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Octopus Molecules.

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in which a silyl and an ally1 group migrate, can be regarded
as evidence in favor of an asymmetrical transition state. In
any case, the silyl group shift brings about a kind of Walden
inversion of the substituents attached to the stationary C
atom. This prediction is currently under investigation“!
Received: July 19, 1974 [Z 107 IE]
German version: Angew. Chem. 86, 899 (1974)
~
.-
[ I ] Dyotropic Rearrangements, Part 5.-Part 4 . M. 7 Rurrz, Angew. Chem.
86, 416 (1974); Angew. Chem. internat. Edit. 13, 402 (1974).
[2] M. T Rue(:, Angew. Chem. 84, 161 (1972): Angew. Chem. internat.
Edit. 11, 129 (1972).
[3] M. T. Rrrrz, Tetrahedron 29, 2189 (1973).
[4] Prepared by silylation of the corresponding (si1yl)methyl alcohols. The
structure was confirmed by spectroscopy and analysis.
[S] Methyl-I-naphthylphenylsilylgroup. Cf. L. H . Summer, C. L. F r w , G.
A. Purkrr. and K . W Michuel, J Amer. Chem. SOC.86, 3271 (1964).
[6] This investigation should also yield informationahout possible alternative
mechanisms (c,. y. oxygen ylide formation).
octopus M
O I W ~[* I*I ~
By Fritz Vogtle and Edwin Webed*]
Knowledge gained about “coronates”[”, catapinates, and cryptatesIz1 has induced us to synthesize acyclic but “manyarmed” polyether, complex-forming ligands of type ( l a ) , in
which each “arm” is fitted with numerous donor atoms. Here
we not only report about the unusual complexing tendency
of such ligands but also show how their conformational mobility is impeded by spatial crowding.
The hexasubstituted benzene derivative ( I a ) containing 18
oxygen atoms is obtained as a yellowish, viscous oil (6=4.
which is insoluble in water, on reaction of benzenehexakis(methanethiol) and 1-bromo-3,6,9-trioxatridecane (“1 -bromo-
R
$
R~
,R
Ill
121
I6 I
171
131
14 I
R
R
151
191
R
--A
S 0 0 OCLHQ
S-O-OCH?
SO2CH3
[*] Prof. Dr. F. Vogtle and DipL-Chern E. Weher
lnstitut fur Organische Chemie der Universitat
87 Wiirtburg, Am Hubland (Germany)
This work was supported by the Deutsche Forschungsgemeinschaft
and the Fonds der Chemischen Industrie.
[**I
814
triethyleneglycol o-butyl ether”). It is a remarkably powerful
complex ligand for cations since a solution of ( I a) in dichioromethane removes a great part of the picrate from ~ O - ‘ N
aqueous alkaline-earth picrate solutions (Mg”, Ca”, Sr’’,
B a Z + )and almost the entire salt from alkali-metal picrate
solutions (Li’, Na’, K’, Rb’, Cs’) from the aqueous into
the organic phase“!
This occurs faster and more completely than can be achieved
with known crown ethers‘s]; only cryptate ligands such as
“C2.2.21” and “[2.2.1]” are equally effective. The usual oligoethers, glycols, and comparative substances such as I-bromotriethyleneglycol o-butyl ether and triethyleneglycol butyl
ether have no such action under analogous conditions.
According to a study with space-filling models the unexpectedly strong complex formation by ( l a ) (which invites a
study of polyfunctional acyclic biomolecules) must be accompanied by considerable conformational changes. It shows
remarkable phenomenological parallelisms to the mode of
food capture by an octopus using its suction pads(’!
->
R
R
R
R
Picric acid itself can also be easily extracted from aqueous
solution by dichloromethane that contains an “octopus molecule” such as (1 a ) . Also remarkable is the, admittedly weak,
complexing of cobalt thiocyanate by ( l a ) and its partial
transfer into the dichloromethane phase. Heavy-metal salts
such as CuCI,, NiCl,, Ce(SO,),, Pr(NO,),, and Nd(NO,),
could not be extracted from water by dichloromethane solutions of ( I a ) or by crown ethers and ”I72.2.21” (under comparable conditions).
