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Diastereospecific GasSolid Additions with Cholesterol Derivatives.

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refineable butddiene ligands, enantiomeric molecules at equivalent lattice
sites.-4: satin-red, trigonal platelets; monoclinic, P2Jc (No. 14);
a=859.4(1), b=2745.4(4), c=855.5(1) pm, B= 117.73(1)"; V=1787x lo6
FOO0=984;CAD4
pm', 2 = 4 , M , = 5 0 2 . 5 ; T=24"C;p,,, = 1.868 g
(Enraf-Nonius), graphite monochromator, A= 0.7107 A (Ma,,), measuring range: 2"e6525", r(max)=60 s, h(- 10/10), k(0/32), I ( - 10/10);
6368 measured reflections, 161 resolved, 31 12 independent reflections,
2903 with 1>0.50(1) used for the refinement; solution of structure by
Patterson methods; 190 parameters, full matrix least squares refinement;
all non-hydrogen atoms anisotropic, H atoms calculated at ideal positions and incorporated in the structure factor calculation, numerical absorption correction, p =71.9 cm- I, six faces, crystals dimensions
0.42 x 0.05 x 0.42 cm3, transmission factors 0.1975 to 0.7425;
R = C(I1 Fol - IF, II)/C IFoI= 0.023; R, =[Zw(iFoI - lFcl)2/Z~F,2]"2
=0.023;
GOF=[Xw(l FOi- I
NO - NV)1"2 = 2.639
( w = 1/u2[FO]); AeO/
A'=0.87; shift/err=O.OO.
[8] Review: H. Yasuda, A. Nakamura, Angew. Chem. 99 (1987) 745; Angew.
Chem I n f . Ed. Engl. 26 (1987) 723.-Electronic factors do not suffice for
the observed conformational stability.
191 J. Wolf, H. Werner, Organometallics 6 (1987) 1164, and references cited
therein.
Diastereospecific Gas/Solid Additions with
Cholesterol Derivatives**
By Gerd Kaupp* and Christine Seep
Gadsolid additions are very simple, mild, and economical procedures. They often allow the selective synthesis of
highly reactive compounds ;['I however, pronounced stereoselectivities have only seldom been observed.",Z1 We
have now found that cholesterol and some of its esters exhibit gadsolid reactivity and undergo diastereospecific additions even as crystalline powders.
Owing to its cholesteric liquid-crystalline phase, cholesteryl oleate 1 has found wide appli~ation.'~'
When crystalline 1 (II) is allowed to react at -30 to -20°C for 10 h
with gaseous hydrogen bromide in excess, the HBr adds
regio- and diastereospecifically to give 2 (loo%, m.p. 58+0.7, CcBr=669 cm-I), without the crystal
59"C,
melting.
Crystalline cholesteryl acetate 3, reacts more slowly
with gaseous HBr (1 bar, -3O"C, 6 d). The known 5abromide 4[41(loo%, [a]&'=+2.3, CcBr=669 cm-') is obtained regio- and diastereospecifically. These reactions are
very easy to carry out. In solution (e.g., dichloromethane),
both reactions yield, in addition to 2 and 4, respectively,
an appreciable amount of side products, even if every attempt is made to exclude water.
____.
~
-
[*] Prof. Dr. G. Kaupp, C. Seep
[**I
Fachbereich Chemie - Organische Chemie I - der Universitat
Postfach 2503, D-2900 Oldenburg (FRG)
This work was supported by the Deutsche Forschungsgemeinschaft and
the Fonds der Chemischen Industrie.
Angew. Chem. Int. Ed. Engl. 27(1988) No. 11
Surprisingly, the gases HCI and HI (1 bar, -30 to
+25"C) do not react at all with 1, or 3,-apart from
changes in the color of the crystal to pale yellow or to reddish brown-and cholesteryl stearate is not even attacked
by the especially effective HBr. These findings show that,
instead of the reaction enthalpies, specific crystal effects
are presumably the crucial criterion in determining the
gadsolid reactivity. This is even true when the gases can
penetrate into the crystal, as shown by the change in color
without chemical reaction."'
The gadsolid addition of bromine to cholesterol 5 (1 : 1
ratio of the reactants, 25"C, 2 h) also proceeds quantitatively and diastereospecifically to give the thermodynamically less favored 5a,6B-dibromide 6af4.61([a]&'==
- 52,
CcB,=566, 591, 616 cm-'). Thus, without stabilization by
acetic acid of crystallization, this compound is now accessible in a form that can be stored for weeks at room temperature. It is a welcome starting material for mild and
economical gadsolid reactions with reactive gases such as
NH3, CH3NH2,HI, and CH3SH."]
