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Carbon as Leaving GroupЧStereochemistry of nucleophilic Substitution.

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intensity, are identical with those observed for the complex
[((C5Me5)(CO),Fe}P(Cr(CO)5]=PAryl][9~
and the complex
[((C5Mes)C0)2Fe)As(Cr(C0)5)=PAryl],~'"1
thus indicating
a similar o-donor/n-acceptor relationship of the ligands
[((C5Me5)(CO)ZFe}E'=E2Aryl]
(El, E2 = P, As) toward the
Cr(CO)s group. In the mass spectra (EI) of 4 and 5 , the
peaks with the largest m / z value correspond to the molecular ions, whereas the molecular ion peak of 6 was not
observed under comparable conditions. In the FD mass
spectrum of 6, the molecular ion of 3 produces the peak of
greatest intensity. An additional signal at m/z=918 (37%)
is assigned to 5 . The facile fragmentation of 6 to 3 and 5
is possibly due to the very bulky substituents.
residue in 20 m L of ether afforded red-violet crystals of 4 at - 28°C (0.14 g,
lO%). 'H NMR: 6= 1.39 (s, 9H,p-tBu), 1.53 (s, 15H, C5Me5), 1.67 (5, ISH,
C5Me5),1.98 (s, 18H, o-tBu), 7.35 (s, 2H, aryl). "PI'HJ NMR (AB spectrum):
6 ~ = 6 . 4 ( P 1 ) 6n=40.6
,
(P2), J(AB)=227 Hz. IR (CO). 6=1994(m), 1988 (s),
1948 (s), 1945 (5) c m - ' . €1-MS: m/z 876 (Mo).
On concentration of the
mother liquor to ca. 15 mL, 0.07 g (5Oh)of 5, m.p. 157°C (dec.), was obtained.
' H N M R : 6 = 1 . 3 6 ( s , l8H,p-tBu), 1.58(s, 15H,C5Me5),1.65(s,36H,o-tBu),
7.26 (s, 4 H , aryl). "PI'H} NMR: 6=24.2 (s): IR (CO): C = 1992 (vs), 1980 (w),
1949 (vs), 1939 (w) c m - ' . ELMS: m / z 917 (M'). The green mother liquor
was concentrated to ca. 5 mL and allowed to stand overnight at -28°C.
thereby affording 0.54 g (27%) of dark green crystals of 6 , m.p. 133°C (dec.).
'H NMR: 6= 1.36 ( s , 18H, p-tBu), 2.10 (s, 18H, o-tBu), 7.36 (AB spectrum,
J A ~ = 2Hz, 2 H , aryl), 7.55 (AB spectrum, J A B = 2 Hz, 2H, aryl). "P{'HJ
NMR: 6=87.7 (s); IR (CO): 6 = 1983 (vs), 1947 ( s ) , 1931 (m) c m - ' . FD-MS:
m / z 598 ([(q5-C5Me5)(CO)zFe-P=As-Aryl]Q,100°/~).
7:After a reaction time of 5 min, the solution of 1 (3.14 g, 7.40 mmol) and 2
(2.90 g, 7.40 mmol) in T H F (50 mL) was treated with 80 mL of a photochem-
ically freshly prepared solution of [((Z)-CaH Ie)Cr(CO),](10.00 mmol) in hexane. After stirring for I h at 20°C. the reaction solution was evaporated to
dryness and the solid residue was chromatographed (Al20, Woelm TSC);
column, d = 5 cm, 1=25 cm). Elution with petroleum ether gave an orange
zone containing 0.05 g of 8 (2%). Subsequent elution with a mixture of petroleum ether and ether ( 5 : l ) gave a dark green zone, from which 1.36 g (3 l%)
of 6 could be isolated. A red fraction followed which contained 1.88 g (32%)
of red 7, m.p. 184°C (dec.). 'H NMR: 6= 1.38 ( s , 9 H , p-tBu), 1.47 (s, 15H.
C5Me5), 1.71 (s, ISH, o-rBu), 7.65 (s, 2 H , aryl). J'P('H/ NMR: 6=616.3 (s).
1R: 5=2061 (s), 1986 (w), 1946 (vs), 1938 (s), 1925 (5) [Cr(CO)], 2018 (s), 1973
(s) c m - ' [Fe(CO)]. El-MS: m / z 790 ( M O ) . - S : m.p. 173°C; ' H NMR:
6 = 1.34 (s, IS H,p-rBu), 1.50 (s, 36H, o-rBu), 7.64 ( s , 4 H , aryl). €1-MS: m/z
640 (M').