A distinct fall in complexing tendency occurs if the number
of donor positions is decreased, either by shortening of the
armsas in ( I b ) (colorless viscous oil; F =4.11) or by successive
diminution of their number. Among position isomers with
equal numbers of arms the I ,3,5-isomer ( 8 ) and, on presence
of only two substituents, the 1,2-disubstituted system (9) stand
out for powerful ligand properties. ( 8 a ) is certainly less efficient than ( I a ) having three more arms, but it is more effective
than ( 6 a ) and even than ( 4 a ) ; here steric factors (see below),
lipophilic character, and solubility properties of the ligand
seem to be importantc2’.
Complex-formation by the crystalline potential ligand (1 c)
(m.p. 262”C, dec.; 6=4.54, in pyridine) that contains six pyridine rings is hard to establish because of the sparing solubility.
The wafer-insolublepyridine derivatives (10) and ( I 1 ) (colorless viscous liquids; F = 3.97 and 3.85, respectively) have special
phase-transfer properties: although alkaline-earth- and alkalimetal picrates cannot be thereby extracted from aqueous solution, picric acid dissolved in water is rapidly and completely
transferred into the organic phase (dichloromethane). This
does not occur with comparable substances such as pyridine
under analogous conditions. Further, in methanol ( 1 0 ) forms
Angrw. Chem. internut. Edit. J Vul. 13 ( 1 9 7 4 ) J No. 12
a deep-green copper(1r)complex, but no interaction is observ-
able with other heavy-metal ions such as (20'- or Ni2*.
Oxygen-free hexasubstituted benzene derivatives f' 1 d - f ' I f ) ,
( I h)i7I as well as ( I g), ( 1 i), and the hexasulfone ( I k ) were
investigated for comparison and naturally have no complexligdnd properties.
The free ligand molecule ( I a ) gives an unexpected 'H-NMR
spectrum (Fig. f ) , from which conclusions can be drawn about
intramolecular mobility phenomena that are slow on the NMR
time scale: the signals of the c1- and y-methylene protons
are considerably broadened at room temperature. Increase
in temperature sharpens all the signals, cooling broadens them
further. Clearly there is steric overcrowding in the hexasubstituted system ( I )['I.
shorter chains, as is shown by the very marked broadening
of the signals of the 2-methylene protons.
Whereas ( I h ) shows a barely broadened benzyl singlet
(6=4.29) in spite of the six space-filling phenyl substituents,
the sulfone ( 1 k ) (m.p. > 350"C, dec; 6 = 5.13) exhibits somewhat broadened C H r signals even at room temperature.
Remarkablealso-is the finding that introduction ofsix sterically
demanding 2,6-dimethylphenyl groups as in ( 1 i ) (m.p. 248 to
251 " C ;6 = 3.76)i31does not notably increase the steric crowding over ( I h ) ; the 36 CHJ protons appear as a sharp singlet
[S(CH.3)=2.30 in CDCl3].
As the number of side chains decreases, the signal broadening
becomes less; the steric interactions presently appear to be
in the order ( l a ) > ( 2 u ) (6=3.59--4.18) > ( 3 a ) (6=4.02,
4.23) > ( 4 a ) (6 = 3.77, 3.92, 4.10) > ( S a ) (6 = 4.2); and
with ( 6 a ) (6 = 4.17, 3.98), ( 7 0 ) (6 = 3.98), (Na) (6 = 3.83), and
( 9 a ) (6 = 4.02) interaction is no longer unequivocally detectable. Replacing a benzene-hydrogen at m that is not contiguous to the interacting substituents, as in the change from
( 6 a ) to ( 4 a ) or from ( 7 u ) to ( 5 a ) , may increase the hindrance
to rotation, and this can be interpreted as a steric buttressing
effect" 'I.
i
(la)
-&
a-CH2
I
4
LO-CLHg
Y -CH2
I
A h
cl
OMS
I
2
2
4
al
I
2
Fig. I . 'H-NMR spectrum of ( l a ) al several temperatures. a ) and c ) in diphenyl ether, b) rn CDCI2: 6OMHz. OMS=octamelhylurclotetrasiiolanc
We wished to discover whether this steric effect (a) was a
characteristic of the polyoxa compounds ( I a) and ( I b ) for
which the heteroatoms or coiling of the arms would be responsible, or (b)was to be ascribed in general to steric overcrowding
in the persubstituted benzene ring; so we studied the proton
resonance of the hexaorganothio compounds (1 d)-( 1 i)
which contain substituent chains of different lengths and different branching, as well as the hexasulfone ( 1 k ) . It transpired
that here too broadening of the benzylic CH2 signals could
occur: whereas no steric hindrance of rotation could be
detected in ( I d ) (6=4.12) or in hexakis(bromomethy1)benzene['1(6=4.71 in CHBr3 at 158"C)[101by 'H-NMR spectroscopy, we found somewhat broadened signals of the E- and
y-methylene-protons already for n-butyl substitution (1s)
(' = 4.14). The longer
chains Of' particu1ar1y7'") (m.p.
