Organometallics 1986, 5 , 256-262
256
Synthesis of O - C I C ~ H , C H ~ C ~ ~ C ~ H , F ~(7d) C ~from +PF~7a. The reaction of ethyl acetoacetate with 7a according to the general procedure gave a 65-70% yield of 7d as yellow crystalline product after recrystallization from methylene chloride-ether: 'H NMR (CD3COCD3)6 6.88 (d, 1 H), 6.59-6.68 (m, 2 H), 6.46-6.52 (m, 1 H, aromatic), 5.23 (s, 5 H, Cp), 4.14, 4.23, 4.32, 4.41 (AB, 2 H, CH2, JAB 18 Hz), 4.19, (q,2 H, CH2, J 7 Hz), 1.24, (t, 3 H, OCH2CH3,J i= 7 Hz); N M R (CD&OCD,) 6 169.03 (CO),109.01,99.63,90.37,89.75,88.77,88.31 (complexed aromatic), 80.31 (Cp),62.17 (CH,), 38.83 (OCH,), 14.35 (OCH,CHJ; IR (cm-', KBr) 1745 (CO); mp 138-140 "C. Anal. Calcd for C15H16C102FePF&C, 38.77; H, 3.47; c1, 7.64. Found: C, 38.56; H, 3.56; C1, 7.59. Decomplexation Reactions. A 1-mmol sample of each complex (3,7c, 2c) was placed in a vacuum sublimator, dissolved in a minimum amount of methylene chloride, and dried to a thin film using a Nz stream. The sample was heated by using an oil bath under vacuum (0.25 mm). After 2 h of heating at 200 "C, the material from the cold finger was removed by dissolution with chloroform. After removal of chloroform, the white residue was washed with hexane (2 X 5 mL) to remove the ferrocene formed during this process. The white solid can be redissolved in the
-
minimum amount of ether and recrystallized with hexane. Specifically, for the vacuum sublimation of 462 mg of 3, the yield of deoxybenzoin was 178mg (91%),mp 54-56 "C (lit.%55-56 "C). Similarly from 496 mg of 7c, the yield a-(0-chloropheny1)acetophenonewas 211 mg (92%): mp 67-69 "C; 'H NMR (CD3COCD3)6 8.05-8.2 (m, 3 H), 7.3-7.7 (m,6 H, aromatic), 4.53 (s, 2 H, CH,); IR (cm-', KBr) 1700 (CO). Anal. Calcd for Cl4Hl1ClO: C, 72.87; H, 4.80. Found C, 72.55; H, 4.80. From 1 mmol of 2c, the yield of 5,5-dimethyl-2-phenylcyclohexane-1,3-dione was 53%: mp 192 "C (lit.27192-193 "C); 'H NMR (CDC13)6 7.1-7.6 (m, 5 H, aromatic), 6.45 (b s, 1 H, OH), 2.4 (s, 4 H, CHZ), 1.2 (s, 6 H, CH3).
Acknowledgment. We thank t h e Office of Naval Research for support of this work under Contract N0001483K-0306. (26) Truce, W. E.; Abraham, D. J. J. Org. Chem. 1963, 28,964. (27) Neilands, 0.; Vanags, G.; Gudriniece, E. J . Gen. Chem. USSR (Engl. Transl.) 1958, 28, 1201; Chem. Abstr. 1958, 52, 19988. Also: Beringer, F. M.; Forgione, P. S.; Yudis, M. D. Tetrahedron 1960,8,49.
Intra- and Intermolecular Rearrangements in Fp($-allyl) and Fp( q2-olefin) Complexes J. Celebuski, G. Munro, and M. Rosenblum" Department of Chemistry, Brandeis University, Waltham, Massachusetts 02254 Received May 13, 1985
(v1-l-Bromoallyl)Fp 6 and (+l-brom0-2-methallyl)Fp 9 [Fp = C,H,Fe(CO),] undergo substitution reactions by aryl-, vinyl-, and 2-methylcyclohexanone enolate zinc chloride to give rearranged condensation products 7a-d and loa-c. Deuterium labeling studies have shown that these products can be accounted for in terms of a slow, rate-limiting rearrangement through a [1,3] sigmatropic shift of the F p group. The resulting allylic bromide then undergoes rapid coupling by SN2'displacement of bromide. Deuteration of (7'-cis-1-bromoally1)Fp with deuteriotriflic acid proceeds stereospecifically trans to the Fp-carbon a-bond to give a single diastereomeric product 5-d. On standing, this cation undergoes stereospecific rearrangement 5-d' in equilibrium with 5-d. A mechanism involving concerted to (~1-trans-l-deuterio-3-bromoallyl)Fp intramolecular 1,3-migration of both F p and Br groups has been proposed for this reaction. A similar transposition of these groups has been observed in the bromination of ethyl trans-4-Fp-crotonate (15).
Introduction While [1,3] sigmatropic shifts are well-known for a number of a-allyl derivatives of the main-group metals,'S2 such behavior is less well documented for t h e corresponding transition-metal complexes. We recently provided evidence that the facile rearrangements observed in (7l-allyl)Fp complexes [ F p = C5H5Fe(C0)2]pr~ceed by a radical chain SH2'mechanism in which the chain-carrying species is the relatively stable 17-electron Fp. radical (eq
Fp,
1).2
Fp-
F
p
Scheme I 2Fp.
T
+
Fp'.
Fp'.
-
F
+
CO
p
'
R
T
+
Fp*
R
40. R=H b. R=Me
+
Fp'.
Fp'
+
Fpa
4c
Nondegenerate [1,3] sigmatropic rearrangements of ( ~ ~ - a l l y l ) complexes Fp have generally been observed to give (1)Mann, B. E. In "Comprehensive Organometallic Chemistry"; Wilkinsonn, G., Ed.; Pergamon Press: Oxford, 1982; Vol. 3, Chapter 20. (2) Rosenblum, M.; Waterman, P. J. Organomet. Chem. 1981, 206, 197.
0276-7333/86/2305-0256$01.50/0
preferentially the product with the least substituted Fe-C bond, as would be expected for t h e relatively electropositive Fp r a d i ~ a l . This ~ is illustrated by the formation of the 1-butenyl complex 3 on deprotonation of either the cisor trans-2-butene complex l.4 T h e initially formed (3) Symon, D.A.;Waddington, T. C. J. Chem. SOC.,Dalton Trans. 1975, 2140. Green, J. C. Struct. Bonding (Berlin) 1981,43,37. (4) Cutler, A.; Ehentholt, D.; Giering, W. P.; Lennon, P.; Raghu, S.; Rosan, A,; Rosenblum, M.; Tancrede, J.; Wells, D. J. Am. Chem. SOC. 1976, 98, 3495.
