5823 Table I. Cyanosilylation ofp-Quinones (eq 2)'
7',yieldc
Ratio 2:3b
u-Ouinonea
l a (R1, Rz, R 3 = H ) l b (R1 = CH3; RP,R I = H) IC(R1 = OCH3; Rz, R3 = H)" Id (R1 = OCH3; Rz = H ; R3 CH3)' l e (R1, R z = OCH,; R3 = H)O If (Ri, R * = CH3; Ra = H) l g (R1. Rz = t-Bu; R B= H ) l h (Ri = H ; RZR3 = C4H4)i l i (R1 = C H 3 ; RZR3 = C4H4)j l j (R1 = O C H 3 ; RZRI = C4HJi
R4u (bp), "C
67-67,5 (100-102 (0.8mm)) 58-60 63.5-64 101.8-102
80 92 80 90 65 (100)
89:ll 1oo:o
1oo:o
1oo:o 94 :6 0:loo
. . .h
(100)
. . .h
(98) 75 96 82
91 :9h
1oo:o
(110-iio (0.1mm)) 72-73
~
Unless specified, the starting quinone is commercially available. b Ratios determined by nmr. c Yields in parentheses determined by n m r ; all others are of purified adduct. Values in parentheses are boiling point of liquid products. e C. de Corral, Ctiem. Abstr., 52, 72571' (1958). Reference IC. g Org. React., 4, 343 (1948). * Adduct reverts to quinone upon attempted distillation. Product always contaminated with 3-4% naphthoquinone. 7 Notation C a H 4refers t o fused benzene ring. 0
Table II. p-Quinols from TMSCN-Quinone Adducts (eq 3)' Protected auinone
2a (Rl, Rz, R 3 = H)
2~ (R1 z= OCHI; Rz, R3 = H) 2d (R1 = OCHI; Rz = H; R3 CHI) 2f (R1, Rz = CH3; Rs = H) 2h (R1 = H ; RzR3 = C4H4) 2j (R1 = O C H 3 ; R2R3 = C I H ~ ) a One equivalent of R M was added to 2 in ether a t -70". Reference 15b. Ctiem.,81, 1055(1950); seealsoref 15a.
CN
0 2
Me,SiO
-HO'
CN
'R 4
Mu, "C
89 86 75 65 73 87 77 89 79
76-78' 105-106.5d 48-50 48-50 102-104 114-115 37-43 103-104 125-126
F. Wessely and F. Sinwell, Moiiatsck. E. Adler, J. Dahlen, and G. Westin, Acta Cliem. Scatid., 14, 1580 (1960).
0
"HO' 'R 5
contrast to the behavior of unprotected p-quinones, organometallic reagents have been found to undergo clean 1,2 addition to 2 at -7O0l2 affording the adducts 4. These intermediates can then be deblocked to the desired p-quinols in high yield with silver fluoride in aqueous tetrahydrofuran (25'). Removal of the TMSC N blocking group under these conditions is virtually instantaneous. This general synthesis of p-quinols is far superior to existing methods.13 As illustrated in Table 11, the two-step conversion of the monoprotected quinones 2 into thep-quinols 5 proceeds in good yields.' With a simple synthesis of p-quinols now available, further utilization of these intermediates should be encouraged. For example, TMSCN-quinone adducts lc-e and l j may serve as useful precursors to substituted o-quinones. This is suggested by the fact that quinol 5j (R = CHI) may be transformed (Cu(BF&, CH3CN, 25") in 85 % yield to 7. l 4 On the other hand, p-quinols (12) Optimum yields of 4 are obtained with 1 equiv of RM in ether a t
- 70".
Z yield6 of 5
* Values correspond to purified quinol. e
tions on the unprotected quinone carbonyl, a wide variety of otherwise relatively inaccessible compounds can be synthesized in good yield. A simple demonstration of the utility of TMSCN-quinone adducts as effective precursors to p-quinols is illustrated (eq 3). In Me,SiO
RM" CH3Li CeHsMgBr n-C4HsLi n-C4H9MgBr CH3Li CH3Li CH3Li CH3Li CH3Li
At this temperature slightly better yields are obtained with the lithium as opposed to the magnesium alkyls, (13) For an excellent review of methods of preparation of p-quinols as well as their reactions see A . J. Waring, Aduan. Alicycl. Chem., 1, 129 (1966).
