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Asymmetric Induction in the [2 3] Wittig Rearrangement by Chiral Substituents in the Allyl Moiety.

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A second sharp singlet of equal intensity at 6=6.2
( w ' , ~ = 12 Hz) is attributed to the cation [(HB(pz*),12Al]@.
Interestingly, the reaction of K[HB(pz*),] with InCI3
took a different course and afforded the covalent dichloride 3. An X-ray crystal structure determination of
M. R. Churchill, J. C. Fettinger, J. C. Pazik, L. Victoriano, J . Am. Chem.
SOC.I08 (1986) 4666, and references therein.
121 A. H. Cowley, R. L. Geerts, unpublished results.
131 S. Trofimenko, Prog. Inorg. Chem 34 (1986) 115.
[41 B. R. McCarvey, M. J. Taylor, D. G. Tuck, Inorg. Chem. 20 (1981)
2010.
[ 5 ] 1 : monoclinic, space group P2,/c (No. 14). Z = 4 ; u=10.796(6),
V=4330
b=27.272(2), C = 14.825(2)
/1=97.27(2)',
pcalcd=
1.406
gcm-', 3 " < 2 8 < 5 5 " (MoKnd=0.71069A,p=I5.28 c m - ' , 9879 unique
reflections collected, of which 3846 (1>3.a(I)) were used to solve (direct
methods) and refine (full matrix, least squares) the structure of I .
R=0.0558, R,, =0.0649. 3 : triclinic, space group Pi (No. 2). Z = 2 ;
~=8.125(2), b = 13.848(2), c = 14.574(2) A, a=72.34(1), /1=74.76(2),
P ' . , , ~ ~ =1.295 gcm-', 3 < 2 0 1 4 8 " (MoK,
y=70.24(2)", Y=1447
A=0.71069 A), p = 10.07 c m - ' ; 4520 unique reflections, of which 3457
(I>3.0(0) were used to solve (Patterson) and refine (full matrix, least
squares) the structure of 3. R=0.0386, R,, =0.0492. Further details of
these crystal structure investigations can be obtained from the Fachinformationszentrum Energie Physik Mathematik GmbH, D-7514 EggensteinLeopoldshafen 2 (FRG), by quoting the depository number CSD-52 7 17,
the names of the authors, and the journal citation.
161 J. W. Akitt, Annu. Rep. NMR Spectrosc. 5 (1972) 465.
A,
[HB(pz*),]InC12 3
3.CH3CN'51revealed that each indium atom is bonded to
two chlorines and four nitrogens (Fig. 2). Three of the nitrogens are associated with the pyrazolylborato ligand, the
fourth being from a coordination CH3CN molecule. The
binding of the (CH3CN)InCI2 moiety to the pyrazolylborate face is not symmetrical as indicated by the fact that
the In-N21 distance is somewhat shorter than the other
two In-Npyra701yl
distances.
A,;
A,,
Asymmetric Induction in the
[2,3] Wittig Rearrangement by Chiral Substituents
in the Ally1 Moiety**
By Reinhard Briickner* and Henning Priepke
W
Fig. 2. Structure of 3 in the crystal. Selected bond lengths [.&I: In-CI1
2.428(2), In-C12 2.429(2), In-NI 2.379(7), In-Nl I 2.268(4), In-N21 2.233(6),
In-N31 2.249(5).
Recently, the Wittig rearrangement of allyloxy carbanions (1 + 2) has attracted renewed interest in terms of developing novel methodologies for stereoselective C-C
bond formation."' The relative configuration of the newly
formed stereogenic centers ("stereocenters") is influenced
by the configuration of the double bond in the allyl ether 1
and by the R5 moiety; the absolute configuration of the
newly formed stereocenters has been controlled so far by a
stereocenter at C-3 of the educt or by a chiral substituent
Rs.".21 Here we describe two examples of high asymmetric
induction by a stereocenter in the R ' moiety.
Experimental
All operations were performed under dry, oxygen-free conditions.
1 : A T H F (150 mL) solution of QHB(pz*),] 131 (1.91 g, 5.7 mmol) was added
dropwise to a T H F (150 mL) solution of GaCI, (l.Og, 5.7 mmol) at room
temperature. After stirring the reaction mixture for 18 h, the solvent was removed in vacuo. The resulting solid residue was extracted with CH2C12
(2 x 100 mL) and filtered. Recrystallization from CH'CN afforded colorless
I in > 80% yields. 'H-NMR (90 MHz, CD,CN, 25°C) 6 = 1.13 (s, 18 H, arylCH,), 2.50 (s, 18 H, aryl-CH,), 5.90 (s, 6 H , aryl-H).