0 1986 American Chemical Society
Organometallics, Vol. 5, No. 2, 1986 257
Fp(q'-allyl) and Fp(q2-olefin) Complexes
methallyl complex 2 is not observed in these reactions since at room temperature its rearrangement is more rapid than its formation. r
Table I substr
nucleophile
product
yield, %
93
7
24
2
1
Similarly, the replacement of Fp by Fp' (Fp' = C,HJ?e(CO)L) in 4a,b may readily be achieved by a radical chain process., However, this reaction fails for the terminally substituted allyl complex 4 (Scheme I). The above generalization appears to be a useful guide to the preferred structure and to the reactions of alkylsubstituted (?'-allyl)Fp complexes, but some more recent observations with functionalized (7'-ally1)Fp complexes now illustrate its limitations, with respect to the prediction of reaction products derived from such potentially tautomeric systems. Furthermore, we observed a new stereospecific rearrangement in Fp(q2-bromoolefin) cations, which further illustrates the high mobility of the Fp group. These observations were made in the course of studies designed to extend the methods for elaborating the ligand in (q'-allyl)Fp complexes and form the substance of this paper.
73
100
MeZnCl
75
mznc'
61
24
Results and Discussion The most commonly employed means for elaborating simple (1'-ally1)Fp complexes has been through electrophilic addition to these substances, followed by deprotonation of the resulting cationic olefin complex (eq 2).'
+
FP-
E+
-
F
p
+
L E
EtSN FpE(2)
We sought to exploit the readily available 1-bromoallyl complex and its congeners as starting materials in Kumada type coupling6 of 68 with carbanionic reagents in the presence of nickel catalysts.
5
6
In the event, treatment of 6 with phenylzinc chloride in the presence of [1,3-bis(diphenylphosphino)propane]nickel(I1) chloride as catalyst gave 7a rather than the expected coupling product 8.
Fp
Fp-Ph
6
1Oa
9
4b
However, treatment of (2-bromo-2-buteny1)Fp(1 1) with phenylzinc chloride failed to yield any coupling product.
PhZnCl
Aph 4 AB' 8
than near 6 2.0, as would be expected for structure 8. The unexpected course of the reaction suggested that a process very different than the one anticipated had been followed and that the catalyst might not be essential. Indeed, this proved to be true, and the modest yield of 7a obtained in the presence of catalyst could be improved to 93% in its absence. Similarly conversion of (q'-methallyl)Fp 4b to a mixture of (2)-and (E)-bromomethallyl isomers 9 followed by reaction with phenylzinc chloride gave 10a as a mixture of geometrical isomers (Z/E = 3:l) in 61% yield.g
& FP
FPJB/r
FP
69
6 Z " C I
+
L+
Fp
11
7a
The unusual coupling product is obtained as a mixture of Z and E isomers (l:l), and its structural assignment is based on its 'H NMR spectrum which shows a two-proton resonance at 6 3.4 compatible with structure 7a, rather ( 5 ) Fabian, B. D.; Labinger, J. A. J. Am. Chem. SOC.1979,101, 2239. Labinger, J. A. J . Organomet. Chem. 1977, 136, C31. (6) Rosenblum, M.; Waterman, P. S. J. Organomet. Chem. 1980,187, 267. (7) Cutler, D.; Ehntholdt, D.; Lennon, P.; Nicholas, K.; Marten, D. F.; Madhavarao, M.; Raghu, S.; Rorran, A.; Rosenblum, M. J.Am. Chem. SOC. 1975, 97, 3149. (8) Kumada, M. Pure Appl. Chem. 1980,52, 669.
The coupling reaction appears to be a fairly general one for 6 and 9 with both aryl- and vinylzinc halides. Methylzinc chloride and the zinc salt of 2-methylcyclohexanone also couple with 6, but allylzinc chloride failed to react with this complex. Table I provides a summary of condensations carried out with 6 and 9. In general these reactions were run at room temperature in the presence of 2 equiv of the zinc reagent. Under these conditions, the (9) These may not represent kinetically determined ratios of product since the closely related CpFe(PPh,)(CO)(vinyl) complexes have been shown undergo facile cis to trans isomerization on heating. Reger, D. L.; McElligott, P. J. J. Am. Chem. SOC.1980, 102, 5923.
258 Organometallics, Vol. 5, No. 2, 1986
reaction is slow and requires 48 h for completion. As a means of probing the mechanism of the coupling reaction, we sought to prepare complex 6 specifically deuterated at C-1. Unexpectedly, these experiments provided evidence for yet another rearrangement process, which like the coupling reaction itself owes its operation apparently to the high mobility of the Fp group. Before proceeding to an account of these experiments, it is important to note, for the purpose of these discussions, that the diastereotopic methylene protons in 5 , the precursor to 6, show very different chemical shifts at 6 3.67 and 4.53, possibly as a consequence of their spatial relationship to the complexed double bond.'O These high- and low-field resonances may be assigned to H-3s and H-3R, respectively, from the observed coupling constants for each with H-2 ( J = 9.6 and 3.9 Hz, respectively). The conformational preference" for the unsaturated chain in the complex, shown in structure 12, is in turn based on exam-
-
Celebuski et al.
e +o + I
I
(3)
Thus, isomerization of the triflate salt is relatively slow at -20 "C, requiring several days for completion, but equilibration of the hexafluorophosphate salt is complete within 3 h a t this temperature. The stereospecific deuteration of 6 may be contrasted with the reaction of (7'-1-phenylallyl)Fp, which has been observed to undergo nonstereospecific deuteration in the presence of CF,COOD.7 Deprotonation of an equilibrated mixture of 5-d and 5-d', as the PF6salt, with diisopropylethylamine at 0 OC gave (q'-cis-l-bromoallyl)Fpwith deuterium incorporation only at C-3 and little loss in total deuterium content, by NMR analysis.
5-d
-+
5-d'
FP
Ur 6-d
12
ination of the I3C NMR spectra of a number of closely related 3-substituted Fp(q2-propene)cations, which suggests that the halogen atom in 5 is oriented so as to interact equally with both of the diastereotopic carbonyl l i g a n d ~ . ~ Deuteration of (ql-cis-l-bromoal1yl)Fp6 with deuteriotriflic acid gave an 89% yield of labeled product 5 - 4 isolated as the triflate salt by precipitation with ether. Proton NMR analysis showed a 50% incorporation of deuterium entirely by replacement of H-3R. The protonation of 6 is consequently highly stereospecific as is the reverse process, which proceeds through the removal of H-3Rin 5 by triethylamine to give exclusively the cis-1-bromoallyl isomer 6.' On standing in acetone solution at -20 "C for several days, 5-d undergoes stereospecific rearrangement to give trans-1-deuterio-3-bromoallyl complex 5-d' in equilibrium with 5-d.
