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Olefins from -Hydroxycarboxylic AcidsЧSynthesis of Isomerically Pure - and -Asarone.

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Table I. Steric course of the reaction of 1 with 2 (tetrahydrofuran, 22"C, 5
min). Presumed mechanism: group I: E2; group 11: E2 and E l ; group 111:
El.
1
R*
R'
Group
3
Yield (bl
2 : E [a]
IC'
[I .S-H]
1
2c
a
b
C
d
e
f
14
15
Ph
Ph
Ph
tBu
OPh
OPh
Me
Et
iPr
nPr
>98
>98
>98
>98
>98
>98
Ph
Me
Et
tBu
Vinyl
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
2-Fury1
4-MeOCsHa
4-Me2NC6H4
Et
Et
:2
:2
73
82
92
60
85
84
I
94 : 6
85 : 15
73 : 27
55 : 45
2 4 : 76
< 2 :98
91
82
87
82
81
82
11
< 2 : 98
< 2 : 98
96
87
92
111
:2
:2
:2
:2
13
Received: March 30, 1983 [Z 328 IE]
German version: Angew. Chem. 95 (1983) 638
The complete version of this communication appears in:
Angew. Chem. Suppl. 1983. 851-859
CAS Registry numbers:
la, 75029-45-7; lb, 80339-91-9; Ic, 92969-50-4; lc', 66633-30-5; Zb, 8647150-3; 2c-H, 86471-51-4; 2c-D, 86471-52-5; n-Bu-3a-H, 66633-29-2; 1-Bu-3aH, 86471-53-6; n-Bu-3a-D, 75349-86-9; r-Bu-3a-D, 86471-54-7; k - H , 8647155-8; n-Bu-4a-H, 86471-56-9; t-Bu-4a-H, 16240-44-1; n-Bu-4a-D, 86471-570; f-Bu-4a-D, 86471-58-1; &-H,86471-59-2; 9, 86471-60-5; 12, 86471-61-6;
13-H, 86471-62-7; 13-D, 86471-63-8; 14-H, 86471-64-9; 14-D, 86471-65-0;
15-H, 1076-69-3; 15-D, 86471-66-1; n-BuLi, 109-72-8;t-BuLi, 594-19-4; PTD,
4233-33-4.
131 H. Meier, T. Echter, Angew. Chem. 94 (1982) 68; Angew. Chem. Int. Ed.
Engl. 21 (1982) 67; Angew. Chem. Suppl 1982. 91.
[4] J. Zountsas, H. Meier, Liebigs Ann. Chem. 1982, 1366.
161 Presumably 9 is identical to the compound CS6Hl6
obtained in the Bamford-Stevens reaction of the sodium salt of 2,3-homotropontosylhydrazone"], although the spectroscopic data only conform to a moderate extent.
171 M. Oda, Y. Ito, Y. Kitahara, Tetrahedron Left. 1975, 2587.
[lo] B. MauzC., J. Organornet. Chem. 131 (1977) 321, and references cited
therein.
,"
i
i
Ir
m
n
0
p
Fk
< 2 :98
[a] a-m: Determined by GC; D-p: determined by 'H-NMR (60 MHz,
CDC13).
Aside from 3, ca. 10%B-lactone is also formed from la-d,
b-
m.
pared to R2, R' is of minor significance and merely shows
an influence on the acids in group 11. The erythro acids
4a--c, h-m (notation analogous to 1, see Table I) always
afford >98% ( E ) - 3 in yields of 80-95%, independent of
the nature of R' and R2.
Olef ins from B-Hyd roxycarboxylic AcidsSynthesis of Isomerically Pure a- and $-Asarone **
By Johann Mulzer* and Ortrud Lammer
The dehydrative decarboxylation of o-hydroxycarboxylic acids (1, 4) with the adduct 2 has proven useful for
the synthesis of ole fin^'^^^. We report here on the steric
course of the reaction, and, as an application, we describe
the synthesis of isomerically pure a- and $-asarone (11
and 13, respectively).
1E 2
(2)- 3
1 lfhreol
(€1 - 3
OH
L
R'
L lerythroi
ln the threo series@](Table 1) the isomeric distribution
shifts with increasing M effect of R2 from pure (2)-3 to
pure (E)-3. The residue R2 can be catagorized into three
groups. I: RZ with small + M effect. In these cases pure
(> 98%) ( 3 - 3 is formed. 11: RZ with medium M effect.
(Z)and ( a - 3 are both formed in varying amounts. 111: RZ
with large + M effect. Up to > 98% (E) is obtained. Com-
+
+
[*] Prof. Dr. J. Mulzer, 0. Lammer
[**I
628
Institut fiir Organische Chemie der Universitat
Universit2tsstrasse 1, D-4000 Diisseldorf 1 (Germany)
This work was supported by the Deutsche Forschungsgemeinschaft and
the Fonds der Chemischen Industrie.
0 Verlag Chemie GmbH, 6940 Weinheim, 1983
I
o*c'o,
H
IZi - 3
COEt
1
/El - 3
0-P-N,
Phj E
!
Scheme I. E=C02Et.
-EtO2C-NH-NH-C02Et
58
5A
7
These results find a mechanistic rationalization in the
hydroxy-activated intermediates 5 (from 1) and 7 (from
4), which decompose via E2- or El-fragmentation, depending on the electron suppIy from RZ(Scheme I). In the
threo series these two mechanisms lead to stencally different products. The E2-reaction is coupled with the anti-conformation 5A and furnishes (9-3.The El-route, on the
other hand, proceeds via the conformer 5B,sterically favored by the larger R'-R2 distance, and 6 to (a-3.