Received: May 31, 1988 [Z 2795 lE]
German version: Angew. Chem. 100 (1988) 1595
[A]
Fig. I . Molecular structure of 4 . Selected bond lengths
and angles ["I:
As-PI 2.316(1), As-P2 2.350(2), P b P 2 2.207(2), As-C 2.010(6), Fel-PI
2.373(2), Fe2-P2 2.326(2); PI-As-P2 56.5(1), As-PI-P2 62.5(1), As-P2-PI
61.0(1), PI-As-C 105.8(1), P2-As-C 104.5(2), As-PI-Fel 110.5(1), P2-PI-Fel
1 l7.l(l), As-P2-Fe2 124.6(1), PIbP2-Fe2 105.3(1).
The X-ray structure analysis of 4 is of particular importance['" since there is little available structural information
on molecules containing As-P
and such data are
fully lacking for As-P three-membered rings. The basic
framework of the molecule consists of an ASP, triangle in
which the As-P2 bond (2.350(2) A), with the substituents
in cis orientation, is slightly lengthened compared with the
As-PI bond (2.316(1) A). The P-P bond lengths
(2.207(2) A) correspond to the normal
As expected, the endocyclic angle at the As atom (56.5(1)") is
smaller than those at the phosphorus centers (61.0(1)' and
62.5(1)').
The [(~5-CsMes)(CO),Fe]groups on P1 and P2 are
oriented in a trans fashion. The steric bulk of the substituents on the ASP, framework results in markedly increased exocyclic bond angles at P1 (110.5", 117.1 ") and
P2 (1 24.6 105.3 ").
O,
Experimental procedure
NMR spectra recorded in COD6at 22°C; ' H NMR, 200 MHz; I R spectra
recorded in cyclopentane.
2 : A 2.5 M solution of n-butyllithium in hexane (23 mL) was added dropwise
to a solution of I-bromo-2,4,6-tri-tert-butylhenzene
(18.1 g, 55.6 mmol) in
T H F (250mL). After stirring for 1 h at -5O"C, the reaction mixture was
cooled to -70°C and treated dropwise with AsCI, (4.7 mL, 55.6 mmol). The
green reaction solution was evaporated to dryness (-30°C) and the residue
was dissolved in n-pentane (150 mL), the resulting solution filtered, and the
filtrate concentrated until the onset of crystallization. Colorless crystalline
needles formed at -28°C and were recrystallized from n-pentane. Yield
5.3g (24%) 2. ' H NMR: 6= 1-15 ( s , 9H,p-6Bu), 1.51 ( s , ISH, o-IBu), 7.44
(5, 2 H, aryl). El-MS: m / z 390 (M').
4 - 6 : A solution of 1 (1.40 g, 3.30 mmol) [7] in T H F (30 mL) at 0°C was
treated with 2 (1.29 g, 3.30 mmol), resulting in a spontaneous change in color
from red-brown to dark green. The reaction mixture was stirred for an additional 5 min at 20°C and then evaporated to dryness. The solution of the
I538
0 VCH Verlagsgesellschafl mbH. 0.6940 Wernherm, 1988
CAS Registry numbers:
1,9601-32-0;2, 117184-75-7; 3, 117184-70-0: 4, 117184-71-1; 5, 117184-72-2:
6 , 117184-73-3: 7, 117184-74-4; 8, 117184-76-6; [(z)-C,H,,]Cr(CO),, 9288973-1; (Z)-C,H,,, 931-87-3.
[I] Reviews: a) M. Baudler, Pure Appl. Chem. 52 (1980) 755; Angew. Chem.
94 (1982) 520; Angew. Clrem. Int. Ed. Engl. 21 (1982) 492; Z . Chem. 24
(1984) 352; b) H. W. Roesky, M. Witt, Reu. Inorg. Chem. 4 (1982) 45.
[2] a) M. Baudler, J. Hahn, H. Dietsch, G. Furstenberg, 2. Nuturjbrsch. 8 3 1
(1976) 1305; b) M. Baudler. B. Makowka, 2. Anorg Allg. Chem. 528
(1985) 7.
131 M. Baudler, S. Klautke, Z Naturfbrsch. 8 3 6 (1981) 527.
141 M. Baudler, D. Habermann, Angew. Chem. 91 (1979) 939: Angew. Chem.
In!. Ed. Engl. 18 (1979) 877.
[5] M. Baudler, P. Bachmann, Angew. Chem. 93 (1981) 112; Angew. Chem.
I n ! . Ed. Engl. 20 (1981) 123.
[61 A. H. Cowley, J. G. Lasch, N. C Norman, M. Pakulski, J. Am. Chem.
