冠醚合成

ring are given in Table 1.
Of note are (C12-013(C5-C6-07-
the values for the polyether
On one side the bridge is attached
orthogonal
Cl-C2) to the ring while on the other side the bridge and ring are nearly coplanar C8). Significant differences also appear
data indicate
is
the a lack of
approximately
symmetry
t-g-t-g-g-t,
although
OlO-Cl1 is 90".
The angle between
planes formed by the two aromatic between the aromatic
ቤተ መጻሕፍቲ ባይዱ
of 2 (n=l)
to TiClk-Zn
gave the desired
compound,
,J, (n=l) (83%
as a mixture
of r- and L-isomers from cyclohexane,
by IH NMR).
The E-isomer
separated
by recrystallization7 Compound
from this mixture of the E-A parameters
methods.'* analysis13, is shown in
The structure Fig. 1. Structural
(n=l),
bridge.
by X-ray diffraction
for the macrocyclic
OF STILBENE
CROWNS.'
JulianTirado-Rives,
Richard David Gandour*, and Frank Rolf Fronczek Department of Chemistry Louisiana State University 70803 Baton Rouge, LA
in the bridging procedures,
of the aldehyde.
simple experimental an attractive
of separation interesting
of r- and L-isomers
make this approach
entry into some potentially
in the bond angles about the two aryl ether oxygens, bridge about
07 and 013.
The conformation
along the polyether the dihedral
(07-CS-Cg-OlO-Cll-C12-013)
b. Vogtle,
M. P.; Kees, K. L.; Krepski,
the aromatic
rings are restricted by linking
from rotating
are desired.
be readily
accomplished
the 2,2' positions for polyether
with an appropriate and for cycloThis letter crown and E-
Recent advances
in synthetic
methods
podands2
have suggested
a straightforward syntheses
approach
to the desired molecules.
the facile two-step
of a mixture
of double bond isomers of stilbene
compounds. into the chemistry of the isomers of 1 and syntheses of analogs are
Investigations currently
in progress. The authors wish to express for his continuing interest their gratitude and helpful to their colleague Prof.
gave the desired
1639
1640
(n=2) in
43% yield
as a mixture
of r- and L-isomers by chromatographic determined
(48/52:r/z
by 'H NMR).
The E-isomer11
was separated
No appreciable
signals were to inter-
the temperature
from 300 to 200 K, indicating
that the barrier
among the rotamers
is lower than 10 kcal/mole. in the 'H NMR spectra in r-4 of L-J (n=1,2). The vinylic A possible
*&A
0
“x
x=Br, n=l x=OTs, n=2 Compound phenoxy)-ethyl] 4
(n=l)
ether, $
was made in 60% overall yield from salicylaldehyde via bis[2-(2-formyl(n=l). Salicylaldehyde was treated with sodium hydroxide in dioxane:
(n=1,2)
viz.,
CHO
E- and Z-[a,e]-dibenzo-7,10,13-trioxacyclotrideca-1,3,5-triene
and Z-[a.e]-dibenzo-7,10,13,16-tetraoxacyclohexadeca-1,3,5-triene.
+
OH
Ti Cl4 Zn
Acknowledgement George
R. Newkome
suggestions.
References
and Notes GM 29128-01.
This work is supported by a grant from the National Institute of Health, J.T.-R. acknowledges the CONACYT of Mexico for financial support. a. Vogtle, F.; Weber, E. Angew. F .; Heimann, U. Chem. Ber., McMurry, J. E.; Fleming, 3255-3266. Chem. Int. Ed. Engl., @_Z, Is, 753-776;
in the crystal
was not observed
C2 symmetry
in the molecule.
l6
Since the only way to explain in solution
the NMR and X-ray data was by a rapid conformational rotamers (synchronous rotation
Salicylaldehyde of triethylene
was treated with sodium hydroxide to produce 2 compound ,&
by addition
glycol ditosylate
(n=2) in 72% yield!0
of 2 (n=2) to TiClt+-Zn in dioxane
by addition of bis(tbromoethy1) in dioxane6 (60/4O:E/z while ether to produce $
HMPA (2:1, V/V)4 followed yield.5 yield) Addition
(n=l)
in
73%
readily TLC.
rings is 22.8".
These structural
rings and a non-equivlence structure
of the vinylic protons. in the NMR ('H and 13C) both
This lack of symmetry spectra, which indicated
Tetrahedron Letters,Vol.23,No.l6,pp Printed in Great Britain
1639-1642,1982
0040-4039/82/161639-04$03.00/O 01982 Pergamon Press Ltd.
SYNTHESES
AND STRUCTURE
serves as a model for a crucial step in proposed I* without It is especially protection