38-39°C; 6=4.16) with their greater effective steric requirements, cause steric overcrowding that is greater than for the
Angrw. Chrm. intrrnat.
Edit. 1 Vol. 13 (1974) / No. 12
Received. July 30, 1974 [ Z I I I IE]
German version. Angew. Chem. 86. 896 (1974)
[ I ] Proposal for designation of crown ether complexes. P. Neiimarm and
F . Viigrir. unpublished.
[2] Reviews: C. J. Pedersen and H. K . Frmsdo$J Angew. Chem. 84, 16
(1972);Angew. Chem. internat. Edit. I / , 16(1972); J . M. Lehn. Struct. Bonding
16, 1 (1973); I;. Viigrle and P. Neumann, Chem -Ztg. 97, 600 (1973): D. J . Cram
and J . M . Cram, Science 183, 803 (1974): see also: D. S t . C Black and A J .
Hartshorn, Coord. Chem. Rev. 9,219 (1973).
[3J N M R signal (ppm) of the r-CH?-protons (in CIX'I, unless otherwise
stated).
[4] For method see C . J . Prdersm, J . Amer. Chem. Soc. Y2, 391 (1970).
[ S ] This is true also for the rnrra-bridged crown ethers descrlbed by us
[ F . Vogrlrand E. Weher.,Angew Chem. 86, 126 11974): Angcw. Chem. internal.
Edit. 13. I49 (197411.
[6] H. Wur-rnhuch Lehrbuch der Zoologre. Gustav Fischer Verlag, Sluttgart
1970...- ~~t~~~~ m o ~ e c u ~ e with
S
eight and ten arms may be synthesized
using naphthalene and biphenyl systems. respectively.
815
[7] H. J . BucLr~.Rcc. Trar. Chlm. Pays-Bas 54, 745, 905 (1935).
degenerate in the center (l00MHz; r=6.75ppm; Avl
1.8;
J = 9.0, 6.5, 2.5 Hz). In contrast, H6 and H8 in (7) are subject
to different anisotropic effects owing to the asymmetrically
arranged phenyl groups, and their resonances at T = 6.45-6.85ppm give rise to three broad absorptions (Avl ?=3.0,
4.5, and 3.0Hz). In all cases the sterically more favorable
euo-arrangement of the two five-membered rings is confirmed
by the symmetry properties of the non-superposed 'H-NMR
multiplets.
Characteristically structured UV-spectra (O/O transitions at
271 nm; E = 370, 400, 435) and fluorescence spectra (&, =
0.0049, 0.0086, 0.0049) serve for the detection of non-conjugated phenyl groups in ( 6 ) , ( 7 ) , and ( 8 ) , respectively.
The primary product ( 3 ) [h,,,=280 (sh, 8800); 304 (15000);
311 (15000); 327 (sh, 9300)] is obtained uniformly by irradiation (253.7 nm) of ( 6 ) and (7) at - 190°C[21.Correspondingly,
irradiation of ( 8 ) affords ( 9 ) . (6), (7), and ( 8 ) photolyze
without phosphorescencein the rate ratio 5.4: 1 : 1.1. In agreement with the two-step mechanism for the photocleavage
of four-membered rings[3.'I, there is no quantitative correlation between fluorescence intensity (see above) and photoreactivity. Thus it should not be expected that different benzylic
C-C bonds will be cleaved with the same probability, nor
that the resulting different diradicals'"'' will be stabilized
to reactant and product in the same proportion.
The isolation of (3)and ( 9 ) permitsa check on the mechanistic
considerations. Both fluoresce intensely (& = 0.66 and 0.69,
respectively; cyclohexane) and photoadd to undiluted cyclo-
[8] K. . W i h i i , Introduction to Stcreochemistr>. W. A. Bcnjamin. Inc., Neu
York 1966. H. A . Siuuh Einftihrung In die lhcorclische organische Chemie.
