J . Am. Chem. SOC.1985, 107, 5849-5855 h 30 min). Removal of the solvent and washing with methanol provided the endoperoxide of the tetraester (31 mg, 71%) as white crystals. A solution of this compound (31 mg) in warm dioxane (1 mL) was mixed with 1 M KOH in methanol (5 mL) and refluxed for 30 min. The precipitate was collected and washed with methanol (2 mL) leading to the endoperoxide of the tetrapotassium salt, DPATCO, (30 mg, 83%). Endoperoxide of Disodium 3,3'-( 1,4-Naphthylidene)dipropionate(NDPO2). Sensitox I1 (100 mg) was added to a solution of NDP (1 g) in water (0.5 mL) and methanol (9.5 mL). This mixture was irradiated for 3 h at 5 OC under stirring, with a 500-W mercury high-pressure lamp (Philips S P 500) using a filter (GG 515, Schott) and maintaining a continuous bubbling of oxygen. The sensitizer was filtered off and washed with chilled methanol (20 mL, 0 "C). The resulting solution was dried by stirring at 0 "C with Na2S04 (2 g) during 15 min. After filtration, cold ether (60 mL, 0 "C) was added to the solution and stirred 10 min to induce precipitation of the endoperoxide NDPO,. The precipitate was collected and dried 2 h in vacuo (0.1 torr, 0 "C) yielding NDPO, (850 mg, 80%) as a white powder. HPLC analysis showed 95% of NDPO,, 4% starting material, and about 1% of secondary products. Solid NDPO, is quite stable at -20 OC. Instrumention. Analyses of the reaction products were carried out by HPLC (Varian 8500, column lichrosorb RP 18) using a mixture of H20/C2H50H/H,P04as eluent (280/320/1 for RTC, 330/270/1 for DPATC and NDP, l50/450/0 for a-terpinene), and UV detection (260 nm for RTC, 233 nm for DPATC, 210 nm for NDP and a-terpinene) was performed with a variable-wavelength monitor (Spectromonitor 111, Sopares). The IR spectrum of ascaridol was recorded on a Perkin-Elmer 297 spectrophotometer. The nuclear magnetic resonance spectrum ('H NMR) of ascaridol was obtained on a Varian EM 390 spectrometer. Screening of the Periodic Classification. A mixture of 1 mL of H 2 0 , 100 pmol of NaOH (lo-' M), 100 +mol of H 2 0 2(IO-' M), and 0.2 pmol (2 X lo-, M) of RTC was stirred in the dark, at room temperature for 24 h with 20 pmol (2 X lo-, M) of the mineral compound under study. The disappearance of RTC and appearance of RTCO, were monitored by HPLC after 1 h and 24 h. Formation a ThermodissociableEndoperoxide. A mixture of 1 mL of H 2 0 , 100 pmol of NaOH (lo-' M), 1 mmol of H 2 0 2(1 M), and 5 pmol (5 X lo-, M) of NDP was stirred at room temperature with the mineral compound under study (mineral compound/concentration/reaction time: CIO-/1.5 X lo-' M/5 min, Nd20,/5 X lo-' M/3 h, MoO,~-/IO-~M/3 h, Ca(OH),/5 X lo-' M / I h). The disappearance of NDP and appearance of NDPO, were monitored by HPLC. At the end of the reaction, the mixture was centrifuged and the liquid was warmed 1 h at 50 "C to regenerate NDP from NDP02. Deuterium Solvent Effect. A solution of 10 pL of DPATC lo-, M in D 2 0 (2 X M), 25 p L of NaOH 2 M in D 2 0 (IO-' M), 2.5 pL (Mood2-),or 5 pL (CIO-, Nd,O,, Ca(OH),) of H20, 30% in H 2 0 (5 X IO-, M or lo-' M) was mixed with H 2 0or D,O in order to obtain a final volume of 500 pL. Then I O pmol(2 X IO-, M) of the mineral compound was added with stirring. The disappearance of DPATC and appearance of DPATC02 were monitored by HPLC after 15 h.
