hz, CH,), 125.6-138.4 (Carom.),and 177.3 (CO); G,(CDC13) 27.2.N-Ethoxycarbonyl-P-methyldiphenyl-h5-phosphazene(3a). M.p. 76-77 "C (Found: C, 66.7; H, 6.2; N, 4.7. C,,H,,NO,P requires C, 66.89; H, 6.31; N, 4.87%); vma,.(KBr)1 280 (P=N) and 1 620 Cm-' (c=o); GH(CDC13) 1.22 (3 H, t, ,JHH 6.9 HZ, Me), 2.20 (3 H, d, *JPH13.2 Hz, Me), 4.0 (2 H, q, CH,), and 7.24 -7.84 (10 H, m, Ph); G,(CDCl,) 10.9 (d, 'JPc65.4 Hz, Me), 13.0 (Me),58.8 (d, 4Jpc3.3Hz, CH,), 125.2-130.3 (Carom.),and 160.5 (CO); G,(CDCl,) 22.5. N-Ethoxycarbonyl-P-ethyldiphenyl-L'-phosphazene (3b). M.p. 80-81 "C (Found: C, 67.6; H, 6.5; N, 4.6. C17H2,N0,P requires C, 67.76; H, 6.69; N, 4.65%); vma,.(KBr)1280 (P=N) and 1 590 cm-' (Ca); GH(CDC13) 1.14 (3 H, dt, ,JPH15.7 Hz, ,JHH7.9 Hz, Me), 1.24 (3 H, t, ,JHH6.9 Hz, Me), 2.63 (2 H, dd, ,JPH12.6 Hz, ,JHH7.9 Hz, CH,), and 7.24-7.87 (10 H, m, Ph); Gc(CDC1,) 4.5 (Me), 13.6 (Me), 17.7 (d, 'Jpc63 Hz, CH,), 59.6 (d, 4Jpc2.6 Hz, OCH,), 126.7-130.8 (Carom.),and 161.0 (CO); Gp(CDC1,) 28.2.P-Benzyldiphenyl-N-ethoxycarbonyl-h5-phosphazene (3c). M.p. 95-96 "C (Found: C, 72.5; H, 5.9; N, 3.8. C,,H,,NO,P requires C, 72.72; H, 6.10; N, 3.85%); vma,.(KBr)1280 (P=N) and 1 600 cm-' (c=o); G"(CDC1,) 1.26 (3 H, t, ,JHH6.9 Hz, Me), 4.08 (2 H, q, CH,), 4.20 (2 H, d, ,JPH13.2 Hz, CH,), and 6.67-7.89 (15 H, m, Ph); G,(CDCl,) 13.6 (Me), 31.3 (d, lJPc53.5 Hz, CH,), 59.7 (d, 4Jpc2.1 Hz, OCH,), 123.6-130.9 (Carom.),and 161.0 (CO); S,(CDCl,) 23.9.Synthesisof N-Acyl-P-iminodiphenyl-L5-phosphazenes(6) and (7). General Pvocedure.-l-Benzoyl-2,2,4-triphenyl-l,3-diaza-2h'-phosphupenta-1 ,3-diene (6a). In a dried, argon-filled round- bottomed flask, a solution of N-benzoyl-P-methyldipheny1-h'-phosphazene (2a) (1.6 g, 5 mmol) in tetrahydrofuran (THF) (20 ml) was added to a solution of LDA (5 mmol) in THF at -20 "C and the mixture was stirred for 0.5 h. The reaction mix- ture was cooled at -70 "C and then a solution of benzonitrile (5 mmol) in THF (10 ml) was added. When the mixture had attained room temperature it was stirred for 12 h and then poured into ice-water, extracted with methylene dichloride (100 ml), and the extract was dried (Na,SO,).Evaporation of the solvent afforded a crude solid, which was recrystallised from hexane-CH,Cl, to yield compound(6a) (1.6 g, 78%), m.p. 132-133 "C (Found: C, 76.5; H, 5.3; N, 6.7. C,,H,,N,OP requires C, 76.76; H, 5.49; N, 6.63%);v,,,.(KBr) 1 330 (P=N), 1 600 (C=N), and 1 630 cm-" (C=O); G,(CDCl,) 2.70 (3 H, d, ,JPH1.6 Hz, Me) and 7.16-8.28 (20 H, m, Ph); G,(CDCl,) 22.6 (d, ,JPc 13.8 Hz, Me), 127.4-139.4 (Carom.),176.3 (d, ,JPc7.9 Hz, CO), and 183.5 (d, ,JPc 7.2 Hz, C=N); G,(CDCl,) 15.2; m/z 422 (M', 2%), 345 (20), 319 (51), and 201 (100). 