-
The formation of 6-d as the sole product of the reaction is consistent with stereospecific deprotonation, which would be expected to result in selective removal of deuterium from 5-d. But the overall high retention of deuterium in the product requires that the rate of exchange of 5-d and 5-d' be faster than the rate of deprotonation and that the primary isotope effect for the deprotonation reaction be relatively large.12 The parallel reactions of (ql-methallyl)Fp 4b form a striking contrast to those of the parent complex 4a. While the sequence of bromination and deprotonation with the latter compound gives only the (2)-bromoallyl derivative 6, similar transformation of 4b gives 9 as a 3.5:l mixture of ZIE isomers. Br
I
Br
4b
13
(10) Jackman, L. M. "Nuclear Magnetic Resonance Spectroscopy",2nd ed.; Pergammon Press: Oxford, 1900; pp 83-88. (11) Faller, J. W.; Johnson, B. V. J. Organomet. Chem. 1975,88, 101.
F~T 9 -E
5-d
We suggest that the rearrangement proceeds through a concerted 1,3-migration of both the Fp and Br groups. Such a mechanism requires that rearrangement takes place through a higher energy conformation of 5 in which the C-Br bond is anti rather than syn to the Fp-olefin bond as depicted in 12. Such a conformation allows charge delocalization in the transition state to be shared by both Fp and Br groups moving concertedly across opposite faces of the C3 ligand. Moreover, such a mechanism accounts for the stereospecific transposition of deuterium label to give the trans-1-deuteriopropene complex 5-d' (eq 3). The equilibration of 5-d with 5-d' is accelerated on changing the gegen ion from CF,S03- to PF6-, which may reflect a rate dependence on ion pair association in the salt.
9-z
An examination of the proton NMR spectrum of the intermediate olefin complex 13 provides a rationale for this behavior. While the diastereotopic protons in 5 show disparate chemical shifts (A6 = 0.9 ppm), those in 13 are nearly identical. We attribute this to destabilization of a conformation for 13 similar to that shown for 5 (structure 12), due to steric interactions of the methyl substituent with cyclopentadienyl ring protons. Such interactions are relieved by rotation of the olefinic C-C bond axis out of a plane parallel to the cyclopentadienyl ring plane (Scheme 11),with the consequence that both HRand Hs may adopt a conformation, required for metal-assisted deprotonation, ~
~~
(12) Primary deuterium isotope ratios (kH/kD)as large as 7 have been observed in E2 reactions of 2-phenylethyl derivatives: Saunders, W. H.; Cockerill, A. F., "Mechanisms of Elimination Reactions";Wiley: New York, 1973; 79. The primary isotope effect for proton loss from the phenonium ion generated by protonation of 1,3,5-trimethoxybenne has the value of 9 Kresge, A. J.; Chiang, Y. J.Am. Chem. SOC.1967,89,4411.
Organometallics, Vol. 5, No. 2, 1986 259
Fp(s'-allyl) and Fp(s2-olefin) Complexes Scheme I1
+
9-1
-
F=
oc
-
9-E
trans to the Fp-olefin bond. In these circumstances, loss of HRyields the (cis-bromomethally1)Fpcomplex 9-27,while loss of Hs gives the trans isomer 9-E. Deuteration of 9-Z,E with CF3S03D in methylene chloride at -78 "C, followed by gegen ion exchange with NH4PF6gave 13-d with 75% incorporation of deuterium. D
I
for these complexes appear to be closely related to the present results. Fp(.r12-trans-ethyl-2-butenoate)BF4 (14), prepared from the epoxide by reaction with NaFp followed by treatment with HBF4.etherate, gave the sigmatropically transposed complex 15 on treatment with triethylamine. This latter substance reacted with bromine at -78 "C to give bromoallyl complex 17 rather than the anticipated isomeric complex 16. It seems likely that 16 is initially formed in the bromination reaction, but undergoes rapid 1,3-rearrangement to 17. The complex salt 17 was too unstable to characterize spectrally, but decoinposition in solution yielded the free ligand 18. Furthermore, deprotonation of the salt at low temperature gave the bromoester complex 19 as a mixture of Z and E isomers. These reactions serve &COOEt
-
FP
3Br
9-2; E
b C O Q E t
14
9-d
13-d
Proton NMR analysis of the product showed that all the deuterium was at C-3, in both diastereotopic positions. In contrast to 5-d, no scrambling of the deuterium label was observed when solutions of 13-d were left standing. It seems likely that the increased barrier to 1,3-transposition of bromine in 13-d compared with 5-d may be due in part to steric interactions of the methyl group at C-2 with the cyclopentadienyl ring in the transition state (eq 3). Moreover, the energy of the transition state compared with that for 5-d would be expected to be further increased by the need for partial Fe-C bonding to a tertiary carbon center. Deprotonation of 13-d with diisopropylethylamine in methylene chloride at 0 "C gave 9-d as a 2:l mixture of Z and E isomers, with 60% incorporation of deuterium. With specifically deuterated bromoallyl complexes 6-d and 9-d in.hand, coupling of each with phenylzinc chloride was examined. These reactions gave products 7a-d and loa-d, respectively, each of which corresponds to a 1,3transposition of the Fp group in the course of the reaction.
[ J C O O E J
-
-
Fp-COOEt
15 r
T
FOOEt
16
Brv FP
18
to illustrate the high mobility of the Fp substituent, in neutral (.rl'-allyl)Fp complexes as well as in Fp(v2-olefin) cations. However, the mechanisms by which these substances undergo rearrangement differ substantially. The allyl complexes rearrange by a radical chain s H 2 ' process, while the cationic bromoolefin complexes undergo 1,3-rearrangement through an ionic pathway involving concerted migration of halogen and the Fp group.