2 was prepared in the same manner as 1 except that CH2C12was employed
as the reaction solvent. Recrystallization from CH,CN afforded colorless,
microcrystalline 2 in virtually quantitative yield. 'H-NMR (300.15 MHz,
CDCI,, 25°C) 6= 1.07 (s, 18H, aryl-CH,), 2.56 (s, IXH, aryl-CH,), 5.88 ( s ,
6 H , aryl-H).
3 was prepared in the same fashion as 1. Recrystallization from CH,CN
afforded colorless, crystalline 3 in essentially quantitative yield. 'H-NMR
(300.15 MHz, C6D,, 25°C) 6=0.58 (s, CH'CN), 2.03 (s, 9 H , aryl-CH,), 2.80
( s , 9 H , aryl-CH,), 5.45 ( s , 3 H , aryl-H).
CAS Registry numbers:
1, 112439-51-7; 2, 112439-53-9; 3, 112439-54-0; 3 . CH,CN, 112439-55-1;
K[HB(pz*),], 17567-17-8; GaCI,, 13450.90-3; AICI,, 7446-70-0; InCI,, 1002582-8.
In the first example, the allyl ether 3, containing a double bond with trans configuration, was rearranged upon lithiation (Scheme l).I3] Due to the influence of the chiral
dioxolane ring, the new stereocenter was formed with a
diastereoselectivity of 86%. The configuration of this stereocenter in the major product 4 was determined by 'HN M R s p e c t r o ~ c o p yafter
' ~ ~ transformation to the lactone 6.
Upon irradiation of the C H 2 0 H resonance of 6, we observed a nuclear Overhauser effect (NOE) of 6% for the
CH=CH2 signal, which indicates a cis arrangement of the
vinyl and hydroxymethyl groups. In the isomeric trans lactone, a corresponding NOE was not observed.[51
The second example of the novel asymmetric induction
was found when we deprotonated the allyl ether 7,@'containing a double bond with cis configuration. The Wittig
rearrangement of the lithium enolate of 7 gave a 40% yield
of only one homoallylic alcohol, 8,"l along with <2% of
the other three possible stereoisomers (Scheme 2). The
[ I ] a ) H. Schmidbaur, U. Thewalt, T. Zafiropoulos, Organometalhcs 2 (1983)
1150; b) Chem. Ber. 117(1984) 3381; c) J. Ebenhoch, G. Muller, S. Riede,
H. Schmidbaur, Angew. Chem. 96 (1984) 367; Angew. Chem. I n t . Ed.
Engl. 23 (1984) 386: d) ibid. Angew. Chem. 97 (1985) 893: Angew. Chem.
Int. Ed. Engl. 24 (1985) 893. For somewhat related chemistry of C5H5and Me5C5-substituted In' and TI' compounds, see, e.g., H. Werner, H.
Otto, H. J. Kraus, J . Organomel. Chem. 315 (1986) C57; 0. T. Beachley,
[*I Dr. R. Briickner, H. Priepke
Fachbereich Chemie der Universitat
Hans-Meerwein-Strasse, D-3550 Marburg (FRG)
[**I This work was supported in part by the Deutsche Forschungsgemeinschaft (Project Br 881/2-1). R. B. thanks the Fonds der Chemischen I n dustrie for a Liebig-Stipendium.
Received: September 7, 1987 [Z 2425 IE]
German version: Angew. Chem. 100 (1988) 306
278
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Angew. Chem. I n t . Ed. Engl. 2 7 (1988) No. 2
n&
3
4 (79%)
5 (6%)
b) - d)
energy more than the latter. Consequently, in the preferred transition state 11 of the Wittig rearrangement, the
C-0 bond of the ally1 substituent is perpendicular to the
plane of the double bond; of the remaining allylic substituents, the larger is found “outside” for steric reasons.
We therefore propose that 12 and 13 are transition
states for the Wittig rearrangements 3-4 and 7 - 8 , respectively. Here, the bulky heterocycle prefers the “outside” position and the H atom the “inside” position.[’’
6
Scheme 1. a ) 0.2 M in THF; + 2 equiv. 1.5 M nBuLi in hexane, -78”C, 1 h. b)
nBulP, Ph&. CH2C1z, room temp., 4 h ; 84%. c) LiNaphth/THF, then
CIC0,Me. both 7 8 ° C 30 min; 29%. d) Ref. [ 5 ] ; 49%.
