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Controlled Modification of Crystal Habit by УTailor-MadeФ Impurities Application to Benzamide.

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or aryl group (Route I). If the 5-position bears only hydrogen atoms then tert-butyl N-(2-hydroxyethyl)imidates 3
are formed (Route 11). The reactions always proceed selectively in only one direction, irrespective of the type of substituents at the 2-position. Table 1 lists some examples.
Table I . Reaction of 2-oxazolines 1 in the system KOrBu/HMPT [a]. n
in the case of l i . n =2. Ferr=ferrocenyl.
+ff-NH-C
I;
I
2
11-0
1
point of view, far superior than any of the previously reported methods.
3
R'
R2
R3
f
[h]
Product
Yield
Received: March 24, 1982 [ Z 171 IE]
German version: Angew. Chem. 94 (1982) 650
The complete manuscript of this communication appears in:
Angew. Chem. Suppl. 1982, 1440- 1448
[%I lbl
la
lb
lc
Id
le
If
Ig
lh
li
lj
lk
II
Im
In
lo
CH3
H
CHI
CH3
(CH,),C
H
(CHI)IC
CH3
ChHS
H
ChHr
H
CeHr
CH3
o - H ~ N C ~ HH
~
p-C6H4
H
Ferr.
H
Ferr.
CHI
H
CH3
(CHI)~C
H
H
C,H5
Ferr.
H
CHI
CH3
CH,
CH,
CHI
CeH5
CH3
CH3
CH,
CH3
CHI
H
H
H
H
16
18
18
18
1.3 [el
1.5 [fl
18
17
7 [el
16
4
18
18
18
I96
2a [dl
Zb
2c [d]
2d
2e [dl
2f [d]
2g
2h Id)
2i [dl
2j [d]
2k
3a
3b
3c
3d
lcl
I cl
25
30
76
70
86
67
90
70
83
[Cl
34
50
28
[a] Molar ratio KOfBu : 1 = 5 : I ; 80 "C. [b] The isolated products gave correct
elemental analyses and spectroscopic data. [c] Not isolated; same boiling
point as HMPT, soluble in water. Characterization by 'H-NMR in HMF'T.
[d] Mixture of the Z- and E-form; 2-fraction 70-75%. [el 110°C. [fl
100 "C.
The rate of reaction strongly depends on the temperature and on the molar ratio KOtBu : 1. Thus, e.9.. reaction
of l e in the system KOtBuIHMPT at 100 "C with a molar
ratio KOtBu : le of 5 : 1 proceeds quantitatively only after
about 2 h, at 140°C even after 2 min. A molar ratio of
KOtBu : 1 = 5 : 1 is recommended for syntheses on a preparative scale. A sudden drop in the rate of reaction is observed at molar ratios of less than 2 :1. At a molar ratio of
1.5 : 1 quantitative conversion requires 5 h. With equimolar
amounts of KOtBu and 1 the reaction is even slower,
and the vinylamide 2 formed as intermediate reacts further to give a byproduct; e. g. l e reacts at 110 "C to give 4e
(22% yield).
@CH-'%-CH=CH-CH3
0 c/H3
J
H=CRZR31
KOrBu/HMFT
Cpd.
L
la-k
4e
According to current interpretations of the reaction
mechanism the products 2 and 3 are formed as shown
(B =~Bu).