Experimental Section 70-d
6-d
I
9 -d
loa-d
These results may be accounted for by a sequence involving radical induced isomerization of starting materials in a preequilibrium reaction, which results in the conversion of relatively unreactive vinyl halides to reactive allyl halides. Reaction of these with the organozinc reagents by an SN2' process would be expected to take place rapidly. The relatively low overall rate of reaction may be attributed to a low concentration of the rearranged allylic halide intermediates in equilibrium with starting complexes, while the failure of the butenyl complex 11 to react is apparently due to increased retardation of the SH2' processes by the methyl substituent. Some earlier observations, made in the course of examining the reactions of F p crotonate complexes, deserve comment at this point, since the rearrangements observed
All reactions and subsequent manipulations of organometallic compounds were performed under argon atmosphere. Solvents used, except for diethyl ether (ether)and tetrahydrofuran (THF), were deaerated by bubbling argon through the solvent. Ether and THF were freshly distilled immediately before use from Na-benzophenone ketyl solutions. Unless otherwise noted, reactions were run in Ar-filled rubber-septum capped flasks. Infrared spectra were run on a Perkin-Elmer 457 or 683 spectrophotometer in CH2C1, solution at a concentration of roughly 20 mg/mL. Proton magnetic resonance spectra were obtained by using a 90-MHz Varian EM-390 spectrometer, a Varian XL-300 spectrometer (NSF GU 3852), or a homebuilt 500-MHz spectrometer (NIH GM 20168). Carbon-13 magnetic resonance spectra were determined at 22.64 MHz on a Bruker WH-90 spectrometer (NSF GU 3852, GP 37156) and were obtained with broad-band decoupling. Chemical shifts were referenced to the center lime of CDC13(76.9 ppm). Mass spectra were recorded on a Hewlett-Packard GC/MS system, Model 5985. Combustion analyses were performed by Galbraith Laboratories, Knoxville, TN. Preparation of (E,Z)-l-Fp-3-phenylpropene (7a). To 285 mg (2.09 mmol) of ZnClz was added 20 mL of THF. The solution was cooled to -78 O C , and 0.88 mL of commercial (Aldrich) PhLi (2.3 M in 70/30 cyclohexane/ether, 2.03 "01) was rapidly added dropwise. Then, 289 mg (0.97 mmol) of 6' in 25 mL of THF was
260 Organometallics, Vol. 5, No. 2, 1986
Celebuski et al.
added via cannula. The dry ice bath was removed, and the 3.3 H, Cp trans), 2.3-1.4 (br m, 10 H, CH,), 0.94 (s, 3 H, Me). Anal. reaction mixture was left to stir at ambient temperature for 48 Calcd for C1,H2,FeO3: C, 62.22; H, 6.14. Found: C, 62.47; H, 6.62. h. The mixture was quenched with 50 mL of saturated aqueous NaHC03, and to the resultant two-phase system in a separatory Attempted Reaction of 6 with Allylzinc Chloride. To 226 funnel was added 100 mL of ether. The combined organic extracts mg (1.66 mmol) of vacuum dried ZnC1, in 10 mL of THF was were back-washed with 50 mL of saturated aqueous NaHC03, added 0.83 mL of 2.0 M allylmagnesium chloride (1.66 mmol) in dried over MgS04,filtered, rotary evaporated to dryness, and then THF via syringe. Then, 226 mg (0.76 mmol) of 6 in 10 mL of THF vacuum dried. The crude material obtained had a weight of 276 was added to the solution via cannula. The cold bath was removed, and the mixture was stirred at ambient temperature for mg. This material was taken up as much as possible into petroleum ether and filtered through Celite on a glass wool plug. 48 h. After standard workup and filtration of the crude petroleum The solvent was stripped off, and the residue was vacuum dried ether extract through Celite, 114 mg of the starting alkenyl to give 265 mg of product 7a as a red oil (93%). The crude product bromide 6 was isolated (50% recovery). was purified by preparative TLC on alumina plates (petroleum Reaction of 6 with MeZnC1. Preparation of 7e,f. To 250 ether), but good elemental analyses could not be obtained since mg (1.83 mmol) of vacuum-dried ZnCl, in 20 mL of THF at -78 the product decomposed on brief storage: IR (CH2C1,),Y 2004, "C was added 1.37 mL of 1.30 M MeLi (1.78 mmol) in ether via 1951 (CO), 1599 (Ph) cm-'; 'H NMR (CS,) 6 7.10 (br m, 5 H, Ph), syringe. Then, 254 mg (0.85 mmol) of 6 in 20 mL of THF was 6.33 (dt, 1 H, J = 15.3, 1.4 Hz, H-l), 5.58 (dt, 1 H, J = 15.3, 6.2 added to the MeZnCl solution via cannula. The cold bath was Hz, H-2), 4.67,4.70 (ZS, 5 H, Cp), 3.40 (dd, 2 H, J = 6.2, 1.4 Hz, removed, and the mixture was stirred at ambient temperature benzyl); 13C NMR (CDCl,) 6 40.5, H 45.1 (2)-and (E)-CH,Ph), for 48 h. After standard workup 145 mg of a yellow oil was 85.2,85.5 (Cp) 122.6, 125.2, 125.9, 126.3, 126.9, 127.3, 127.6, 128.0, obtained (75%). Proton NMR analysis showed a mixture of four 128.1,142.0, 142.9,144.8,(Ph, vinyl) 215.7 (MCO); mass spectrum Cp-containing materials. (2)- and (E)-l-Fp-2-butene were (70 eV), m / e (fragmentation, relative intensity) 294 (M, L6), 266 identified as two of the four compounds by comparison with a (M - CO, 10.6), 238 (M - 2C0, 71.1). spectrum of the authentic materials. The other two Cp containing Preparation of (E,Z)-l-Fp-3-(2,5-dimethoxyphenyl)- materials were identified as (2)- and (E)-Fp-1-butenefrom analysis propene (7b). To 290 mg (2.1 mmol) of p-dimethoxybenzene of the NMR spectrum. 