The reaction of chlorine gas with 5 , (1 : 1 to 2 : 1, <0.2
bar, -5O"C, 5 h) exhibits little regioselectivity but is diastereospecific with respect to the proportion of addition at
the 5,6-positions, which maintains the steroid framework.
Thus, only the 5a,6fbdichloride 6br4Ican be isolated (after
preparative thin layer chromatography: 34%, [a]$n
= - 32,
Cccl = 656 cm-').['] At higher temperatures (above
- 30"C), the reaction becomes appreciably slower owing
to partial melting, since this protects the crystal from further contact with the gas. In this case, the gadsolid technique appears to offer little advantage over conventional
chlorination.
The configurations of the products 2, 4, 6a, and 6b are
supported['] by the optical rotations (see Ref. [4] and refer-
ences cited therein) and by characteristic CCl(CBr) vibra"1
tional frequen~ies.'~,
The products 2, 4, and 6,easily and economically obtained by the gadsolid technique under mild conditions, are
interesting intermediates for further reactions in solution.
0 VCH Verlagsgesellschaft mbH. 0.6940 Weinheim. 1988
0570-0833/88/1111-lfil]$ 02.50/0
I51 1
Experimental Procedure
Commercially available 5 (Aldrich or Fluka) contains water of crystallization
torr,
( ' H NMR detection) and is purified by sublimation in vacuo ( 5 x
bath temperature 140°C). The X-ray powder diagrams before and after sublimation are nearly identical. However, the FT-IR difference spectra show
weak new bands in the fingerprint region ( V = 1262, 1100, 1027, and 806
c m - ' ) for the sublimed cholesterol. The cholesteryl esters 1 (m.p. 44.5OC)
valand 3 (m.p. 116.5"C) (Aldrich) did not require further purification. [a]&"
ues in CHCI,; IR spectra in KBr.
A 500-mL round-bottom flask containing 1.0-3.Og of powdered 1, 3, or 5
was evacuated ( 5 x
torr). At the temperature given in the text, the gas
was passed through a vacuum line fitted with a pressure relief valve or the
reaction vessel was connected via a vacuum line with a reservoir containing
the calculated amount of gas, the reaction assembly being protected from
sunlight. After the required reaction time, the excess gas was pumped off.
The crystals were mixed and a representative sample was taken for ' H NMR
analysis. The finely crystalline products can be reacted further without initial
purification. They can be recrystallized from CH,OH o r CCla.
Received: May 24, 1988 [Z2774 IE]
German version: Angew. Chem. 100 (1988) 1568
CAS Registry numbers:
I , 303-43-5; 2, 117021-04-2; 3, 604-35-3; 4, 1857-88-5; 5, 57-88-5; 6a, 185780-3; 6b, 1857-79-0.
[I] G. Kaupp, D. Matthies, Chem. Ber. 119 (1986) 2387; ibid. I20 (1987)
1897; review: Mol. Cryst. Liq. Crysl. 161 (1988) 119.
121 P. C. Chenchaiah, H. L. Holland, B. Munoz, M. F. Richardson, J Chem.
Soc. Perkin Trans. 2 1986, 1775.
[3] See, for example, L. M. Blinov: Electro-Optical and Magneto-Optical
Properlies of Liquid Crystals. Wiley, New York 1983; H. Kelker, R.
Hatz: Handbook of Liquid Crystals. Verlag Chemie, Weinheim 1980.
[4] C. W. Shoppee, M. E. H. Howden, R. Lack, J. Chem. Soc. 1960. 4874.
[5] This is shown even more clearly when 5 , is treated with gaseous HCI (at
-20 to +25"C, yellow-green, later brown-orange) or HI (at -20 to
+25"C, beige, later red-brown; after pumping off the gas, colorless;
after exposure t o air, initially dark green, then anthracite-colored). In
neither case does a chemical reaction take place ('H NMR in CDCI,).
[6] In syntheses carried out in solution, this isomer has to be protected from
mutarotation to the 5B,6a isomer by crystallization with 1 mole equivalent of acetic acid: Org. Synth. Collect. Yo/. 4 (1965) 195 (cf. D H. R.
Barton, E. Miller, J . Am. Chem. Soc. 72 (1950) 1066). The optical rotation in [4]is given as [ a ] b = -44. In solution the value slowly decreases
owing to mutarotation.