~
<‘
acceptor
configuration of the stereocenters of 8 was determined
after conversion to the diol 9. Glycol cleavage and reduction lead to compound 4 mentioned above; hence, C-3 has
the (S) configuration in 9 and 8 . The configuration of C-2
of 8 was obtained after transformation of the diol 9 into
the bisacetonide 10 ; this compound is optically inactive
and displays only one set of signals for the two dioxolane
rings in both the ‘H- and I3C-NMR spectra. This means
that 10 contains a symmetry plane, which, in turn, proves
the ( R ) configuration of C-2 in 8.
12
11
\
13
Cha et al. investigated the Claisen-Ireland rearrangements related to the Wittig rearrangements described here,
but they found lower asymmetric inductions by the chiral
dioxolanes.[’’] A possible explanation is that, in the rearrangement of the neutral ketene acetal, less charge has to
be stabilized in the transition state by the
orbital than
in the rearrangement of the carbanions.
Thus, the reactions 3-4 and 7 - 8 represent a novel
stereocontrol in the Wittig rearrangement, which can be interpreted by a Felkin-Anh-type transition state 11. Compounds 4 and 8 are needed for the synthesis of amphotericin B.
Received: July 15, 1987;
Final version: November 26, 1987 [Z 2357 IE]
German version: Angew. Chem. 100 (1988) 285
Scheme 2. a) 0.2 M in T H F to 1.25 equiv. 0.2 M lithiumdiisopropylamide,
-78”C, 30 min; then 5.5 equiv. tetramethylethylenediamine, -4O”C, 3 h ;
40%. b) LiAIHdTHF; 92%. c) I . NaIO,/aq. MeOH, 2. NaBHJEtOH; 58%.
d) MeZC(OMef2,acetone, p-TsOH; 76%.
We observed the same 1,2-asymmetric induction in both
Wittig rearrangements, in 3-4 as well as in 7-8. The
vinyl group of the preferred rearrangement product is syn
to the C - 0 bond at the stereocenter originally present.
This finding becomes plausible by examining the reaction
path with the lowest-energy transition state in the frontier
orbital model. For this purpose, the Wittig rearrangement
is regarded as an SN2‘nucleophilic attack o n an allylic ether. The crucial orbital interaction occurs between the
HOMO,,,,, m O I C I Y and the LUMOal,yle t h e r molecy, whereby the
latter approximately can be taken as the z& orbital. The
energy of the n& orbital is lowered through overlap with
the adjacent allylic (T*orbitals,[81such as are present in the
dioxolane ring of 3 and 7. The lower in energy the
nCzc orbital thereby becomes, the better is the HOMO/
LUMO interaction in the transition state and the faster is
the [2,3]-sigmatropic rearrangement. Since a o E - ~orbital is
orbital, the former lowers the
lower in energy than a
orpC
Angew. Chem. Int. Ed. Engl. 27 (1988) No. 2
[I] Review: T. Nakai, K. Mikami, Chem. Reu. 86 (1986) 885.
121 a) M. Uchikawa, T. Hanamoto, T. Katsuki, M. Yamaguchi, Tetrahedron
Lett. 27 (1986) 4577; b) M. Uchikawa, T. Katsuki, M. Yamaguchi, ibid.
27(1986) 4581.
[3] Method: W. C. Still, A. Mitra, J. A m . Chem. Soc. 100 (1978) 1927.
The stannyl ether 3 ([a]?(c= 1.63, CDC13)+ 11.2) was prepared in 60%
yield from (4’S)-trans-3-(2,2-dimethyl-1,3-dioxolan-4-yl)prop-2-en-I-o1
([alg(c=6.37, CH2C12)+23.7; Ref. [ 5 ] : [alD(c=0.21, CHC13) +26.7; N.
Minami, S. S. KO, Y. Kishi, J . Am. Chem. Soc. 104 (1982) 1109: [a],,
(c=3.63, CHCI,) +33.9) by treatment with KH/Bu3SnCHZI.
141 4 : [ a l p (c= 1.26, CDCI,)
13.9. 300-MHz ‘H-NMR (CDCI,): S= 1.30
and 1.36 (2s; 2’-(CH&), 1.89 (dd, J=7.0, J=5.0; OH), 2.39 (mc; 2-H),
3.59-3.70 (m; I-Hz and S‘-H’), 3.97 (dd, J,,,,,=8.2, Js..np.4.=6.4; S‘-H’),
4.22(ddd, Jq.s-~1=541,5,~i=6.9,
Jc.2=4.6;4’-H), 5.15(ddd, J,,#,,,,=17.3.