'H NMR (CS,): (l-Fp-2-butene),6 5.8-4.8 in ether at room temperature was added 1.21 mL of 2.6 M n-BuLi (m, 2 H, vinyl), 4.67, 4.60 (29, 5 H, Cp), 2.2-1.9 (m, 2 H, CH,), (3.15 mmol) in hexane. The mixture was stirred for 24 h at 1.53 (d, 3 H, J = 7 Hz, Me); (1-Fp-1-butene),6 6.3-6.0 (m, 1 H, ambient temperature. The yellow solution of l-lithio-2,5-diFpCH), 5.7-5.4 (m, 1 H, vinyl), 4.78 4.70 (2s, 5 H, Cp), 2.2-1.9 methoxybenzene was added via cannula to solution prepared from (m, 2 H, CH,), 0.9 (t, 3 H, J = 7 Hz, Me). 327 mg (2.4 mmol) of ZnCl, in THF and cooled to -78 "C. Then, Preparation of (E,Z)-l-Fp-2-methyl-3-phenylpropene 315.1 mg (1.05 "01) of 6 in 10 mL of THF was added via cannula. (loa). To 351 mg (2.57 mmol) of vacuum-dried ZnC1, was added The cold bath was removed, and the mixture was left to stir a t 10 mL of THF. The solution was cooled to -78 "C, and 1.1mL ambient temperature for 46 h. Solid C02 was added, followed (2.54 mmol) of 2.3 M PhLi in 70/30 cyclohexane/ether was added by 100 mL of saturated aqueous NaHC03. After the standard via syringe. To the in situ generated PhZnCl was added 376 mg workup, 482 mg of crude material was isolated. Filtration of a (1.21 mmol) of 9 in 15 mL of THF via cannula. The cold bath petroleum ether solution of the crude product through Celite, was removed, and the reaction mixture was left to stir for 42 h. followed by preparative TLC (1-mm alumina plate, petroleum After standard workup (see above), extraction of crude product ether eluent) gave 91 mg of 7b (24%): IR (CH2C1,),Y 2011,1962 with low-boiling petroleum ether, and filtration through Celite, cm-' (CO); 'H NMR (CS,) 6 7.0-6.0 (m, 4 H, H-1, aryl), 5.50 (dt, 523 mg of red oil resulted. The oil was purified by preparative 1 H, J = 15.8, 7.0 Hz, vinyl), 4.78, 4.73, (29, 5 H, Cp) 3.8-3.6 (49, TLC (1mm alumina plates, petroleum ether eluent) to give, upon 6 H, OMe), 3.28 (d, 2 H, J = 7 Hz, benzyl); mass spectrum (20 extraction of the yellow band with ether, 230 mg of yellow oil eV), m / e (relative intensity) 354.2 (M, L3), 326.1 (M - CO, 7), (61%). This material like 7a decomposed on standing briefly and 297.9 (M - 2C0, base). Anal. Calcd for C18HlBFe04:C, 61.04; could not be analyzed: IR (CH2C12)vma 2006,1956 (CO), 1600 H, 5.12. Found: C, 60.87; H, 5.35. (Ph) cm-'; 'H NMR (CS,) 6 7.04 (m, 5 H, Ph), 6.03 (s, 1 H, vinyl), 4.75, 4.73 (two s, 5 H Cp), 3.40 (s, 2 H, benzyl), 1.67, 1.53 (two Preparation of (E)-l-Fp-1,4-pentadiene(7c). To 327 mg s, 3 H, Me); 13CNMR (CDCl,) S 21.8, 27.4 (E- and 2-CHJ, 44.4, (2.4 mmol) of vacuum dried ZnClz in 15 mL of T H F at -78 OC 50.8 (2-and E-CH,Ph), 85.3, 85.5 (E- and Z-Cp), 117.8, 118.1, was added 2.32 mL of 1.0 M vinylmagnesiumbromide (2.32 m o l ) 122.7, 125.4, 125.8, 126.9, 127.1, 127.3, 127.6, 127.8, 128.0, 128.3, in T H F via syringe. Immediately, a white precipitate formed. 128.5, 141.0, 141.2, 144.8, 145.9, 146.1 (Ph, vinyl), 216.0 (MCO). Then, 331 mg (1.11 mol) of 6 in 20 mL of T H F was added via Preparation of (E,Z)-l-Fp-2-methyl-3-(2,5-dimethoxycannula. The cold bath was removed, and the suspension was pheny1)propene (lob). To 290 mg (2.1 mmol) of p-dimethstirred at room temperature for 48 h, whereupon the suspension oxybenzene in ether at room temperature was added 1.21 mL of clarified. After the standard workup, 269 mg of crude material 2.6 M n-BuLi (3.15 mmol) in hexane. The mixture was stirred was isolated. After extraction of this material with petroleum for 24 h at ambient temperature. To the yellow ether solution ether and Celite filtration of the resultant suspension, 196 mg was added 30 mL of THF, followed by 327 mg (2.4 mmol) of ZnC12. (73%) of 7c was isolated as a yellow oil. Combustion analysis The yellow solution turned colorless. The mixture was cooled was precluded by sample decomposition: IR (CH2C12):,Y 2012, to -78 OC, and 383 mg (1.23 mmol) of 9 in 15 mL of THF was 1960 cm-'. 'H NMR (CS,): 6 6.19 (dt, 1 H, J = 15.2, 1.0 Hz, H-l), added via cannula. The cold bath was removed, and the reaction 5.55 (m, 1 H, H-4), 5.17 (dt, 1 H, J = 15.2, 6.3 Hz, H-2), 4.9-4.6 mixture was stirred at ambient temperature for 48 h. Workup (m, 2 H, H-5), 4.75 (s, 5 H, Cp), 2.80 (t, 2 H, CHJ. Preparation of (E,Z)-l-Fp-3-(2-methyl-l-oxo-2-cyclo- gave 110 mg of product (24%);NMR analysis indicated that the product was roughly an equal mixture of geometric isomers. IR hexy1)propene (7d). A solution of 419 mg (2.29 mmol) of 1(CH,Cl2): vmu 2004, 1957 cm-'. 'H NMR (CS,): 6 6.6-6.2 (m, [ (trimethylsilyl)oxy]-2-methylcyclohexene in 10 mL of THF was 3 H, aryl), 5.93,5.88 (2s,1 H, vinyl), 4.70 (s, 5 H, Cp), 3.7-3.5 (3s, cooled to 0 "C, and 0.97 mL of 2.6 M n-BuLi (2.52 mmol) in hexane 6 H, OMe), 3.29 3.23 (2s, 2H, benzyl), 1.67, 1.47 (2s, 3 H, Me). was added in five equal portions over 10 min. The reaction Mass spectrum (70 eV); m / e (relative intensity) 368 (M, 0.4), 340 mixture was stirred at 0 OC for 1h, and then 343 mg (2.52 mmol) (M - CO, 4.5), 312 (M - 2C0,61.6). Anal. Calcd for Cl9H2&'eO4: of solid ZnClz was added. Upon solution of the ZnCl,, the mixture C, 61.98; H, 5.47. Found: C, 61.93; H, 5.63. was cooled to -78 "C, and 370 mg (1.24 mmol) of 6 in 10 mL of Preparation of l-Fp-2-methyl-1,I-pentadiene (1Oc). To 406 THF was added via cannula to the organozinc reagent. The cold mg (2.98 mmol) of vacuum-dried ZnCl, in 15 mL of THF at -78 bath was removed, and the reaction mixture was left to stir at "C was added 2.98 mL (2.98 mmol) of 1.0 M vinylmagnesium ambient temperature for 46 h. After standard workup and pebromide in T H F via syringe. Immediately, a white precipitate troleum ether Celite filtration, 410 mg of a viscous yellow-red oil formed. Then, 463 mg (1.49 mmol) of 9 in 20 mL of THF was was obtained (100%). NMR analysis indicated a 1.92/1.0 ratio added via cannula. The cold bath was removed, and the susof the E / Z isomers. IR (CH2C12): umm 2010, 1960 (CO), 1703 pension was stirred at room temperature for 48 h, whereupon the (C=O) cm-'. 'H NMR (CS,) 6 6.15 (dt, 0.66 H, J = 15.3, 1.0 Hz, suspension clarified. After the standard aqueous bicarbonate FpCH trans), 5.73 (dt, 0.34 H, J = 6.8, 1.0 Hz, FpCH cis), 5.23 workup, 363 mg of crude material was isolated. After extraction (dt, 1 H, J = 15.3, 8.2 Hz, vinyl), 4.80 (s, 1.7 H, Cp, cis), 4.73 (s,