5849
Peroxidation of a-Terpinene. Analytical Scale. A mixture of 0.75 mL of H 2 0 (30%), 1.75 mL of CH30H (70%), 250 pmol of NaOH (lo-' M, except for Ca(OH)2),500 pmol of H 2 0 2(2 X IO-' M), and 25 pmol of a-terpinene (lo-, M) was stirred at room temperature with the mineral compound under study (mineral compound/concentration/reaction time: C10-/7 X IO-, M / I h, Nd20,/5 X M / 7 h, Na,M00,/10-~ M/30 min, Ca(OH),/5 X IO-, M/7 h). Under these conditions, HPLC analysis showed that most of the a-terpinene had disappeared and that the corresponding endoperoxide (ascaridol) was produced in addition to secondary products. Preparative Scale. A mixture of 8 mmol of H,O, (2 X lo-' M), 4 mmol of NaOH (IO-] M), 0.4 mmol of Na2Mo04(IO-, M), and 0.8 mmol of a-terpinene (1 I O mg, 2 X IO-, M) was introduced into 40 mL of a mixed solvent, C H 3 0 H / H 2 0 ,70:30. The composition of the redbrown homogeneous solution was monitored by HPLC. After 30 min at room temperature the solution had faded to a light yellow color, a-terpinene had completely disappeared, and a product with the same retention time as ascaridol had emerged. Water (50 mL) was added and the mixture was extracted with ether (4 X 50 mL). The ethereal layer was washed with water (20 mL) and dried with MgSO,. Evaporation yielded an oil (70 mg) which showed the same IH NMR and IR spectra as an authentic sample of ascaridol prepared by photooxygenation.
Note Added in Proof. A recent paper of Evans agrees with our finding of IO2 generation in the reaction H 2 0 2 I04-.43
+
Registry No. RTC, 78034-60-3; RTCO,, 78075-92-0; DPATC, 83687-18-7; DPATCO,, 97826-16-9; NDP, 97860-58-7; NDP02, 97860-59-8; Sensitox 11, 94035-43-5; O,, 7782-44-7; H,O,, 7722-84-1; CaO, 1305-78-8; SrO, 1314-11-0; BaO, 1304-28-5;CIO-, 14380-61-1; BrO-, 14380-62-2; Au3+, 16065-91-1; IO3-, 15454-31-6; IO4-, 1505635-6; Nd20,, 1313-97-9; MOO:-, 14259-85-9; Ca(OH),, 1305-62-0; D,O, 7789-20-0; Sc,O,, 12060-08-1; La,O,, 1312-81-8; H,TiO,, 12026-28-7; ZrO(N03)2, 13826-66-9; NaVO,, 137 18-26-8; Na2W04, 13472-45-2; Na2Mo0,, 7631-95-0; Pr,O,,, 12037-29-5; Sm203,1206058-1; Eu203,1308-96-9; Dy,O,, 1308-87-8: Er203, 1314-37-0; Yb203, 12061-16-4; Tho,, 1314-20-1; NaC10, 7681-52-9; NaBrO, 13824-96-9; Tb40,, 12037-01-3; Ho203,12055-62-8; Lu203. 12032-20-1; %(OH),, 18480-07-4; Ba(OH),, 17194-00-2; Y,03, 1314-36-9; ZrO,, 1314-23-4; HfO,, 12055-23-1; Ta205, 1314-61-0; K2Cr0,, 7789-00-6; AuCI,, 13453-07-1; CeO,, 1306-38-3; Gd2O3, 12064-62-9;(NH,),U20,, 778322-4; KI03, 7758-05-6; NaIO,, 7790-28-5; Tm,O,, 12036-44-1; Nb20S. 1313-96-8; ZnO, I3 14-13-2; Cd(OH)2,21041-95-2; Ga20,, 12024-21-4; IrCI,, 10025-97-5; GeO,, 1310-53-8; Bi,O,, 1304-76-3; K2Te04,1557191-2; a-terpinene, 99-86-5; ascaridol, 512-85-6; methanol, 67-56-1; hematoporphyrin, 14459-29-1; 9,10-diphenyl-2,3,6,7-tetra(methoxycarbony1)anthracene endoperoxide, 97860-60- 1,
(43) Evans, D. F.; Upton, M. W. J . Chem. SOC.,Dalton Trans. 1985, 1141-1 145.