J,..,=
1.7, J,,~=0.8; Z-4-H), 5.22 (dd, J,,,= 10.4, JqeflX=
1.7; E-4-H). 5.75
(ddd,J,,,,,,=17.3, J,,,=10.4, J3,2=8.7; 3-H).
[SI The cis lactone 6 and its trans isomer have been described: T. Suzuki, E.
Sato, S. Kamada, H. Tada, K. Unno, T. Kametani, J. Chem. Soc. Perkin
Trans. I 1986. 387; T. Kametani, T. Suzuki, M. Nishimura, E. Sato, K.
Unno, Heterocycles 19 (1982) 205. Thc configurational proof given by
the authors is not convincing in our opinion.
161 The ester 7 ([a]&’ (c=4.02, CHICL)
1.2) was obtained in 89% yield
from (4‘S)-cis-3-(2,2-dimethyl-I,3~dioxolan-4-yl)prop-2-en-l-ol([a]:;’
(c=2.42, CHzC12) 13.5; Ref. 151: Ialo (c=O.34, CHCI,)
17.1; N. Minami, S. S. KO, Y . Kishi, J. A m . Cbern. Soc I04 (1982) 1109: [a]&,
(c=4.52, CHCI,) + 14.0) by the sequence I . dimsyl-Na; CICH2C02Na,
2. CHINZ.
171 8 : [a]&’ (c=5.36, CHZCI2) -25.7. 300-MHz ‘H-NMR (CDC13): 6 = 1.37
and 1.42 (2s; 2‘-(CH3)2),2.65 (ddd, J3,=9.4, J’=6.2,5”=2.6; 3-H), 3.12
(d, J=4.6; OH), 3.78 ( S ; OCH,), 3.85 (dd, J,,,=S.I. JS,~H,.4,=7.1;5’-H’),
4.10 (dd, J,,,=8.2, J5..H2.4.=6.2; 5’-H’), 4.33-4.39 (m; 2-H, 4’-H), 5.15
(ddd, J,,,,=17.2,
J,,,,=1.7,
Js.,=O.7; Z-5-H), 5.25 (dd, J,,,=10.4,
Jqem = 1.8; E-5-H), 5.87 (ddd, J,,.,=
17.2, J,,.= 10.3, J4,3=9.5; 4-H).
[PI K. N. Houk, M. N. Paddon-Row, N. G. Rondan, Y.-D. Wu, F. K.
Brown, D. C. Spellmeyer, J. T. Metz, Y. Li, R. L. Loncharich, Science
231 (1986) 1108.
+
+
+
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+
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219
[9] The configuration of C-2 of 8 arises because in the transition state 13
the ester function gives way to the bulky dioxolane ring and therefore
occupies exchiuely the exo position (cf., however, Ref. [I]).-If the
dioxolane ring in 13 is replaced by the smaller methyl group, i.e., in the
transition state of the Wittig rearrangement of the (cis-crotyloxyfacetic
ester anion, the ester function is no longer forced completely into the ex0
position. Accordingly, the hydroxy ester resulting in /his case, contrary,
to 8 , shows only a 2 : 1 preference for the syn arrangement of the hydroxyl group and the vinyl group [2bj.
[lo] J. K. Cha, S. C. Lewis, Tetrahedron Lett. 25 (1984) 5263.
Na3PZI.The addition of dimethylformamide effects stabilization, whereas hydrocarbons or active charcoal cause immediate decomposition.
Characterization. The composition and structure of 1
were corroborated by extensive spectroscopic characterization of the NaP5/[18]crown-6/THF solutions. The 3'PNMR singlet appears at somewhat higher field (6=
+467.2) than in diglyme, corresponding to the larger polarity of the solvent mixture used.
The first determination of the ion mass of 1 in solution[41
was achieved by means of negative-ion FAB mass spectrometry. The use of method a) (cf. Ref. [5]) revealed, in
addition to ions of the solvent mixture, a species of mass
m / z 155 (PF) when the solution was warmed. This peak
disappeared upon further warming, while m / z 62 (PF) increased in intensity. After averaging of the separate spectra
obtained in the temperature region where m / z 155 appears
and subtraction of the spectrum of the solvent mixture recorded under the same conditions, the difference spectrum
exhibits (in addition to weak peaks corresponding to ions
of the series [(CH2),0,f HI', due to incomplete subtraction) only the phosphorus-containing species PF, PF, and
PzOe ( m / z 78, oxidation upon admission of the sample).