This novel method can be exploited for the preparation
of variously substituted N-vinylamides in satisfactory to
good yields from 2-oxazolines, which in turn are readily
Because of its broad
accessible via numerous
spectrum of use this new method is, from a preparative
Angew. Chem. Inf. Ed. Engl. 21 (1982) No. 8
CAS Registry numbers:
l a , 6159-22-4; l b , 4195-89-5; lc, 82495-87-2; Id, 82495-88-3: l e , 23437-027; If, 22020-69-5; l g , 33561-48-7; l h , 82495-89-4; l i , 53720-68-6; lj, 8251169-1; Ik, 82511-70-4; 11, 1120-64-5; l m , 30393-80-7; In, 7127-19-7; lo,
82511-68-0; (E)-2a, 5202-80-2; (Z)-Za, 5202-79-9; 2b, 5202-82-4; (E)-2c,
69775-44-6; (2)-Ze, 69775-43-5; 2d, 82495-90-7; (E)-2e, 5202-76-6; (Z)-2e,
5500-46-9; (E)-2f, 78007-47-3; (Z)-Zf, 5202-77-7; Zg, 5202-81-3; (E)-Zb,
82495-91-8; (Z)-2h, 82495-92-9; (E. E)-2i, 82495-93-0; (Z, Z)-Zi,82495-94-1;
(E, Z)-2i, 82495-95-2; (E)-2j, 82511-65-7; (Z)-2j, 8251 1-66-8; Zk, 8251 1-67-9;
3n, 82495-96-3; 3b, 82495-91-4; 3c, 82495-98-5; 36, 82511-64-6; 4e, 8249599-6
121 G. Schmitt, P. KJein, W. Ebertz, J. Organomet. Chem.. in press.
141 J. A. Frump, Chem. Reu. 71 (1971) 483.
Controlled Modification of Crystal Habit by
"Tailor-Made" Impurities: Application to
Benzamide**
By Ziva Berkovitch- Yellin, Lia Addadi, Marian Idelson.
Mein Lahav, and LesEie Leiserowitz
Minute amounts of impurities (or additives) present in
solution during crystallization may have a pronounced effect on the crystallization process, in particular on the morphology of the deposited crystals[*]. We previously reported changes in habit of amino acids and derivatives induced during crystallization by the presence of minute
amounts of chiral impurities of similar structure to the sub~trate[~-'!Through these changes a stereochemical correla[*I Dr. 2. Berkovitch-Yellin, Dr. L. Addadi, M. Idelson, Prof. Dr. M. Lahav,
[**I
Prof. Dr. L. Leiserowitz
Department of Structural Chemistry
The Weizmann Institute of Science
Rehovot, 76 100 (Israel)
This work was supported by the Stiftung Volkswagenwerk. We thank
Prof. M. D. Cohen for discussions.
0 Verlag Chemie G m b H , 6940 Weinheim. 1982
0.770-0833/82/0808-0631 $ 02.50/0
63 1
tion was established between the molecular structure of the
impurity, the crystal structure of the substrate, and the effected growth directions, leading to a proposal of a twostep mechanism for the binding of the impurity at the
growing crystal faces and retardation of growth. We have
found that slightly modified substrate molecules yield impurities which are particularly effective in inducing such
morphological changes.
By application of these principles it becomes possible to
grow crystals with desired morphologies by “tailoring” impurities which bind at a preselected face and thus inhibit
growth in a predictable manner. An advantage of this
method is that the effect of factors such as temperature,
solvent, and supersaturation may be kept constant by performing all crystallization experiments under identical
conditions, except for the nature and concentration of the
impurity. This approach is illustrated here for benzamide.
U
ysis indicates that only 0.2-0.5% impurities are found in
the bulk of the crystal, even when the amount in solution
was as high as 10%.
Received: March 24, 1982 [Z 163 IE]
German version: Angew. Chem. 94 (1982) 640
The complete version of this communication appears in:
Angew. Chem. Suppl. 1982. 1336-1345
CAS Registry number:
Benzamide, 55-21-0.
[2] P. Hartman in D. Fox, M. M. Labes, A. Weisberger: Physics and Chemistry of the Organic Solid State, by Interscience, New York 1963, Vol. 1, p.
369 and Vol. 2, p. 873; P. Hartman: Crystal Growth. North-Holland, Amsterdam 1973, p. 367.
141 L. Addadi, 2. Berkovitch-Yellin, E. Gati, N. Domb, M. Lahav, L. Leiserowitz, Nature 296 (1982) 21.
[S] Z. Berkovitch-Yellin, L. Addadi, M. Idelson, L. Leiserowitz, M. Lahav,
Nature 296 ( 1982) 27.