1-Benzoyl-2,2-diphenyl-4-(p-tolyl)-1,3-diaza-2h5-phospha-penta-1,3-diene (6b), m.p. 184-185 "C (Found: C, 76.9; H, 5.8; N, 6.5. C,,H,,N,OP requires C, 77.05; H, 5.77; N, 6.42%); v,,,, 1 330 (P=N), 1600 (C=N), and 1630 cm-I (C=O);G,(CDCI,) 2.39 (3 H, s,p-Me), 2.75 (d, 4JpH1.6 Hz, Me), and 7.00-8.47 (19 H, m, ArH); G,(CDCl,) 21.3 (p-Me), 22.3 (d, ,JPc 13.8 Hz, Me), 127.4-143.3 (Carom.),176.0 (d,, Jpc 7.6 Hz, CO), 183.2 (d, ,JPc 7.2 Hz, C=N); Gp(CDC13) 15.2; m/z 436 (M', 373,359 (loo), and 333 (53).1-Benzoyl-4-(p-chlorophenyl)-2,2-diphenyl- 1,3-diaza-2h 5-phosphapenta-1,3-diene(6c). M.p. 183-184 "C (Found: C, 70.9; H, 4.75; N, 6.0. C,,H,,C1N20P requires C, 70.98; H, 4.85; N, 6.13%); vma,.(KBr)1 330 (P=N), 1 600 (C=N), and 1630 cm-' (Ca); GH(CDC1,) 2.69 (3 H, d, 4JpH1.7Hz, Me), and 7.34-8.30 (19 H, m, ArH); G,-(CDCl,) 22.4 (d, ,JPc13.6 Hz, Me), 127.6-138.9 (Carom.),176.3 (d, ,JPc 7.8 Hz, CO), 182.0 (d, ,JPc 7.0 Hz, C=N); Gp(CDC13) 16.0; m/z 457 (M+,273,355 (9), 353 (28), and 201 (loo).1-Ethoxycarbonyl-2,2-diphenyl-4-(p-tolyl)-1 ,3-diaza-2h5- phosphapenta-1,3-diene(7a). M.p. 125-126 "C (Found C, 71.4; H, 6.35; N, 7.05. C,,H2,N,02P requires C, 71.21; H, 6.23; N, 6.93%); vma,.(KBr)1280 (P=N), 1 600 (C=N), and 1620 cm-' (Ca); G,(CDCl,) 1.16 (3 H, t, 3JHH 7.9 HZ, Me), 2.41 (3 H, S,p-Me), 2.79 (3 H, d, ,JPH1.6 Hz, Me), 4.04 (2 H, q, CH,), and 7.08-8.12 (14 H, m, ArH); Gc(CDCl,) 13.6 (Me), 20.3 (p-Me), 21.5 (d, ,JPc 14.5 Hz, Me), 59.7 (d, ,JPc 1.6 Hz, OCH,), 127.0-142.5 (Carom.),160.4 (CO), and 182.4 (d, ,JPc 7.3 Hz, C=N); G,(CDCl,) 15.3; m/z 404 (M+,2%) and 359 (100). 1-Ethoxycarbonyl-2,2-diphenyl-4-(p-toly1)-1 ,3-diaza-2h'- phosphahexa-1,3-diene(7b).M.p. 117-1 18 "C (Found: C, 71.6; H, 6.4; N, 6.5. C,,H2,N,O2P requires C, 71.74; H, 6.51; N, 6.70%); v,,,,(KBr) 1280 (P=N), 1610 (C=N), and 1630 cm-' (C=O); 6,(CDCI,) 1.16 (6 H, t, 2Me), 2.43 (3 H, s, p-Me), 3.24 (2 H, dq, ,JHH6.3 Hz, 4JpH1.5 Hz, CH,), 4.0 (2 H, 9, OCH,), and 6.85---8.16(14H,m,ArH); G,(CDCl,) 11.4(Me), 13.5 (Me), 20.1 @-Me), 28.4 (d, ,JPc 12.6 Hz, CH,), 59.6 (d, 4Jpc1.5 Hz, OCH,), 126.9-142.2 (Carom.),160.3 (CO), and 187.5 (d, ,JPc 7.1 Hz, CN); Gp(CDC1,) 14.0; m/z 418 (M', 20%), 373 (74), 201 (5% and 153 (100). Hydrolysis of Compound (6a). Fragmentation Products.-A solution of compound (6a) (2.1 g, 5 mmol) in a mixture of dioxane (30 ml) and 2~ H2S04(30 ml) was heated 6 h at 50 "C. After aqueous work-up and extraction with methylene di- chloride, the organic phase afforded aminodiphenylphosphine oxide (0.9 g), m.p.190-191 "C (lit.,', 190-192 "C) and aceto- phenone (0.4 g). The remaining aqueous phase was treated with 3111 KOH until it became alkaline and was then extracted with CH,Cl,; evaporation of the extract led to benzamide (0.5 g), m.p. 128-129 "C. Synthesis of 1-Benzoyl-2,2-diphenyl-4-(p-toly1)-1,5-diaza-2L5-phosphapenta-1,3-diene @).