Soc. 105 (1983) 5506.
171 L. Weber, K. Reizig, R. Boese, Chem. Ber 118 (1985) 1193.
181 F.-W. Grevels, V. Skibbe, J. Chem. Soc. Chem. Commun. 1984, 681.
[9] L. Weher, G. Meine, R. Boese, D. Blaser, Chem. Ber. I 2 1 (1988) 853.
[lo] L. Weher, D. Bungardt, R. Boese, Chem. Ber. 121 (1988) 1535.
[ I l l 4 : monoclinic, Pn, a=11.182(1), b=16.134(2), c=13.017(l)A,
~=114.73(1)", V=2133.0(4)t\',Z=2,p,,,,,=1.365gcm-',
MoKnradiation, scan range 3" 5 2 8 1 55", 5042 unique reflections, 4854 observed
reflections (Fo24u(F,,)), 228 refined parameters. R=0.051, R,, =0.056,
n'- ' = u2(6))+ 0.00152. Fi.
[I21 a) L. Weber, D. Bungardt, R. Boese, D. Blaser, Chem. Ber. I21 (1988)
1033; b) M. Baudler, Y. Aktalay, T. Heinlein, K.-F. Tebbe, Z. Nururforsch. B37(1982) 299; c) W. S . Sheldrick, Actu Crystullogr. 4. Sect. 8 3 1
(1975) 1789.
1131 K.-F. Tebbe, Z . Anorg. Allg. Chem. 468 (1980) 202, and references cited
therein.
Carbon as Leaving GroupStereochemistry of Nueleophilic Substitution
By Wolfgang Kirmse* and Klaus Zander
Dedicated to Professor Giinther Snatzke on the occasion
of his 60th birthday
Grob's cationic fragmentation"] can be regarded as the
reverse of electrophilic addition to alkenes or-referred to
I*]
Prof. Dr. W Kirmse, Dr. K Zander
Fakultat fur Chemie der Universitat
Postfach 102148, D-4630 Bochum I (FRG)
0570-0833/88/1Ilf-1538 $ 02 50/0
Angew. Chem l i l t Ed Engl 27 11988) Nu I 1
C-3-as nucleophilic substitution. Whereas a n antiperiplanar arrangement of the C-X and C-2-C-3 bonds is known
to be a prerequisite for many fragmentations,"] the stereochemistry at C-3 has, to our knowledge, not yet been investigated. Frequently, the fragmentation is supported by donor substituents (NR2, OR) on C-3; it then leads to planar,
resonance-stabilized fragment ions (route a in Scheme 1).
Our studies are concerned with bicyclic educts whose fragmentation is promoted by the release of ring strain.
YO
13 12
+ -c-c-c-X
I
11
I
l
l
+ \/ c=c'/ +
Y-c-
(b)
I
x@
Scheme I
In the bicycl0[2.2.1]heptane[*-~]and bicyclo[3.l.l]heptane series,['] fragmentation takes place only with a peralkylated carbon atom as electrofugal group and with
endo(truns) position of X. Suitably labeled starting compounds for our studies were obtainable from the known
lactones I['] and 2"' by stepwise reductioncB1with LiAID,
(Scheme 2). The diazonium ions 5 and 6,(exo,endo mix-
tures, only the endo-diazonium ions fragmentL2-']) were
generated from the tosylhydrazones 3b/4b of the ketones
3a/4a, respectively, by irradiation in aqueous sodium hydroxide. The ring-opening product 7 (9% from 3b, 15%
from 4b) shows separate signals in its 'H-NMR spectrum
(400 MHz) for the diastereotopic methyl groups (6= 1.12
and l.13), the intensities of which give the amounts of 7a
and 7b, respectively. For the determination of the configuration, 7 was converted by epoxidation and base-induced
ring-closure into 8, whose methyl groups (6= 1.10 and
1.28) can be assigned by NOE measurements. 3b preferentially affords 7a, 4b preferentially 7b; both starting compounds chiefly react with inversion (Table 1).
The increased ring strain of the bicyclo[2.1. llhexane
skeleton facilitates fragmentations also with a secondary
carbon atom as electrofugal group.'91 Reduction of the racemic ketone 9r9.101
with fermenting yeast yielded the alcohols 10a (ee = 98%)["] and l l a (ee = 66%) in the ratio 1.2 : 1
(Scheme 3). Reoxidation of 10a and l l a afforded enantiomeric ketones; the (lR,4R,SR)-configuration was assigned to the dextrorotatory ketone 9a on the grounds of
its positive circular dichroism.['21Irradiations of the tosylhydrazone 9b in aqueous sodium hydroxide and solvolysis
of the brosylates 10b and l l b in acetone/water (3 :2,
llO"C, 18 h) furnished product mixtures from which the
ring-opening product 15 was separated ; its configuration
was determined by ring expansion (1. dibromocarbene; 2.
hydrogenation) to the known (+ )-(S)-17.[13'The configuration of the brosylate not only influences the yield of 15
go
2
3
5
a: X
= 0
b: X
=
NNHTs
= CD,
+X
hX
1
AN?