161 L. Addadi, 2. Berkovitch-Yellin, 1. Weissbuch, M. Lahav, L. Leiserowitz,
S. Weinstein, J. Am. Chem. SOC.104 (1982) 2075.
[7] L. Addadi, S. Weinstein, E. Gati, I. Weissbuch, M. Lahav, J. Am. Chem.
Sor. 104 (1982), in press.
LiI2Si,: Theoretical Interest Aroused
b
By Joel F. Liebman* and James S . Vincent*
Von Schnering et a[. recently reported”’ the remarkable
crystal structure of LilzSi7,a compound containing planar
Si, star clusters and planar Si5 rings. For our description of
these two inherent structures we present here alternatives
and precedents based on qualitative and quantitative MO
considerations or on comparisons with isoelectronic species.
We start with the Si, stars, which contain singly coordinated terminal silicon atoms, as found in HNSi and
H,CSiL3];they can be formulated as Si,* (A).
This anion is “n-isoelectronic” with the Y-aromatic(61
carbonate ion Coif, i. e. both ions have the same number
of n-electrons and atoms. Because of the smaller charge,
Siz- should be more stable than the Si:- species postulated by von Schnering et al.‘]’.
C
d
Fig. 1. Crystals of benzamide grown in absence and in presence of increasing
amounts of impurities: a) pure benzamide, b) with benzoic acid (3%, 5%.
loo%),c) with o-toluamide (I%, 5%, to%), d ) with p-toluamide (3%, 5%,
10%).
Benzamide crystallizes from ethanol in plate-like crystals elongated along the b-direction (Fig. la). The general
features of this morphology may be rationalized in terms
of the packing characteristics.
In the light of the correlation between the crystal structure and morphology of benzamide, it was possible to
choose impurities to specifically modify the relative rates
of growth along the three principal directions: Retardation
of growth primarily along the b-axis was achieved by adding benzoic acid. This induces the crystals to grow in rodform extending along the a-direction (Fig. 1b). Retardation
of growth along the a axis was achieved by adding 1- 10%
of o-toluamide to the mother solution. This induces the
crystals to grow in the form of rods extending along the bdirection (Fig. lc). Finally, as expected, thinner and thinner platelets (Fig. Id) were obtained by adding increasing
amounts of p-toluamide.
In all cases the habit was modified gradually with the
concentration of impurity in solution (Fig. 1). HPLC anal632
0 Verlag Chemie GrnbH, 6940 Weinheim. 1982
A
Also, because of the high charge, the existence of the
postulated Si:- and S i y - anionsI’l is not very likely.
In our opinion the Sig rings should be formulated as
Si:- ions; such species are n-isoelectronic with the wellknown cyclopentadienide ion. The possible presence of the
2 n Si;’ species has also been considered. From symmetry
considerations and mathematical operations, as well as
consideration of the crystal structure, we deduced that lithium is present as Li+ and Li: in Li12Si71’01.
We therefore
suggest that Li12Si7 be formulated as Li24Si14 =
(Li + ) g ( ~ i : ) 5 ( ~ i ~ - > ( ~ i ~ - ) 2 .
Received: June 12, 1981,
revised: June 8, 1982 [Z 165 IE]
German version: Angew. Chem. 94 (1982) 649
The complete manuscript of this communication appears in:
Angew. Chern. Suppl. 1982, 1424-1428
[“I Prof. Dr. J. F. Liebman, Prof. Dr. J.
S. Vincent
Department o f Chemistry, University of Maryland
Baltimore County, Catonsville, M D 21 228 (USA)
0570-0833/82/0808-0632 $! 02.50/0
Angew. Chem. h i . Ed. Engl. 21 (1982) No. 8
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crystals, habits, уtailor, application, controller, benzamide, modification, impurities, made
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