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Enantiomerism and Diastereoisomerism of Bishelical Bilatriene Dimers in the Crystal Lattice.

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specifically formed trans-stilbene structural unit could be isolated. The analogous reaction with phosphanes ( 1 6) and
( I c)[lbl likewise led stereospecifically to the phosphane oxides
(26) and ( 2 c ) , respectively. The products (2a)-(2c)
by formal addition of HzO could be characterized on the
basis of their spectroscopic data['].
(a), R,
R'= H ;
R' = H;
R,R'=- 9 - p h
Compounds ( 1 a)-(I c) remained completely stable in hot
anhydrous ethanol and could be recrystallized "normally".
Hence, the added HZOmust have originated from the commercial ethanol. The reaction was found to take place also in
other water-containing solvents, e. g . acetone/HzO. On using
aprotic solvents (e.g. acetone) and DzO the deuterated transolefins were formed.
The course of the reaction is discussed in more detail for
bis(phenylethyny1)phosphane (I b ) , since in this case a further
product (3) could be isolated which affords additional information on the mechanism of the reaction.
Fig. 1. Molecular structure of (3). For sake of clarity only the "added"
H atoms are shown. The standard deviations of the bond lengths (in pm)
are on average 0.5 pm [4].
and tolan structural units. Reduction of these phosphane
oxides (2) with SiHCI3['l leads to formation of novel transition
metal ligands with phosphane, acetylene, and olefin donor
sites within one molecule. Furthermore, the reaction route
B represents on of the few examplesL6]in which a phenyl
substituent is attacked nucleophilically by the leaving group
after apical ring-opening of a cyclic hydroxyphosphorane.
Exclusive attack of the phenylethynyl-substituted phenyl
ring in ( l b " ) might therefore be explained by formation of
a cyclohexadiene-allene system capable of conjugation.
Received: September 19, 1978 [Z 103 IE]
German version: Angew. Chem. 90, 1003 (1978)
CAS Registry numbers:
( l a ) , 58581-32-1 ; ( l b ) , 54100-67-3; ( I c ) , 68457-25-0; (2a), 68457-26-1;
(2b), 68457-27-2; (ZC), 68457-28-3; ( 3 ) , 68457-29-4; H20,7732-18-5
Intramolecular nucleophilic attack of the phosphorus at
a sterically favorable acetylene C-atomr31 in (I b ) leads to
the intermediate ( 1 b'), which can be stabilized in the presence
of H 2 0 as the hydroxyphosphorane (I b"). (I 6") decomposes
with cleavage of the apical P-COlefin bond to the intermediate
( I b"'), which on protonation of the carbanionic olefin C-atom
affords the stable end-product (2b) (route A). However, the
carbanionic olefin C-atom can also attack a benzene ring
nucleophilically leading to formation of the compound ( 3 )
containing a spiro-cyclohexadiene-allenestructural unit (route
B). In the presence of HCI only (26) is formed: apparently
the protonation of the carbanion C-atom proceeds more
rapidly than that of the nucleophilic addition to the benzene
ring. The unusual structure of ( 3 ) was confirmed by X-ray
The reaction ( I ) + (2) appears remarkable on two counts:
On simple "recrystallization", the o-phenylethynyl-substituted
triphenylphosphanes ( I a)-(I c ) can be transformed stereospecifically into triphenylphosphane oxides with trans-stilbene
[l] a) W Winter, Angew. Chem. 88, 260 (1976); Angew. Chem. Int. Ed.
Engl. 15, 241 (1976); b) synthesis of ( I b ) : W Winter, Chem. Ber. 109,
2405 (1976); synthesis of ( 1 c ) : analogous to ( I b).
[2] ( 2 a ) : yield 76 %,colorless crystals, m. p. 169-170°C (cyclohexane/benzene); IR: 1195 (P=O)and 960cm-' (C-H out-of-plane for trans-olefin);
'H-NMR (TMS, CDC13): olefin AB-system: JA= 7.83, Je=6.87,
J A B = 1 6 H z ; (26): yield 54%, colorless crystals, m.p. 16O-16l0C
(EtOH); IR: 2225 (-C=C-),
1190 (-0) and 96511-' (trans olefin);
'H-NMR (TMS, CDCl3): olefin AB-system: JA=7.80, &=6.83,
J A B =16Hz; (2c): yield 88 %, colorless crystals, m.p. 205-207°C
(EtOH); IR: 2210 ( - e C - ) ,
1190 (-0) and 950cm-' (trans-olefin;
'H-NMR (TMS, CDCI,): olefin AB-system: hA=7.62, de=6.38= 16Hz.