A Theoretical Study of Model Substituted Phosphoranes, PH4X: Apicophilicities, Geometries, and Electron Densities Robert S. McDowellt and Andrew Streitwieser, Jr.* Contribution from the Department of Chemistry, Uniuersity of California, Berkeley, California 94720. Receioed September 4, 1984
Abstract: The relative energies of model apically and equatorially substituted phosphoranes, PH4X, are calculated for both standard and fully optimized structures. The resulting order of ligand apicophilicity is C1 > C N > F > C C H > H > CH, > OH > 0- > S- > NH2 > BH,. Apicophilicity is enhanced by ligand electronegativity and diminished by 7c donation; the effects of these u and s interactions on the remaining PH4 moiety and the concomitant geometrical changes resulting from incorporation of the substituent into the phosphorane system are examined using electron density analysis. We conclude from this analysis that d-functions on phosphorus are important in bonding to the apical ligands.
Displacement reactions of tetracoordinate phosphorus, including phosphate ester hydrolysis and the Wittig reaction, proceed by 0002-7863/85/1507-5849$01.50/0
means of metastable trigonal-bipyramidal intermediates, with the attacking and leaving groups occupying apical positions.' N u 0 1985 American Chemical Society
5850 J . Am. Chem. Suc.. Vol. 107. Nu. 21, 1985 cleophiles are thought to attack along the tetrahedral face of the reactant system;2 if the intermediate thus formed has an apical leaving group, the reaction proceeds with stereochemical inversion at phosphorus, in a manner akin to the SN2reaction.) If the initial intermediate has the leaving group occupying an equatorial site, permutational isomerization of the ligands is required in order to achieve the desired apical orientation. Here. the stereochemical result of the reaction depends on whether the number of isomerizations is even (inversion) or odd (retention)?.3L As such, because pentacoordinated phosphorus represents a bona fide intermediate state (rather than a transition state) in the reactions of tetracoordinated phosphorus.lF-8 a thorough analysis of the bonding mechanisms of pentamrdinated phosphorus is requisite for any understanding of these reactions. Because a number of stable cyclic5 and acyclic6 phosphoranes are known, certain generalizations can be made regarding pentaccardinated phosphorus.' Excluding some bicyclic systems in which ring strain and steric factors determine ligand topology: virtually all phosphoranes exist as trigonal bipyramids.5f-q Intramolecular ligand site exchange is assumed to proceed either by Ugi's turnstile mechanismlo or by a pseudorotation scheme ( I ) ( 8 ) Fenton, G. W.; Ingold. C. K. J. Chem. Soe. 1929, 2342. (b) Fenton. G.W.; Hey, L.; Ingold. C. K. Ibid. 1933. 989. (e) Kumli, K. F.; McEwen, W. E.; Van der Werf, C. A. J. Am. Chem. Sw.1959.81.3805, (d) Blade-Font, A,; Van der Werf, C. A,; McEwen. W. E. Ibid. 1960.82.2646, (e) Parisek, C.B.; McEwen. W. E.; Van der Werf, C . A. Ibid. 1960.82.5503, (0 McEwen. W. E.; Blade-Font. A,; Van der Werf. C. A. Ibid. 1962.84. 677. (9) McEwen. W. E.; Kumli. K. F.; Blade-Font, A,; anger. M.; Van der Werf, C. A. Ihid. 1964. 86, 2378. (2) (a) Gillespie. P.; Ramirer. F.; Ugi, 1.; Marquarding. D. Angew. Chem., Inr. Ed. Engi. 1973, 12. 91. (b) Gillcrpie. P.; Hoffmann, P.; Klusaeek, H.; Marquarding, D.;Pfohl. S.; Ramirez. F.:Tsulis. E. A,; Ugi. 1. Ibid. 1971, IO,