Fp(q'-allyl) and Fp(q2-olefin)Complexes of this material with petroleum ether and Celite and filtration of the resultant suspension, 266 mg (69%) of 1Oc was isolated as a yellow oil. Combustion analysis was precluded by sample decomposition. IR (CH2C12):u,, 2066,1957 cm-' (CO).'H NMR (CS,): 6 5.90 (t, 1 H, J = 0.8 Hz, H-11, 5.71 (m, 1H, H-4),4.86-4.6 (m, 2 H, H-5), 4.75 (s, 5 H, Cp), 2.76 (dd, 2 H, j = 6.9, 0.8 Hz, H-3), 1.59 (5, 3 H, Me). Preparation of Fp(~~-3-brom0-2-methyl-l-propene)BF, (13). (1sobutenyl)Fp (4b; 2.19 g, 9.4 mmol) was taken up in 30 mL of CH2C12and cooled to -78 "C. Bromine (0.49 mL, 9.0 "01) was added dropwise. Reaction was continued at -78 "C for 45 min, and then 1.30 mL (9.0 mmol) of HBF,.Et,O was added. The cold bath was removed, and the solution was purged of HBr by a stream of argon. Ether was added to precipitate the product, which was filtered off, washed with ether, and dried in vacuo. The yield of crude product isolated as a yellow solid was 3.29 g (88%). The material slowly decomposes at room temperature. 'H NMR (CDSNOZ, 0 "C): 6 5.60 (s,5 H, Cp), 5.17 (9, 1 H, CH=), 5.00 (9, 1 H, CH=), 4.06 (s, 2 H, CH,Br) 1.90 (s, 3 H, CH3). Preparation of (E,Z)-3-Fp-1-bromo-2-methylpropene(9Z,E). The salt 13 (3.24 g, 8.13 mmol) was stirred in 25 mL of CH2C12and cooled to 0 "C. Diisopropylethylamine (1.42 mL, 8.2 mmol) was added dropwise, and the reaction mixture was stirred a t 0" for 45 min. The reaction solution was allowed to come to room temperature, solvent was removed in vacuo, and the residue was extracted into petroleum ether. This was filtered through Celite. Removal of solvent left 2.06 g of product as a red oil (82%). 13C NMR (CDCl,): 6 2.20 (FpCH2,Z isomer) 8.00 (FpCH2,E isomer) 23.27 (CH,), 84.56, 85.49 (Cp, E and Z isomers), 94.61, 94.73 (CHBr, Z and E isomers), 151.65 (CMe=), 216.80 (CO). The ratio of Z/E isomers, based on the relative intensities of FpCH, resonances, was calculated to be 3.5. 'H NMR (CS2): 6 1.77 (s, 3 H, CH3) 2.03 (s,2 H, CHzFp), 4.75,4.60 (2 S, 5 H, Cp), 5.52 (q, CH=, Z isomer) 5.72 (m, CH=, E isomer). Preparation of Deuterated Fp(q2-3-bromo-1propene)F3CS03(5-d). To a solution of 344 mg (1.15 mmol) of 6 in 25 mL of CH2C12at -78 "C was added dropwise, via syringe 0.11 mL (1.26mmol) of CF3S03D,prepared from (CF3S02),0 and D20 at 60 "C for 3 h. The reaction mixture was stirred at -78 "C for 1h, and ether was then added to precipitate the product. The salt was filtered off and washed with ether until the washings were colorless. The product was then air- and vacuum-dried to give 461 mg of 5-d (89%). Proton NMR analysis of this material indicated a 50 A 5% incorporation of deuterium by replacement of HRexclusively (structure 12) as indicated by the loss in intensity of the signal at 6 4.53. Extended reaction periods (6 days) at -20 "C led to the scrambling of the label to give a 1:l mixture of 5-d and 5-d'as indicated by changes in integrations for methylene vinyl proton resonance at 6 4.12 and 3.83. 'H NMR of freshly prepared material (acetone-d,): 6 6.03 (5, 5 H, c p ) , 5.5-5.4 (m, 1 H, CH=), 4.53 (dd, 0.5 H, J = 3.8, 9.9 Hz, HR), 4.18 (d, 0.9 H, J = 8.2 Hz, CH,=), 3.83 (d, 1.0 H, J = 14.4 Hz, CH2=), 3.70 (t, 1.0 H, J = 9.9 Hz, Hs). Preparation of Deuterated Fp(~2-3-bromo-l-propene)PF6 (5-d/5-d'). The 461 mg of triflate salt (0.99 mmol) was slurried into acetone and cooled to -78 OC, and then 465 mg (2.85 mmol) of solid NH4PF, was added all at once. The cold bath was replaced with an ice water bath, and the slurry clarified. The acetone was stripped off on the rotary evaporator, and the residue was slurried into cold distilled water. The salt was filtered off and washed with cold water, and then the solid was taken up into acetone. Precipitation was effected with ether. Filtration and ether washing of the precipitate gave a 90% yield of yellow PF,. NMR analysis established that the D label was located mostly a t C-3. Upon leaving the NMR solution stand at -20 "C for 3 h, the deuterium label scrambled into the H-lc position such that the composition of 5-dI5-d'in the mixture of the produch was 50150. There was a total of 45 f 5% D in the molecule, by NMR integration, using the Cp resonance as internal standard. 'H NMR (Acetone-d,): freshly prepared material, 6 6.03 (s, 5 H, Cp), 5.6-5.3 (m, 1 H, methine), 4.57 (dd, 0.68 H, J = 9.9, 3.8 Hz, CHD), 4.19 (d, 0.89 H, J = 8.2 Z, cis-CH2=), 4.0-3.5 (m, 2 H, trans-CH2=, CHD); after 3 h, 6 6.03 (s,5 H, Cp), 5.6-5.1 (m, 1H, methine), 4.57, (dd, 0.78 H, J = 9.9, 3.8 Hz, CHD), 4.19 (d, 0.78 H, J = 8.2 Hz, cis-CH2=), 3.89 (d, 1 H, J = 14.6 Hz, trans-CH2=), 3.70 (t, 1H, J = 9.9 Hz, CHD).