X = O
X = NNHTs
1
1
1
;:;
X =
1oc
X
''\-\I
I
\1
OH
OH
u
7b
OH
X = OBS
=
NF
llc
X
12
4
9 b'
(S)-15
13
14
16
(R)-15
1
L
8a
+
OH
Scheme 2.
Angen.. Chem In,. Ed. Engl. 27 (1988) No I 1
OH
17
ia
Hoi5
19
Scheme 3
0 VCH Verlagsgesellschaft mbH. 0-6940 Weinheim. 1988
0570-0833/88/1111-1539 $ 02.50/0
1539
Table I . Stereochemistry of the fragmentations.
Starting compound
Product
Inversion : Retention
3b
4b
9b
IOb
Ilb
7
7
15
15
15
81 : 19
75 : 25
88 : 12
93: 7
79 : 21
( l o b : 36%, l l b : 9%), but also its enantiomeric purity (Table I).”” A 1 : 1 mixture of the epimeric diazonium ions
(lOc, ent-llc) is expected from the tosylhydrazone 9b ; the
results (18% 15) lie between those for 10b and l l b . 15 is
always formed with pronounced inversion (Table 1).
The substitution reactions of the methylbicyclo[2.1. Ilhexane derivatives indicate the participation of
bridged (e.g. 12 and 14) and open carbocations (e.g. 13).l9l
The transformation 1 4 s 1 2 via 13 is probably the reason
for the (inefficient) fragmentation of l l b , despite the
“wrong” position of the OBs group. The ring-opening with
inversion to (S)-15 can be ascribed to the bridged ion (ncomplex) 12, whereas racemic 15 is formed from 16. Evidence for the occurrence of 16 is provided by the H-shift
16-18, which leads to the tertiary alcohol 19. The
amount of 19 formed in the fragmentation reactions is,
however, markedly smaller than in the direct generation of
16. That 12 can be formed directly from 10b but only indirectly (via 13) from l l b would explain the differences in
yield and enantiomeric purity of 15 from the two processes.
The ring opening 5/6- 7 can be formulated in an analogous way, whereby a 7-bridged norbornyl
is
formed instead of 12. The predominant but incomplete inversion indicates that the fragmentations investigated here
are limiting cases of nucleophilic substitution. Such borderline cases (e.g. solvolyses of secondary alkylsulfonates)
have been explained in terms of a competition between o r
“b1ending”of the mechanistic extremes (e.g. SNl/SN2).[l5]
In our opinion the observed stereoselectivity is best explained in terms of a competition of the fragmentation
routes (a) and (c) in Scheme 1.ll6l
Received. June 3, 1988 [2798 IE]
German version: Angew. Chem. 100 (1988) 1596
CAS Registry numbers:
3b, 117408-44-3; 4b, 117408-45-4; 7a, 117408-49-8; 7b, 117408-50-1: 8a,
117408.53-4: Sb, 117468-01-6; 9b, 117408-46-5: lob, 117408-47-6; Ylb,
f17408-48-7: (R)-15, 117408-52-3; (S)-15, 117408-51-2.
[ I ] Summary reviews: C. A. Grob, P. W. Schiess, Angew. Chem. 79 (1967) I ;
Angew. Chem. lnt. Ed. Engl. 6 (1967) 1 ; C. A. Grob, ibid. 81 (1969) 543
and 8 (1969) 535; K. B. Becker, C. A. Grob in S . Patai (Ed.): The Chemistry of Double-Bonded Functional Groups, Part 2, Wiley, New York
1977, Chapter 8.
[2] W. Hiickel, F. Nerdel, Justus Liebrgs Ann. Chem. 528 (1937) 57: W.
Hiickel, P. Rieckmann, ibid 625 (1959) 1 ; W. Hiickel, H. J. Kern, ibid.
728 (1969) 49.
[3] D. V. Banthorpe, D. G. Morris, C . A. Bunton, J. Chem. SOC.81971. 687.
141 W. Kirmse, G. Arend, Chem. Ber. 105 (1972) 2738: W. Kirmse, S .
Brandt, ibid. 117 (1984) 2510.