687. (3) (a) Ugi, 1.; Ramirw. F. Chem. Br. 1972.8, 198. (b) Hall, C. R.: Inch. T. D. Terrahedron 1980.36.2059. (4)Axial attack involves reaction at the face of a tetrahedron and is so commonly accepted that Trippet (ref 18) simply assumed such reaction. Equatorial reaction involves attack at the edge of the tetrahedron. Nevertheless. Minot (Minot. C. Nouo. J. Chim. 1981. 5, 319-325) has recently proposed a retention mechanism involving such an quatorial attack by a nuclmphile with axial expulsion of the leaving group. I t d a s not seem to have been recognized that for the identity ease, where entering and leaving nu-
cleophile are the same. such a praeess violates the Principle of Microscopic Reversibility since the mechanisms for forward and back reactions are now different. Since identity reactions have no real uniqueness among general nucleophiles, this mechanism is not probable for the general case. ( 5 ) (a) Ramirez, F. Ace. Chem. Ret. 1969,I, 168. (b) Ramirer. F. Bull. Soc. Chim. Fr. 1970,3491. ( c ) Hamilton, W. C.; La Plaea, S. J.; Ramirez, F.; Smith, C. P. J. Am. Chem. Soc. 1967, 89. 2268. (d) Swank. D. D.; F. Ibid. 1971,93, 5236. (e) Hague, Caughlan. C. N.: Ramirer. F.; Pilot, I. M. U.; Caughlan, C. N.; Ramirer, F.; Pilot, J. F.; Smith, C. P. Ibid. 1971, 93. 5229.
to) (a1 l l l n w n . K W ; Bancll. L S lnorg Chew 1965. 4, 1775. (b) Rarlcll. L S.. I h n r c n . K H' Ib,d 1965.4 , 1777 (c) You. H.: Bartcll. L S J Mol. Srrucr 1973. IS. 209 Id) Shcldrick. W S A m Cr)rrallopr 1975. R J I . 1770 ( < I Obrrhnmmcr. H , SchmutAcr. R J Chcm. Z , c . Dalton Tronr 1976. 1154 ( 0 Picrce. S B.. Cornwall. C D J . Chem. Phw 1968. 48,21 18. (g) Adamb,'W. 1.;Bartell. L. S. J. ,&I. Strucr. 1971, 23. (hi Oberhammer, H.; Grabe, J. 2.NarurJorseh. 1975,308, 506. (i) Ohlberg,
6
S.M. J. Am. Chem.Soe. 1959,81.811. (i) Bryan, R. F. Ibid. 1964,86,733. (k) Gundcrson. G . ;Hedberg. K. J. Chem. Phys. 1969,51.2500. (I) Talles, W. M.;Gwinn. W.G. Ibid. 1962.36, 1119. (m) Kimura, K.;B2uer.S. H. Ibid. 1963.39.3172, (n) Clippard, F. B.. Jr.;Bartell.L.S. lmrg. Chem. 1970, 4, 805. ( 0 ) Brown, D. S.;Einstein. F. W. B.;Tuuck. D. G.Ibid. 1969.8. 14. ( 0 ) Beauchamo. A. L.: Bennett. M. J.:Cotton. F. A. 3. Am. C h o n S m . 190, 6675. (&Joy, G.; Gaughan, A. P., Jr.; Wharf, 1.; Shriver, D. F.: Dougherty, J. P. Inorg. Chem. 1975, 14, 1795. (7) For a Summary of experimental and theoretical work on pentacaordinated phosphorus systems, see: Holmes. R. R. 'Penlacoordinated Phosphorus": American Chemical Saeietv: Washineton. D.C.. 1980: Vol. I and 11, ACS Monographs No. 175 and 176 and refer&& mntained therein. (8) (a) Holmes. R. R.; Dieters. J. A. J. Am. Chem. Soe. 1977.99.3318. (b) Howard. J. A,; Ruuell, D. R.; Trippelt, S. J. Chem. Soe.. Chem. Commun. ~
~~
~
~
~
~
.,,". ",". (9) (a) Westheimcr. F. Ace. Chcm. Res. 1968. I, 70. (b) Muetterlicr. E.
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