171 These reagents, available as gases, react in the usual manner with crystals of 6a.
[8] Further 5,6-dichlorides of 5 cannot be detected, even before chromatographic purification, although the 5a,6a isomer is known to be stable
(no mutarotation) IS. P. J. Maas, J. G. De Heus, Recl. Truu. Chim. PuysBas 77 (1958) 531; [lo]] and, in the case of the dibromide, the 50,6a form
is more stable than 6a. In the reactions competing with 5,6-addition, the
steroid framework undergoes rearrangement according to the ' H NMR
spectrum. The exact constitution of the rearrangement products, however, could not yet be determined.
191 Further data supporting the constitution and purity were provided by
elemental analyses, mass spectroscopy, and 'H NMR spectroscopy at
high field strengths (300 MHz).
[lo] D. H. R. Barton, J. E. Page, C. W. Shoppee, J . Chem. SOC.1956, 331.
of [MCl,(PPh,),] (M = Co, Ni) with PhP(SiMe,), affords
the clusters 1-3 in very high yields.
The clusters contain Co4-tetrahedra or distorted cubic
Ni,-polyhedra whose faces are capped by PPh ligands."]
The analogous reaction of [CoCI2(PPh3),] with
P h A ~ ( s i M e ~on
) ~the
, other hand, leads to formation o f the
complex [C~,(p~-As)~(p~,q~-As,)(PPh~)~]
4, via a redox
reaction in which all As-C bonds of PhAs(SiMe,), are
cleaved.121
We have now investigated the reaction of [NiCI,(PPh,),]
with P h A ~ ( s i M e[Eq.
~ ) ~(a)]. A rapid dissolution of the normally sparingly soluble [NiCI,(PPh,),] is observed in T H F ;
a crystalline mixture of various clusters and small amounts
of metallic nickel separate out from the brown solution.[31
Crystals of 5 and 6 (yield: 50% referred to Ni) are obtained on treatment of the precipitate with 1,2-C2H4CI2
and subsequent covering of the solution with hexane.
Derivatives of 5 are obtained in an analogous way from
[NiC1,(PR3),] (R = C2H5, C,H,,). The IR spectra of 5 and
6 are almost identical with the spectrum of [NiCI2(PPh3),]
above V=400 cm-', and the recording of NMR spectra is
problematic owing to the sparing solubility and paramagnetic behavior of 5 . According to crystal structure analyses
5 and 6 contain the same cluster
However, an
accurate determination of the structure of 6 is not possible
because of a disorder of the PPh, ligands and the co-crystallizing C2H,CI, molecules. 5 (Fig. 1) contains a cubic Nig
cluster (Nil-Ni8), with a further Ni atom (Ni9) located in
its center. The distances between the Ni atoms of the cube
a Cubic Body-centered Ni9-Cluster**
By Dieter Fenske,* Kurt Merzweiler, and Johannes Ohmer
Dedicated to Professor Ernst Otto Fischer on the occasion
of his 70th birthday
Phosphane complexes of electron-rich transition-metal
halides react with E(SiMe,), (E = S, Se, Te) and
RP(SiMe3)2 (R = Ph, Me, Et) with formation of Me,SiCl
and mixtures of metal-rich clusters. For example, reaction
I*] Prof. Dr. D. Fenske, Dr.
K. Merzweiler, Dr. J. Ohmer
Institut fur Anorganische Chemie der Universitat
Niederurseler Hang, D-6000 Frankfurt am Main 50 (FRG)
[**I This work was supported by the Deutsche Forschungsgemeinschaft and
the Fonds der Chemischen Industrie.
15 12
0 VCH Verlag.sge.sellschajimbH. 0-6940 Weinheim. 1988
ci 2
Fig. 1 Molecular structure of 5 (without phenyl groups) in the crystal. Important bond lengths [pm] and angles ["I (+0.1"): Ni-Ni (in the Nig cube)
276.9-284.6(5), Ni-Ni9 238.2-248.4(6), Ni( 1+As
229.8-235.0(5), Ni9-As
261.0-264.1(6), Ni-CI 216.5-218.1(7), Ni-P 217.7-222.9(9): Ni-Ni-Ni (in the
Nis cube) 87.0-92.4, Ni-Ni9-Ni 69.8-71.2, 108.6-1 10.2, 178.4-179.7, Ni-As-Ni
72.6-75.1, 115.9-1 19.1, Ni(l-S)-As-Ni9 57.0-59.6.
0570-0833/88/1111-1512 $ 02.50/0
Angew. Chem. Int. Ed. Engl. 27(1988) No. I 1
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cholesterol, gassolid, diastereospecific, additional, derivatives
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