摘要:

(R2N)2P CH2 P(NR2)2 (CF3)2CO a R = Me b R = Et CH (R2N)2P (CF3)2HCO P(NR2)2 1a,b 2a,b (CF3)2CO (R2N)2P CH P(NR2)2 + Cl – HCl 4a,b 3a,b (R2N)2P C P(NR2)2 HC(CF3)2 O (CF3)2CH O HC(CF3)2 O (CF3)2CH O An unusual reaction of hexafluoroacetone with methylenediphosphines. Facile synthesis of carbodiphosphoranes Igor Shevchenko† Institute of Bioorganic Chemistry Murmanskaya Street 1 252660 Kiev Ukraine The oxidation of bis[bis(dialkylamino)phosphinyl]methanes with hexafluoroacetone does not lead to the expected dioxaphospholane heterocycles but yields quantitatively carbodiphosphoranes. It is well known that phosphines react with 2 equiv. of hexafluoroacetone (HFA) to give phosphoranes in which the phosphorus atom is part of a dioxaphospholane heterocycle.1–4 It turns out that this is not the only possible pathway for this reaction.Here we report on an unusual reaction of HFA with bis[bis(dialkylamino)phosphinyl]methanes 1a,b which gives quantitatively carbodiphosphoranes 3a,b (Scheme 1). Formally this reaction can be considered to be an addition of the tautomeric P–H ylide form of 1 to the carbonyl function of HFA. The presence of a methylene group between the two phosphorus atoms is thus a necessary condition for this reaction. After slow bubbling of gaseous HFA through a solution of 1a or 1b in hexane at 20 °C NMR spectra of the reaction mixtures show the presence of only compound 3a or 3b respectively; the 31P NMR spectra of the reaction mixtures display one singlet at d 33–37. Carbodiphosphorane 3a is stable in hexane solution at room temperature for several hours whereas 3b containing the more bulky diethylamino substituents is respectively more stable and its hexane solution can be stored without decomposition for two days.Evaporation of the solvent causes decomposition of the molecule. The choice of hexane as a solvent is very important for this reaction. In other solvents carbodiphosphoranes 3a,b are less stable and their synthesis may be accompanied by the formation of byproducts. The 1H NMR spectra of 3a and 3b were recorded immediately after HFA had been added to a solution of 1a or 1b in [2H8]toluene.‡ They show a characteristic low field septet at d 6.2 confirming the location of the two equivalent protons a to the CF3 groups. It is interesting that the dimethylamino groups of 3a appear in the 1H NMR spectrum not as a doublet but as a pseudo-triplet at d 2.59 with a broadened central line which is consistent with the NMR data of known compounds.The analogous carbodiphosphorane having chlorine atoms instead of HFA units at the two phosphorus atoms shows the same pattern for the Me2N groups in its 1H NMR spectrum.5 The mechanism of this reaction probably includes the intermediate formation of monoylides 2a or 2b. However we could not detect these compounds via NMR spectroscopy. Even if only 1 equiv. of HFA was added to the methylenediphosphines 1a,b the 31P NMR spectrum of the reaction mixture displayed only two equal signals for the starting compound 1 and the reaction product 3. The ylidic structure of carbodiphosphoranes 3a,b is confirmed by their reaction with HCl which gives the stable salts 4a,b. As a strong base 3a,b reacts with ammonium hydrochlorides.That is why 4a,b can also be formed in small quantities together with 3a,b if starting methylenediphosphines 1a,b are contaminated with dialkylammonium chlorides. However 4a,b are not soluble in hexane and can be easily separated. The structures of 4a,b are entirely consistent with the NMR data obtained.