Organometallics, Vol. 5, No. 2, 1986 261 Preparation of 1-Bromo-3-deuterio-3-Fp-propene (64). A sample of 491 mg (1.1mmol) of 50 f 5% monodeuterated 5-d/5-df (by NMR integration) was slurried into 15 mL of CH2Clz and cooled to 0 "C. Diisopropylethylamine (0.19 mL, 1.1mmol) was syringed dropwise into the 'suspension, and the reaction mixture was stirred at 0 "C for 50 min. The solvent was stripped off via rotary evaporation, and the residue was taken up into a minimal amount of CH2C12and applied to a 1 mm alumina prep TLC plate. Elution with petroleum ether gave a yellow band which was extracted with ether to give 218 mg of the desired as a yellow oil, 50 f 5% labeled, with the deuterium label exclusively located at C-3 of the complex. 'H NMR (CS,): 6 6.22 (m, 1 H, H-2), 5.70 (d, 1 H, J = 7.5 Hz, H-l), 4.77 (5, 5 H, Cp), 1.92 (br d, 1.40 H, J = 9 Hz, FpCH2). Preparation of (E)-l-Fp-3-deuterio-3-phenylpropene (7a-d). To 227.4 mg (1.67 mmol) of ZnC1, in 15 mL of THF at -78 "C was added 0.64 mL of 2.4 M PhLi (1.52 mmol) solution via syringe. To the in situ generated PhZnCl was added 217.7 mg (0.72 mmol) of 50% monodeuterated 6-d in 10 mL of T H F via cannula,and the cold bath was removed. The reaction mixture was left to stir at ambient temperature for 48 h. After standard workup and petroleum ether extraction and filtration procedure 98.9 mg of dark red oil was isolated. This was chromatographed on a 1 mm preparative TLC plate (alumina, petroleum ether) to give, upon ether extraction of the yellow band, filtration, and solvent removal, 68.9 mg (32%) of the title compound. Integration analysis of the proton NMR spectrum shows that the product was 45 A 5% monodeuterated in the benzylic position. IR (CH2C1,): ,U 2012,1961 (CO), 1600 (Ph) cm-'. 'H NMR (CS,): 6 7.1-6.9 (m, 5 H, Ph), 6.31 br d, 1 H, J = 18 Hz, H-l), 5.7-5.2 (m, 1 H, H-2), 4.72 (9, 5 H, Cp), 3.31 (br d, 1.55 H, J = 7.4 Hz, benzyl). Preparation of Fp(q2-3-bromo-3-deuterio-2-methylprOpene)PF,(13-d). To 809.3 mg (2.60 mmol) of 9-Z$ in 20 mL of CHZClzat-78 "C was added 0.24 mL (2.8 mmol) of CF3S03D dropwise via syringe. The reaction mixture was stirred at -78 "C for 1h. Ether was added to precipitate the triflate salt at -78 "C. The solid was allowed to settle, and the supernatant was removed via careful cannulation. The solid remaining was slurried into acetone at -78 "C, and 1.37 g (8.4 mmol) of NH4PF6was added. In a few minutes, the slurry clarified to a clear red solution. The acetone was then stripped off in an ice bath. The resultant solid was slurried into cold distilled water and filtered. After the air-stable solid was washed with cold distilled water and air-dried, the solid was taken up into acetone and precipitated with ether. The light yellow solid was filtered, washed with ether, and airand vacuum-dried to give 604 mg of salt, 51% overall. Proton NMR analysis showed a deuterium content of 75% at the 3position of the olefin. IR (CH3CN): u,, 2070,2018 cm-I (CO). 'H NMR (CD3N02): 6 5.54 (s, 5 H, (Cp), 5.32 (s, 1H, vinyl), 4.95 (q, 1H, J = 2 Hz, vinyl), 4.10 (br s, 1.25 H, methylene), 1.72 (br s, 3 H, Me). Preparation of 1-Bromo-l-deuterio-2-methyl-3-Fp-propene (9-d). To a slurry of 204 mg (0.44 mmol) of 13-d in 20 mL of CH2C12at 0 "C was added 78 WL(57.5 mg, 0.44 mmol) of diisopropylethylamine via syringe. The suspension clarified in a few minutes to a red solution. The solvent was stripped off via rotary evaporation,and the residue was taken up into ether. The organic solution was filtered through Celite and stripped, and the residue was vacuum dried. This crude sample (137 mg) was chromatographed on a preparative TLC plate (petroleum ether, 1 mm alumina), and the yellow band was scraped and extracted with ether to give upon solvent removal 83 mg of a yellow oil, 60%. Proton NMR analysis indicated that the sample was 58 f 5% monodeuterated, and the deuterium was at C-1. The ratio of ZIE isomers, based on analysis of the 13Cspectrum of the product, was 2.0. IR (CH2C1,): ulnax 2006,1952 cm-' (CO). 'H NMR (CS2): Z isomer, 6 5.51 (q, 0.43 H, J = 1 Hz, vinyl), 4.78 (s, 5 H, Cp), 2.05 (9, 2.0 H, FpCH2), 1.79 (br s, 3.0 H, Me); E isomer, 6 5.70 (br m, 0.40 H, vinyl), 4.59 ( 8 , 5 H, Cp), 2.16 (s, 2.0 H, FpCHJ, 1.79 (br s, 3 H, Me). Preparation of (E)-l-Fp-2-methyl-3-phenyl-l-deuteriopropene (loa-d). To 188 mg (1.38 mmol) of ZnClz in 15 mL of THF at -78 "C was added 0.6 mL (1.31 mmol) of 2.2 M PhLi via syringe. Then, 204 mg (0.66 mmol) of 80 f 5% monodeuterated 9-d in 15 mL of T H F was added via cannula to the PhZnCl