0
5i
0
7
such as Sa (R = CH3 or CsH5)15undergo facile dienonephenol rearrangement under standard conditions to substituted p-hydroquinones. Applications of this new quinone blocking procedure16 in the areas of alkaloid and quinone synthesis will be reported in the due course. Acknowledgment. We wish to thank the Camille and Henry Dreyfus Foundation for unrestricted research support. (14) Compound 7 has been synthesized independently: L. Fieser and C. Bradsher, J. Amer. Chem. SOC.,61, 417 (1939). This transformation correlates with the structural assignments for both 5j ( R = CHa) and 2j. (15) (a) S. Woodwin and B. Witkop, ibid., 79, 179 (1957); (b) Y . Abe, Bull. Chem. Soc. Jap., 18,93 (1943). (16) Detailed experimental procedures will be provided upon request. (17) Camille and Henry Dreyfus Teacher-Scholar Recipient (19711976); Alfred P. Sloan Fellow (1972-1974).
D. A. Evans,*" J. M. Hoffman, L. K. Truesdale Contribution No. 31 72 Department of Cliemistry, Uiiioersity of Califoriiia, Los Atigeles Los Aiigeles, California 90024 Receiaed hitie 18, 1973
Synthesis of a Tantalum Pentahydride Complex Sir: Phosphine-stabilized polyhydrides are known for transition metals of groups VI-VI11 but not for metals Communications to the Editor
5824
(toluene-&, ligand protons noise decoupled, 1 : 5 : 10: 10: 5 : 1 sextet, 22.4 ppm below 85 % H3P04). The hydride nmr spectrum, a 1 :4:6:4: 1 quintet (C6D6, T 10.70, ylphosphinoethane) is now reported. This synthesis extends to group V the series of third-row, formally JPH = 35.0 Hz), is consistent with stereochemical nondo, polyhydrides illustrated by H7Re(Ph2PCH2CH2- rigidity of the molecule over the accessible temperature PPh2)2and H6W(PMe2Ph)3. range (CHC1F2, t o - 140'). Compound 2 is fluxional Compound 1 was synthesized by two routes at 90', but rigid near OO.s All of the previously known niobium and tantalum K,Hz (1) TaC1; hydride complexes are derivatives of ( T - C ~ H ~ ) ~lo M . DMPE+ HaTa(DMPE)t The cyclopentadienyl ligands formally occupy six of (2) [TaPh6-14 A / DMPE the available coordination sites in these complexes by 1 T bonding" and in some cases further deactivate the metal by forming carbon t o metal Q bonds as in [(C,H5)In reaction 1, a mixture of 1.8 g (5.0 mmol) of TaCle, l 2 Comparison of the chemistry of the (C5H4)TaHI2. 3.8 g (25 mmol) of DMPE, and 2.0 g (51 mmol) of cyclopentadienyl derivatives with the potentially more potassium, in 10 ml of benzene, was agitated overnight reactive (DMPE)2TaH5is in progress. at 115" in a Hastelloy-C pressure vessel under 1500 psi of hydrogen. After filtration and evaporation of Acknowledgments. I thank P. Meakin for the nmr the solvent, the product was crystallized from hexane data, N. Schlichter for ir data, and U. Klabunde for t o yield 0.45 g of 1. The yields from this type of reacpermission to quote results prior to publication. tion have varied from 0 to 40%;. In reaction 2, a mixture of 54 g (0.058 mol) of [Li(THF)4][TaPh6](THF = (9) Spectra are analyzed as AA'BB'X systems. A detailed line shape analysis of the permutational process and X-ray diffraction tetrahydrofuran), 27 g (0.18 mol) of DMPE, and 250 studies of 2 are in progress. P. Meakin, L. J. Guggenberger, F. N. ml of T H F was agitated for 5 hr at 45" in a pressure Tebbe, and J. P. Jesson, to be submitted for publication. vessel under 1500 psi of hydrogen. Volatiles were re(10) M. L. H. Green, J. A. McCleverty, L. Pratt, and G. Wilkinson, J . Chem. Soc., 4854 (1961); E. K. Barefield, G. W. Parshall, and F. N. moved from the soluble portion of the reaction mixture Tebbe, J , Amer. Chem. Soc., 92, 5234 (1970); F. N. Tebbe and G. W. and the residue was crystallized from hexane to yield 7.6 Parshall, ibid., 93, 