[3] D. W Allen, J . C. Tebby, Tetrahedron 23, 2795 (1967).
[4] Monoclinic, space group P2,/c; a=873.7(2), b=l817.4(10), 1639.8(5)pm,
!3= 104.16(2)";2=4; 2413 symmetry independent reflections [!>2rs(1)],
Nonius CAD-4, MoK,-graphite monochromator; determination of
phases by direct methods (SHELX); refinement: R=0.042 (P. 0, C
anisotropically, H isotropically).
[5] W Winter, unpublished results.
[6] S. E. Fishwick, J . Flint, W Hawes, S. Tripett, Chem. Commun. 1967,
11 13; S. E. Cremer, ibid. 1968, 1132; D. Hellwinkel, H.-J. Wiljinger,
Chem. Ber. 105, 3878 (1972).
Enantiomerism and Diastereoisomerism of Bishelical
Bilatriene Dimers in the Crystal Lattice
By Harald Lehner, Siloia E. Braslavsky, and Kurt Schaffner[*]
The all-Z-all-syn stereoisomers of bilatrienes are helical
in the crystal lattice"' 'I. In addition, appropriately structured
Dr. H. Lehner
Prof. Dr. S. E. Braslavsky, Prof. Dr. K. Schaffner [' '3
Institut fur Strahlenchemie im Max-Planck-lnstitut fur Kohlenforschung
Stiftstrasse 34-36, D-4330 Miilheim-Ruhr (Germany)
Permanent address: Institut fur Organische Chemie der Universitat,
Vienna (Austria).
[' '1 To whom correspondence should be addressed.
Angew. Chem. Int. Ed. Engl. 17 ( 1 9 7 8 ) N o . 12
molecules form bishelical dimers, by way of intermolecular
N-H ..' 0 bridges. If a helical bilatriene monomer possesses
C2 symmetry, i.e., if the substitution patterns of rings A
and D and of rings B and C are identical, dimerization
can lead to one such bishelical arrangement only; it has a
center of inversion and consequently it is achiral.
Structural data". 31 of the unsymmetrically substituted biliverdin dimethyl ester ( I ) reveal positional disorders of the
substituents which have not been satisfactorily explained as
yet. The single helices have no symmetry element in this
case (Cl). Instead, they are characterized by an orientation
as defined, e.g., b y the sequence of rings A+D, which for
the dimerization to bishelices now offersfour possible combinations, (M*)-(A), (P*)-(A), (B), and (C).
the relevance of our model considerations. A recent X-ray
analysis['] does in fact show a considerable disorder for the
ring A and D substituents. However, the homogeneity of
the crystal used had not been ascertained conclusivelyr6! A
single crystal X-ray analysis[3]of pure ( I )r4I has now revealed
a qualitatively similar disorder['].
The result could also arise from a crystal composed of
a 1 : 1 complex of (2) and (3). This possibility was unequivocally ruled out in an isotope dilution experiment. Equal
amounts of [D6]-(1)['] and (2) were dissolved in boiling
chloroform and then separated again by chromatographyf4].
The two products were indistinguishable from the corresponding starting materials by 270MHz 'H-NMR and mass spectra,
thus confirming the isomeric homogeneity of our X-ray sample.
The X-ray analytical disorder of the substituents of ( I )
can thus be rationalized in terms of head-to-head, head-to-tail,
and tail-to-tail dimerizations of the single helices occurring
with comparable probabilities, i. e. by the presence of several
diastereoisomeric and/or enantiomeric bishelical bilatriene
dimers. A similar situation has possibly been encountered
in the case of bilirubin with ridge-tile conformation[*].
Received: September 15, 1978 [ Z 107 IE]
German version: Angew. Chem. 90, 1012 (1978)
CAS Registry numbers:
( I ) , 26615-10-1; (2), 26458-42-4; ( 3 ) . 26458-43-5
(B) and (C) are achiral, and they are diastereoisomeric with
respect to each other and to the enantiomers (M*)-(A) and
(P*)-(A)r5]. If the substituents d o not strongly perturb the
C2 symmetry of the bilatriene skeleton, the three bishelical
aggregates (A), (B), and (C) will differ only slightly in energy,
and they can be expected therefore to coexist with comparable
probabilities in the crystal lattice. It is now evident that,
whenever more than one of these three bishelical arrangements
occur simultaneously, positional disorders of the substituents
will be simulated and thus impede the interpretation of X-ray
i i
5 i
W S. Sheldrick, J. Chem. Soc., Perkin Trans. 11 1976, 1457.