The use of method b) (cf. Ref. [5]) resulted in the immediate transient appearance of the PF ion with high intensity in addition to the matrix ions.
In the IR and Raman spectrum of the Nap, solution, an
intense band at 815 cm- ' (IR) and a medium-intense polarized band at 463 cm-' (Raman) are observed (in addition to the bands of the solvent mixture). These bands can
be assigned to the vibrational modes E; and A;, respectively, of a planar, five-atom ring of symmetry D,,
(102m).
The UV spectrum['] (Fig. 1) exhibits two n-n* bands of
medium intensity at 260 and 320nm as well as an n-n*
transition at 370 nm. When freshly prepared, dilute solutions ( c < l o w 4M) are employed, the 260-nm band shows a
vibrational fine structure with maxima at 271, 266, 258,
252, 246, and 241 nm. The low intensity of the longestwavelength vibronic maximum (271 nm) is an indication
for a symmetry-forbidden transition corresponding to
'A;+ 'E; of a 6n-electron system of the cyclopentadienide
type.17]Overall, the shape of the UV spectrum confirms the
aromatic character of 1.
Reactivity: The chemistry of 1 is characterized by analogies to and differences from that of the C,HF ion. For
instance, 1 reacts with alkyl halides to form, mainly, P,R3
On the PentaphosphacyclopentadienideIon, P:**
By Marianne Baudler, * Stilianos Akpapoglou,
Dimitrios Ouzounis, Fritz Wasgestian, Bernd Meinigke.
Herbert Budzikiewicz, * and Helmut Miinster
Dedicated to Professor Emanuel Vogel
on the occasion of his 60th birthday
We recently reported on the formation of the pentaphosphacyclopentadienide ion 1 upon cleavage of white phosphorus with sodium in diethylene glycol dimethyl ether
(diglyme) o r with lithium dihydrogen phosphide in tetrahydrofuran (THF); in addition, other polyphosphides (in
particular, M:Pl6, MiP,,, and MiP,,) were formed."]
Compound 1 was identified by a low-field singlet in the
"P-NMR spectrum (6= +470.2) and a singlet in both the
23Na-and 7Li-NMR spectra as well as by the Na :P ratio
of 1 : 5 determined analytically for solutions of Nap,. We
report here further findings that have been made in the
meantime concerning the formation, characterization, stability, and reactivity of 1 .
1
Preparation of apure Naps solution: The lithium salt was
the first alkali-metal pentaphosphacyclopentadienide that
could be obtained pure in solution."] In the case of the sodium compound, the other polyphosphides formed could
not be separated by crystallization from diglyme. As observed by chance,[*] the formation tendency of Nap, in
T H F is significantly increased by the presence of
[ 181crown-6, which simultaneously favors the precipitation
of other polyphosphides, so that a pure NaP,/[IS]crown6/THF solution can be obtained;[31Nap5 is formed in 12%
yield.
Properties and stability: The Nap, solutions prepared in
this way are golden orange, extremely sensitive to oxidation, and stable for 7-10 days in concentrations of
M
at room temperature. These solutions are considerably
more stable than the solutions of coronand-free Lip5 in
THF.['] Upon further concentration, Nap, undergoes rearrangement, in particular with formation of Na2Pl6 and
1.0
t
0.4
E
0.5
t O.:
E
0.2
[*I
[*'I
280
0
Prof. Dr. M. Baudler, S . Akpapoglou, D. Ouzounis,
Prof. Dr. F. Wasgestian, B. Meinigke
Institut fur Anorganische Chemie der Universitat
Greinstrasse 6, D-5000 Koln 41 (FRG)
Prof. Dr. H. Budzikiewicz, H. Miinster
lnstitut fur Organische Chemie der Universitat
Greinstrasse 4, D-5000 Koln 41 (FRG)
Contributions to the Chemistry of Phosphorus, Part 185. This work was
supported by the Deutsche Forschungsgemeinschaft and the Fonds der
Chemischen 1ndustrie.-Part 184: M. Baudler, J . Simon, Chem. Em.. in
press.
0 VCH Verlagsgesellschati mbH, 0-6940 Weinheim. 1988
350
LOO
650
Xlnml-
0.1
0
Xhml
-
Fig. I. Electronic spectrum of Nap,/[ IS]crown-6/THF solutions: concentra
tion of NapS ca. 3 x lo-' M (a) and
M (b).
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Angew. Chem. Int. Ed. Engl. 27 (1988) No. 2
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