3793 (1971). (11) C. J. Ballhausen and J. P. Dahl, Acta Chem. Scand., 15, 1333 g of 1. An orange THF-insoluble solid, 4.9 g, present (1961). in the product mixture is presumably an anionic deriv(12) L. J. Guggenberger, Inorg. Chem., 12,294 (1973). ative of 1. Treatment of a benzene suspension of the Fred N. Tebbe solid with 1.2 ml of ethanol produced an additional 2.3 Contributiori No. 2020 from the Ceritral Research Department g of 1. Excess alcohol reduced the yield. Yields from Experimerital Statioit, E. I . du Porit de NemourA and Company reaction 2 are reproducible, 30-40 %. The pentahydride Wilmitigtori, Delaware 19898 is an air-sensitive white crystalline solid (mp 133-135" Received April 27, 1973 dec; mol wt calcd 486, found (cryoscopic in benzene) 464; ir (Nujol) 1544 cm-l (Ta-H stretch)). The hydride ligands in 1 are readily substituted. Exposure of the pentahydride to hydrogen chloride, Stereochemistry and Synthesis of the Antileukemic water, or ethanol results in rapid generation of hydroAgent Botr yodiplodin gen. Deuterium exchange at the hydride sites ( Y T ~ - D , Sir: 11 10 cm-l) occurs when the complex is heated in benzene-& solution at 80" under 900 psi of deuterium. In 1968, Arsenaultl defined the gross structure of an Like (C6Hj)2MH35 (M = Nb or Ta), 1 catalyzes the exantibiotic isolated from Botryodiplodia theobromae change of hydrogen with benzene.6 At 80" in benzene Pat. as 2-hydroxy-3-methyl-4-acetyltetrahydrofuran solution under 1500 psi of carbon monoxide, it is con(I) by chemical ionization mass spectrometry. Aside verted to the hydridotantalum carbonyl HTa(C0)2from its antibiotic character, compound I (botryo(DMPE)? (2) in 58% yield.7 (Orange crystals from diplodin) also exhibits antileukemia activity and the hexane; mp 140-141"; mol wt calcd 538, found 538 interesting property of turning the skin of individuals (mass spectrum); ir (C6D6solution) 1737 (C=O stretch) various shades of pink22-3 hr after its application. and 1589 cm-' (Ta--H stretch)). The corresponding deuteride (VT&-D = 1137 cm-l), ca. 40% enriched, was obtained by a similar procedure from (H,D)jTa(DMPE)2. The compositions and molecular dynamics of 1 and 2 are verified by nmr data.8 For 1, the hydride count is obtained from the multiplicity of the 31P spectrum of groups IV and V.'
The synthesis of H5Ta(DMPE)2
(1) (DMPE = (CH,)2PCH2CHzP(CH3)z,1,Zbisdimeth-
(1) A recent review is "Transition Metal Hydrides," Vol. 1, E. L. Muetterties, Ed., Marcel Dekker, New York, N. Y., 1971. (2) J. Chatt and R. S. Coffey, J . Chem. Soc. A , 1963 (1969). (3) J. R. Moss and B. L. Shaw, Chem. Commun., 632 (1968). (4) The synthesis of this new anion by U. Klabunde will be reported separately. (5) U. Klabunde and G. W. Parshall, J. Amer. Chem. Soc., 94, 9081 (1972). (6) U. Klabunde, unpublished results. (7) Compound 2 has been independently synthesized in the laboratory of J. A . Connor. J. A. Connor, personal communication. (8) Microanalytical data are: Calcd for Cl~HarPaTa(1): C, 29.6; H, 7.7; P, 25.5; Ta, 37.2. Found: C, 29.8; H, 7.8; P, 25.5; Ta, 37.5. Calcd for CidHaaO~PaTa (2): C, 31.2; H, 6.2. Found: C, 31.2; H, 6.1.
Journal of the American Chemical Society
95:17
I
I1
Although the nmr of I in CC14was complicated, due to anomers at Cz, the corresponding acetate I1 appeared to be a single isomer and was tentatively assigned structure 11,' based on the value of J H ~ , H(7, Hz). Because of the ambiguity of assigning stereochemistry (1) G. P. Arsenault, J. R. Althaus, and P. V. Divekar, Chem. Commun., 1414(1969). (2) R. Sen Gupta, R. R. Chandran, and P. V. Divekar, Indian J. Exp. BioI.,4,152(1966). (3) Results of preliminary testing by the National Institutes of Health.
/ August 22, 1973