§ In contrast to most carbodiphosphoranes described previously,6–10 compounds 3a,b are easily obtainable and can be used in further reactions without isolation from the reaction mixture. The possible application of 3a,b in Wittig reactions and the presence of hydrogen atoms a to the CF3 groups make these compounds interesting synthons for organic and elementoorganic synthesis. We are currently investigating their chemical properties.Dedicated to Doctor Hans-Martin Schiebel on the occasion of his 65th birthday. Notes and References † E-mail ishev@bioorg.kiev.ua ‡ Selected data for 3a dP(80 MHz C6H14) 36.7; dH(200 MHz [2H8]toluene) 2.59 (pseudo t 3JPH 11.6 24 H NCH3) 6.25 (sept 3JFH 6.8 2 H CHCF3); dF(188.3 MHz C6H14) 273.0 (d 3JHF 6.8 12F). For 3b dP(80 MHz C6H14) 33.6; dH(200 MHz [2H8]toluene) 0.98 (t 3JHH 7.1 24 H NCH2CH3) 3.00 (m 16 H NCH2CH3) 6.09 (sept 3JFH 6.8 2 H CHCF3); dF(188.3 MHz C6H14) 272.9 (d 3JHF 6.8 12F). § To a solution of 3a or 3b in hexane 1 equiv. of HCl in Et2O was added at 20 °C. The precipitated 4a or 4b was separated and recrystallized from CH2Cl2–Et2O at 215 °C. Selected data for 4a 63% mp 183–185 °C (decomp.); dP(80 MHz CDCl3) 58.6; dH(200 MHz CDCl3) 2.71 (pseudo t 3JPH 10.7 24 H NCH3) 3.67 (t 2JPH 10.0 1 H PCHP) 6.71 (sept 3JFH 5.9 2 H CHCF3); dC(50.3 MHz CDCl3) 7.4 (t 1JPC 209 PCP) 37.3 (pseudo t 2JPC 4.9 8C NCH3) 70.3 (sept 2JFC 34 2 C CHCF3) 120.8 (q 1JFC 285 4CF3); dF(188.3 MHz CDCl3) 273.9 (d 3JHF 5.9 12F).(Calc. for C15H27ClF12N4O2P2 C 29.02; H 4.38. Found C 28.77; H 4.32%). For 4b 52% mp 151–153 °C; dP(80 MHz CDCl3) 59.1; dH(200 MHz CDCl3) 1.06 (t 3JHH 6.8 24 H,NCH2CH3) 3.05 (m 16 H NCH2CH3) 3.23 (t 2JPH 13.7 1 H PCHP) 6.75 (sept 3JFH 5.9 2 H CHCF3); dC(50.3 MHz CDCl3) 7.3 (t 1JPC 209 PCP) 13.7 (s 8C NCH2CH3) 40.6 (s 8C NCH2CH3) 70.4 (spet 2JFC 34 2C CHCF3) 120.8 (q 1JFC 285 4CF3); dF(188.3 MHz CDCl3) 273.0 (d 3JHF 5.9 12F) (Calc. for C23H43ClF12N4O2P2 C 37.69; H 5.91. Found C 37.12; H 5.79%). 1 M. Witt K. S. Dathathreyan and H. W. Roesky Adv. Inorg. Chem.Radiochem. 1986 30 223. 2 R. Burgada and R. Setton ‘Preparation Properties and Reactions of Phosphoranes’ in The Chemistry of Organophosphorus Compounds ed. F. R. Hartley in The Chemistry of Functional Groups Series ed. S. Patai Wiley Chichester New York Brisbane Toronto Singapore 1994 vol. 3 ch. 3 pp. 185–272. 3 F. U. Seifert and G.-V. R�oschenthaler J. Fluorine Chem. 1995 70 171. 4 I. Neda C. Melnicky A. Vollbrecht A. Fischer P. G. Jones and R. Schmutzler Z. Anorg. Allg. Chem. 1996 622 1047. Scheme 1 Chem. Commun. 1998 1203 5 A. P. Marchenko G. N. Koydan N. A. Oleynik I. S. Zal’tsman and A. M. Pinchuk Zh. Obshch. Khim. 1988 58 1665. 6 A. W. Johnson Ylides and Imines of Phosphorus Wiley New York Chichester Brisbane Toronto Singapore 1993 ch. 3 pp. 64–68. 7 O. I. Kolodiazhniy The Chemistry of Phosphorus Ylids N. Dumka Kiev 1994 ch. 5 pp. 330–338. 8 P. Dyer O. Guerret F. Dahan A. Baceiredo and G. Bertrand J. Chem. Soc. Chem. Commun. 1995 22 2339. 9 H. Schmidbaur and S. Schnatterer Chem. Ber. 1983 116 1947. 10 R. Appel U. Baumeister and F. Knoch Chem. Ber. 1983 116 2275. Received in Liverpool UK 5th March 1998; 8/01805G 1204 Chem. Commun. 19

ISSN:1359-7345    

DOI:10.1039/a801805g

出版商:RSC    

年代:1998

数据来源: RSC