262 Organometallics, Vol. 5, No. 2, 1986 solution. The cold bath was removed, and the mixture was left to stir at ambient temperature for 48 h. After the standard aqueous bicarbonate workup, 198 mg of crude material was isolated. Preparative TLC (1 mm alumina plate, petroleum ether eluent) gave 120 mg of a light yellow oil, 60% yield from the alkenyl bromide. Proton NMR integration analysis showed that the sample was 77 f 5% deuterated in the vinyl position. As in the case of nondeuterated analogue 9, combustion analysis was precluded by the fact that the sample decomposed on standing. Mass spectral analysis shows that the sample has a 73% deuterium content, by comparison of the M - 2CO peak intensities in the mass spectrum of the product. IR (CHpClz):umax 2010,1958 (CO), 1600 (Ph) cm-'. 'H NMR (CS,): 6 7.2-7.0 (m, 5 H, Ph), 6.04 (br s, 0.23 H, vinyl), 4.74 (s, 5 H, Cp), 3.40 (9, 2 H, benzyl), 1.61 (s, 3 H, Me). Mass spectrum (20 eV); m / e (relative intensity) 308 (M, 8.4), 280 (M - CO, 36), 252 (M - 2C0, loo), 251 (m - 2C0, 36.8). Preparation of (E)-Ethyl 4-Fp-2-butenoate(15). To a slurry of 1.16 g (3.08 mmol) of Fp(T2-ethy12-butenoate)BF,4in 15 mL of CH,Cl, at -23 "C was added 0.43 mL (3.10 mmol) of NEt, dropwise. The slurry became a solution in 5 min. The solvent was stripped off, and the residue was extracted into petroleum ether as much as possible. The petroleum ether extracts were filtered through Celite, and solvent was removed by rotary evaporation and vacuum drying to give 810 mg of the product as a dark oil: 93%; 'H NMR (CS2) S 7.05 (dt, 1 H, J = 15, 9.2 Hz, FpCHpCH), 5.37 (dt, 1 H, J = 15, 0.5 Hz, ROpCCH), 4.70 (9, 5 H, Cp), 3.96 (q,2 H, J = 7 Hz, OCHZ), 1.98 (d, 2 H, J = 9.2 Hz, FpCHJ, 1.18 (t,3 H, J = 7 Hz, MeO). Anal. Calcd for CI3Hl4FeO4: C, 53.82; H, 4.86. Found: C, 53.65; H, 5.02. Preparation of Fp(~2-(E)-ethy14-bromo-2-butenoate) (17). To 765 mg (2.64 mmol) of 15 in 15 mL of CHzC12at -78 "C was added 0.15 mL (2.9 mmol) of Br, dropwise via syringe. The mixture was stirred at -78 "C for 45 min, and then 0.36 mL (2.64 mmol) of HBF,-Et,O, was added via syringe. The cold bath was removed, and the reaction mixture was agitated by a rapid stream of Ar to remove HBr. A precipitate began to form. Ether was added to finish precipitation, and the yellow salt was filtered off and washed with ether. After air- and vacuum-drying, 969.5 mg of yellow-orange solid was obtained, 80%. Preparation of 3-(Ethoxycarbonyl)-3-Fp1-bromopropene (18). A suspension of 965 mg (2.11 mmol) of 17 in 10 mL of CHzClz was cooled to 0 "C. Then, 0.37 mL (2.11 mmol) of iPr,NEt was added dropwise, and the reaction mixture was stirred at 0 "C for 10 min. During this time, the suspension claified. The solvent was tripped off, and the residue was extracted into petroleum ether as much as possible. The petroleum ether extracts were filtered through Celite in a Schlenk tube, and the extracts were rotary evaporated and vacuum dried to give 741 mg of red
Celebuski e t al. oil, 95%. Proton NMR analysis showed a Z / E ratio of 3.43/1.0. IR (CH2C12):u- 2017,1976 (CO), 1682 (C=O) em-'. 'H NMR (CS,): 6 6.45 (dd, 0.77 H, J = 11,7.3 Hz, vinyl-Z), 6.45-6.22 (m, 0.23 H, vinyl-E), 5.79 (d, 0.23 H, J = 14 Hz, CHBr-E), 5.58 (dd, 0.77 H, J = 7.3, 1 Hz, CHBr-Z), 4.76 (s, 3.9 H, Cp-Z), 4.64 (s, 1.1 H, Cp-E), 3.89 (4, 2 H, J = 7 Hz, -OCHp), 3.31 (dd, 0.77 H, J = 11, 1.0 Hz, FpCH-Z), 2.82 (d, 0.22 H, J = 9.6 Hz, FpCH-E), 1.16 (t, 3 H, Me). Anal. Calcd for C13HI3BrFeO4:C, 42.32; H, 3.55. Found: C, 42.31; H, 3.67. Decomposition of Complex 17. The crotonate salt 14 (1g) was taken up in 8 mL of CHzClz and cooled to -40 OC. Triethylamine (0.21 g) in 2 mL of CH2Clpwas added dropwise, and stirring was continued for 30 min. Bromine (0.36 g) in 2 mL of CHZCl2was then added, and reaction was continued for an additional 20 min. The solution was then allowed to come to room temperature, during which time, the color of the solution changed from yellow to dark red, indicative of the formation of FpBr. Solvent was removed, and the residue was extracted with ether and filtered through Celite. The procedure was repeated by using light petroleum ether. Solvent was removed, and the residue was distilled in a Kugelrohr at 58 "C/2 min to give 0.33 g (83%) of product as a near colorless oil: NMR (CS,) 6 6.95 (dt, 1 H, J = 8, 15 Hz, P-CH=), 6.0 (d, 1H, J = 15 Hz, a-CH=), 4.16 (9, 2 H, OCHJ, 4.04 (d, 2 H, CH2Br), 1.28 (t, 3 H, CH,). Preparation of 4-Fp-2-bromo-2-butene( 1 1). To a -78 "C of 1-Fp-2-butenein 20 mL of CH2ClZ solution of 1.18 g (5.09 "01) was added 0.26 mL (5.1 mmol) of Brpvia syringe. The reaction mixture was left to stir at -78 "C for 1 h and then diluted with 5 mL of acetone. Next, solid HN4PF, (2.5 g, 5.3 mmol) was added all at once. The mixture was stirred vigorously for 10 min at -78 "C, and then the solvent was stripped off. The solid residue was slurried into cold distilled water and filtered. The filter cake was washed with water and air-dried. The resultant dark yellow solid was taken up into a minimal amount of acetone and precipitation effected with ether. The yellow solid was filtered off and washed with ether until the washings were clear. The solid was then airand vacuum-dried. This gave 1.71 g of Fp($-3-bromo-l-butene)PF, as a yellow solid, 74%. The sample decomposed upon dissolution in CD3NO2for NMR analysis. Deprotonation of this material with DBU and flash chromatogrpahy on a silica gel column of the product (15/1 cyclohexane/EtOAc) gave a 20% overall yield of product. i-Pr,NEt and NEt3 were ineffective in deprotonating the salt. 'H NMR (CS,): 6 5.70 (tq, 1 H, J = 8.7, 1.5 Hz, vinyl), 4.73 (s, 5 H, Cp), 2.12 (d, 3 H, J = 1.5 Hz, Me), 1.99 (d, 2 H, J = 8.7 Hz, FpCHp).
Acknowledgment. This research was supported by a grant from the National Science Foundation (CHE 8117510), which is gratefully acknowledged.