(51 H. Indyk, D. Whittaker, J. Chem. SOC Perkin Trans. 2 1974, 646.
161 R. M. Moriarty, C . C. Chien, T. B. Adams, J . Org. Chem. 44 (1979)
2206.
17) T. W. Gibson, W. F. Erman, J. Am. Chem. SOC.91 (1969) 4771.
181 In both cases the reduction led first to the diol. The C D 2 0 H group of
the diol from 1 could be selectively tosylated; renewed reduction of the
tosylate generated the methyl group. In tosylation experiments the diol
from 2 yielded the cyclic ether (2, CD2 instead of C = O ) , which was
cleaved reductively with LiAlD (OfBu),/BEt,; cf. H. C. Brown, S.
Krishnamurthy, J . Am. Chem. Sor. 94 (1972) 1750.
[9] W. Kirmse, K. H. Kampmann, V. Zellmer, Chem. Eer. 120(1987) 1301.
1540
0 VCH Verlagsgesellschafl mbH, D-6940 Weinheim, 1988
[lo] T. W. Gibson, W. F. Erman, J. Org. Chem. 37(1972) 1148; W. R. Rotb,
A. Friedrich, Tetrahedron Lett. 1969, 2607.
[ I I] The enantiomeric purity (ee) of the alcohols IOa, ]la, and 17 was determined by gas chromatography of their camphanates.
[I21 G. Snatzke, U. Wagner, unpublished.
[I31 K. Freudenberg, P. J. Todd, R. Seidler, Justus Liebigs Ann. Chem. 501
(1933) 199.
[I41 Review: W. Kirmse, Arc. Chem. Res. 19 (1986) 36.
[I51 Discussion and literature: J. March, Advanced Organic Chemistry. 3rd
Edit., Wiley, New York 1985, p. 265: G. W. Klumpp: Reaktivrtat in der
Organischen Chemie. Thieme, Stuttgart 1978. p. 443.
1161 We consider a participation of the completely concerted route (b) in
Scheme I as unlikely. The contribution of (b) should increase with increasing ring strain ( 9 6 )and with poorer leaving groups (10b/10c) and
should increase the stereoselectivity This was not observed.
Synthesis and Structure of
[cyclo-C3H4- S02Ph12TiIOCH(CH3)212,
a C-Titanated “a-Sulfonyl Carbanion”**
By Hans-Joachim Gais,* Jiirgen Vollhardt,
Hans J . Lindner, and Helmut Paulus
The titanation of heteroatom- or resonance-stabilized
“carbanions” is a valuable instrument for control of selectivity.“.” However, little is known on the structures[31of the
titanium compounds f ~ r r n e d . ~ ’Our
. ~ . ~investigations
~
on
the reactivity of titanated sulfones[2b1led us, therefore, to
investigate their structure.[51
Herein we report on the synthesis, crystal structure analysis, and characterization by NMR spectroscopy of the titanium compound 2, which was generated from (phenylsu1fonyl)cyclopropyllithium 1 and chlorotriisopropoxytitanium by Li-Ti exchange and crystallized from n-hexane.
Crystalline 2 is stable at room temperature if protected
from air and moisture.
1
L=4
2
According to the crystal structure analysis,1612 is a true
diorganotitanium compound containing two enantiomeric
(pheny1sulfonyl)cyclopropyl moieties and- displaying normal Ti-C distances (average value 2.177 A) and short TiOiPr bonds (average value 1.763 A) (Fig. 1). Noteworthy is
the observation that one 0 atom of each sulfonyl group is
coordinated to the Ti atom, thereby extending the coordination number of the metal atom to 6. Evidence for the
existence of the two 0-S-C-Ti chelate rings and thus for
[*] Prof. Dr. H.-J. Gais, Dipl.-Ing. J. Vollhardt
Institut fur Organische Chemie und Biochemie der Universitat
Albertstrasse 21, D-7800 Freiburg (FRG)
Prof. Dr. H. J. Lindner
lnstitut fur Organische Chemie der Technischen Hochschule
Petersenstrasse 22, D-6100 Darmstadt (FRG)
Dr. H. Paulus
Institut fur Physikalische Chemie der Technischen Hochschule
Petersenstrasse 21, D-6100 Darmstadt (FRG)
[**I
This work was supported by the Deutsche Forschungsgemeinschaft. We
thank Prof. Dr. G. Boche for communication of unpublished results.
0570-0833/88/1111-1540 $ 02.SWO
Angew. Chem. Int. Ed. Engl. 27 (1988) No. I 1
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