J . !-!Bonfglio, R. Bonnett, M . B. Hursthouse, K . M . A . Malik, S. C.
Naithuni, J. Chem. SOC. Chem. Commun. 1977, 829; G. Srruckmeier.
J . Engel, ibid. 1978, 33; W S. Sheldrick, A. Borkenstrin, J . Engel, G.
Struckmeirr, J. Chem. Res. (M) 1978, 1616, and references cited therein;
G. Struckmeier, U . Thewalr, J . - H . Fuhrhop, J. Am. Chem. SOC.98, 278
(1976); J . !l Bonfiglio, R . Bonnett, M . B. Hursthouse, K . M . A. Malik,
J. Chem. SOC.Chem. Commun. 1977, 83.
Unpublished results by S. Mohr, Y - H . Tsay, C. Kriiger, whom we thank
for helpful discussions and for communicating their crystal data of biliverdin dimethyl ester ( I ) [4]: space group PT, a=12.419(4). b=14.609(5),
c =9.790(2) A,ct = 11 1.82(2),/j= 90.69(2), :=97.38(2)", V= 1631.8 A', Z = 2.
R=0.1180 for 1938 observed reflections, 1 > 2 . 0 ~ ( 1 )Disorder
as in [l].
Refinement of two independent molecules in P1 (R=0.0880) did not
substantially change the disorder model.
S. E. Braslavsky, A . R. Holzwarth, H . Lehner, K . Schuffner, Helv. Chim.
Acta 61, 2219 (1978); H . Lehn@r, S. E. Braslauskg, K . Schajfner, Justus
Liebigs Ann. Chem. (1978). in press.
The stereochemical relationship of these four bishelices IS similar to
the cyclostereoisomerism of catenanes, with (M*)-(A) and (P*)-(A) corresponding t o cycloenantiomers and (B) and (C) t o cyclodiastereoisomers;
see R. Cruse in E. L. Eliel: "Stereochemie der Kohlenstoffverbindungen",
Verlag Chemie, Weinheim 1966, pp. 21 5 - 2 2 5 ; H . L. Frisch, E. Wasserman,
J. Am. Chem. Soc. 83, 3789 (1961).
We thank Dr. W S. Sheldrick for information on the preparation and
isolation procedure used for the X-ray sample (P. Kriiger, Ph. D. Thesis,
Technische Universitat, Braunschweig, 1976).
Compound [De]-(I) was obtained upon esterification of a mixture
of biliverdin isomers with C D 3 0 D / D 2 S 0 4and subsequent chromatographic separation of the esters [4]; m. p. 204-206°C; hexadeuteration
2 9 5 % by 270 MHz 'H-NMR and MS.
R . Bonnett, J . E. Dauies, M . B. Hursthouse, Nature 262. 326 (1976);
R. Bonnett, J . E. Davies, M . B. Hursthouse, G . M . Sheldrick, Proc. R. SOC.
London B202,249 (1978).
Dipotassium Hexaisobutyldialuminate, a Complex
Containing an AI-A1 Bond
By Heinz Hoberg and Siegjiiied Krause"]
The dehalogenation of diisobutylaluminum halides with
alkali metals can lead, under certain conditions, to the formation of tetraisobutyldialuminum['l.
This observation encouraged us to investigate the possibility
of isolating intermediates in the previously reported reaction
Biliverdin dimethyl ester (I ), with the substitution pattern
unsymmetrical only with respect to the methyl and vinyl
positions at rings A and D, fulfils the requirements for testing
Angew. Chem. Int. Ed. Engl. 17 (1978) N o . 12
[*] Priv.-Doz. Dr. H. Hoberg, Dr. S. Krause
Max-Planck-Institut fur Kohlenforschung
Postfach 01 1325, D-4330 Mulheim-Ruhr 1 (Germany)
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lattices, crystals, diastereoisomers, dimer, bishelical, enantiomerism, bilatriene
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