-This compound was prepared by the same method as derivatives (2) with solutions of benzoyl azide (0.75 g, 5 mmol) in ether (10 ml) and (p-amino-p- tolylviny1)diphenylphosphine (1.6 g, 5 mmol) in ether (10 ml) and gave compound (8)(2.0 g, 92%), m.p. 162-163 OC (from hexane-methylene dichloride) (Found: C, 76.9; H, 5.6; N, 6.4.C,,H,,N,OP requires C, 77.05; H, 5.77; N, 6.42%); v,,,.(KBr) 1 360 (P=N), 1 650 (C=C-N), and 3 200 and 3 380 cm-' (NH,); 6,(CDC13) 2.35 (3 H, s,p-Me), 4.31 (1 H, d, 'JPH17.3 Hz, CH=), 6.67 (1 H, s, NH), and 7.04-8.39 (20 H, m, ArH + NH); 6,-(CDCl,) 20.6 @-Me), 73.0 (d, lJPc107.1 Hz, C-l), 126.2-140.3 (Carom.), 162.7 (C-2), and 176.6 (d, ,JPc6.3 Hz, CO);G,(CDCl,) 13.4; mjz 436 (M', 2279, 359 (43), 332 (52), and 185 (100). Synthesis of Diphenyl[2-(p-tolyl)-2-ureidovinyl]phosphine Oxide (ll).-To a suspension of KH (5 mmol) in THF (10 ml) was added dropwise, under argon, compound (9)9 or (5mmol) in THF (10 ml). The mixture was heated for 6 h at 60 "C and quenched with MeOH (20 ml) and water (20 ml). After extraction with methylene dichloride (100 ml), drying (Na,SO,) and evaporation of the extract gave crude compound(l1) (1.5 g, 8l%), m.p. 226-227 "C (from MeOH) (Found: C, 70.4; H, 5.7; N,7.3.C,,H,,N,O,P requires C, 70.20; H, 5.62; N,7.44%); vma,,(KBr) 1 180 (P=O), 1 600, 1 720 (C=O), and 3 200, 3 320, 3 400 cm-' (NH); 6,(CDC1,) 2.3 (3 H, s,p-Me), 5.14 (1 H,d, ,JPH 20 Hz, CH=), 5.4 (2 H, m, NH,), 7.05-7.80 (14 H, m,ArH), and 9.78 (1 H, s, NH); 6,(CDC13) 21.2 @-Me), 96.9 (d, lJPc104.0 Hz, =CHP), 126.7-139.3 (Carom.),155 (CO), and 158.1 (CHS); Gp(CDC13) 21.1; mjz 376 (M', 3%), 333 (85), 332 (90), and 77 (100). Synthesis of 3-(Diphenylphosphoramido)-3-(p-tolyl)acryl-arnide (13).-To a solution of compound (7a) (2.0 g, 5 mmol) in THF (20 ml) was added aluminium chloride (5 mmol) and the mixture was heated for 12 h at 80°C.After aqueous work-up and extraction with methylene dichloride, the extract was evaporated to give compound (13) (1.54 g, 82%), m.p. 182- 183 "C (from hexane-CH,Cl,) (Found: C, 70.0; H,5.5; N, 7.3. C,,H,,N,O,P requires C,70.20; H, 5.62; N, 7.44%); v,,,.(KBr) 1 220 (P=O), 1 630, 1 730 (C=O), 3 280, and 3 410 cm-' (NH); &H[(CD~),SO]2.2 (3 H, s,p-Me), 5.1 (1 H, d, 4Jp~2.0 Hz, CH=), 6.80-7.80 (10H, m, ArH + NH,), and 11.61 (1 H, d,,JPH12.5 Hz, NH); 6,[(CD,),SO] 21.0 (p-Me), 97.6 (d, ,JPc4.9 Hz, CH=), 126.7-138.0 (Carom.),154.9 (d, ,JPc 1.2 Hz, C), and 169.8 (CO); GP(CDCl3) 20.1; miz 376 (M', 30%), 333 (70), 332 (70), and 201 (100). Acknowledgements We thank the Comision Asesora de Investigacion Cientifica y Tecnica for the financial support and we are also indebted to the J.CHEM. 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