Verlag Chemle, Weinheim. 4th Edit. 1966: M . S. Mrnn1u~7-Steric Effects
in OrganicChemistr). Wile). New Y o r k 1956. Seealso: B Nilssoil, P. ,Wurtn.,on, K. o/.sson. and R. E. CUJVLT.
J. Amer. Chem. SOC. 96. 3190 (1974).
.
C'rystallogr. 18, 851 (1965).
[9] X-ray structure analysis: P. M u r ~ r Acta
[lo] P. Neumann, Dissertation, Unlversitat Heidelberg 1973.
[ I I ] M. Riryer and F-. ff. WrsiAermo..J. Amer. Chem. SOC. 72, 19 (1950):
U! Thrilucker. and R Hopp. Chem Ber. Y2, 2293 (1959): W Thri/ur.krr.
and H . Bdhm Angew. Chem. 7Y, 232 11967). Angeu. Chem. Internat. Edit.
6. 25 I (1967). Revieu. E L. Elirl, Stereochemistry of Carbon Compounds.
McGraw-Hill. New York 1962.
l,4-Diphenylbicyclo[2.2.0lhexanes from 1,2-Diphenylcyclobutenes[**]
By Gerd Kaupp, Christoph Kiichel, and Inge Ziminermann[*'
All previously reported [2x+ 2x1 photocycloadditions of
diphenylacetylene to isolated or conjugated double bonds
have led only to 1,2-diphenylcyclobutene derivatives or to
the valence isomers derivable from them"]. We now report
intermolecular consecutive additions and preparatively interesting quantum yields of the photosynthesis of I ,4-diphenylbicyclo[2.2.0]hexanes from 1,2-diphenylcyclobutenes.Because
of the longer lifetime of the fluorescent excited states and,
presumably, substantial chromophore leveling, the conditions
for such additions are much more favorable than in the case
of open-chain cis-stilbenes, which do not undergo photocycloadditions[".
( 5 5) H6''
+
0
5H6''
(8)
The photolysis of diphenyl acetylene (1 ) in cyclopentadiene
(2) (Pyrex filter, -30°C) leads-undoubtedly via ( 3 ) (m. p.
82-83"C)-to
(6) (m.p. 132.5--134"C)and (7) (m.p. 110°C)
in 32 % and 11 % yields, respectively[2! Other products formed
include ( 5 ) , which is formed in 10 (x yield uia the photo-DielsAlder adduct ( 4 ) I 3 ] ,some polymers, and alteration products
formed during the chromatographic separation.
On catalytic hydrogenation, (6) and ( 7 ) both afford (8)
(m.p. 113--114°C). They can, however, be readily distinguished by their 'H-NMR spectra : All conceivable
isomers of structure (6) possess a twofold axis of symmetry,
and the resonances H h / H i 2 give rise to a 7-line spectrum,
pentadiene (2) (h>315nm; -10°C) to give (6) and ( 7 )
(in the ratio 3 :
and probably e.~o,e.~o-1.7-diphenyltetracyclo[5.5.0.02~6.08~'z]dodeca-3-ene[i.e., (6) or (7) with one
hydrogenated double bond]. A preparative application consists in the corresponding reaction of ( l l ) [ " ' to give ( 1 2 )
(m.p. 77°C;yield: 59%)[']. The fluorescence intensities of ( 3 ) ,
( 9 ) ,and ( I I ) (also no phosphorescence at - 196°C) in cyclopentadienearereduced to 1/6,1/5, 1/10, respectively, compared
to those in cyclohexane.
[*] Doz. Dr. G. Kaupp and 1. Zimmermann
Chemisches Laboratorium der Universitit
78 Freiburg, Albertstrasse 21 (Germany)
Stud. Ref. C . Kiichel
Kant-Gymnasium
7858 Weil a. Rhein (Germany)
This work was supported by the Deutsche Forschungsgemetnschaft
and the Fonds der Chemischen Industrie.
[**I
816
The considerable UV quantum yieldsi3]for the consumption
of the cis-stilbene components ( 3 ) , ( 9 ) , and ( I Z ) ($=0.50,
0.44, and 0.57, respectively; 0-90 '%, reaction) underline the
Angew. Chrm. inttmaf. Edit.
1 Vol. 13 ( 1 9 7 4 ) N o .
12
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