Thus,
the data in Table 1 can be interpreted to the effect that
group I is operated by the E2-mechanism and group 111 by
the El-mechanism. In group 11, on the other hand, both
mechanisms depend on the position of equilibrium
5A + 5B ; the E 1 -decomposition being favored more and
more with increasing bulkiness of R' (h-m). In the erythro
series the all-anti arrangement 7 is the optimal intermediate for both mechanism; hence, (E)-3 becomes the sole
possible isomer.
Synthesis of a- andp-asarone I I andI3, respectively: Asarone 13, a constituent of calamus oil, was first recognized in
1977 as a novel chemosterilizing insecticide["'. The activity
0570-0833/83/0808-0628 $ 02.50/0
Angew. Chem. Inr. Ed. Engl. 22 (1983) No. 8
is connected with the (Z)-geometry["]. 11 and 13 cannot
be prepared in isomerically pure form by Wittig reaction['*], and they are almost unseparable even by TLC.
clobutenone framework, utilizing photocycloaddition as a
key step.
0
0
OH
1
R = Me
10 lthreo
erythro =1 1 1
11 l > 9 8 % )
OH
fhreo
- 12
13 ( >98 % I
Scheme 2. Ar= 2,4,5-trimethylphenyI.
As an easy access to 11 and 13 we chose the reaction of
10 and 12 with 2 (Scheme 2). The electron-rich aryl group
(R') in 10 enforces the El elimination and, quite consistently, 11 is formed from 10 in >98% yield. In the case of
12, on the other hand, the methyl group induces an E2mechanism; up to >98% of 13 is isolated. The transition
from 10 to 12 corresponds to an interchange of substituents R' and R2 with largely differing + M effects. The
character of elimination is-in complete agreement with
our interpretation-thereby completely shifted from El to
Irradiation of 6-cyano-1,3-dimethyluracil,2, and excess
ketene diethyl acetal in acetonitrile at - 25 "C using a highpressure mercury lamp (Pyrex filter) gave cycloadduct 3
(40%) and rearranged product 4 (23%). The formation of
rearranged adducts such as 4 has previously been shown
Conto occur in the photoaddition of 2 to other 01efind~~.
version of 3 into 5 (80%) was readily accomplished by
reaction with potassium t-butoxide in dirnethylformamide.
Treatment of acetal 5 with 90% trifluoroacetic acid (TFA)
gave cyclobutenone 1 (77%) [m. p. = 108 - 110°C; 'HNMR (CDCl3): 6=3.38 (s, 3H), 3.40 (s, 3H), 3.67 ( s ,
2 H)1.
0
AN
0
CN
By Isao Saito*, Fuyuhiko Kubota, Koji Shimozono, and
Teruo Matsuura+
Dedicated to Professor G. 0. Schenck on the occasion
of his 70th birthday
The synthesis of highly photochemically reactive pyrirnidine bases is of special importance for photochemical
modification of nucleic acids"]. Upon irradiation, pyrimidine bases possessing cyclobutenone frameworks are expected to exhibit high reactivity toward nucleophiles, since
photochemical ring-opening of cyclobutenone may produce highly reactive vinylketene derivatives"]. We describe
here the synthesis of 2,4-diazabicyclo[4.2.0]oct-1(6)-en3,5,8-trione 1, the first uracil derivative possessing a cy['I Prof. Dr. I. Saito, F. Kubota, K. Shimozono, Prof. Dr. T. Matsuura
Department of Synthetic Chemistry, Faculty of Engineering
Kyoto University, Kyoto 606 (Japan)
Angew. Chem. Int. Ed. Engl. 22 (1983) No. 8
hu
0
Received: 18, 1983 [Z 350 IE]
German version: Angew. Chem. 95 (1983) 629
The complete version of this communication appears in:
Angew. Chem. Suppl. 1983, 887-897
Photocycloaddition of 6-Cyanouracil to Ketene
Diethyl Acetal: Synthesis of a Uracil Derivative
Possessing a Cyclobutenone Framework
CH2
EtOKOEt
Me
2
E2.
[7bI J. Mulzer, A. Pointner, A. Chucholowski, G. Briintrup, J . Chem. SOC.
Chem. Commun. 1979, 52.
[8] (Abstraa) The use of threo-eryrhro descriptors for p-hydroxycarbonyl
compounds is contradictory to the original convention derived from
threose and erythrose. However, since more recent alternative descriptors do likewise not offer an ideal solution to the problem we stay by
fhreo-ezyrhro and-despite all reservations-define these configurations
according to C. H. Heathcock, C. T. White, J. J. Mimson, D. VanDerveer, J . Org. Chem. 46 (1981) 1296.
[ I l l B. P. Saxena, 0.Koul, K. Tikku, C. K. Atal, Nature 270 (1977) 512.
1121 Chem. Eng. News 1979, April 16, p. 24.
+
0
Me C N O E t
3
4
F A
tBuOK
3 & 70
N
Me
5
OEt
OEt
1
0
0
6
7
Cyclobutenone 1 is stable at ambient temperature in
the usual organic solvents, including alcohols; however, irradiation of methanolic solutions of 1 resulted in rapid
formation of 6 (55%) and 7 (21%). 7 also formed by prolonged irradiation of 6, whereas the latter probably originates from the trapping of vinylketene 8 by methanol.
11
9, R = t B u
10, R
= SH-CHI
CO&e
a
Unexpectedly, cyclobutenone 1 reacts smoothly with
primary amines without irradiation at ambient temperature
to give 5-substituted uracil derivatives in high yields. For
example, treatment of 1 with t-butylamine gave 9 quantitatively. When a solution of 1 and tryptophan methyl ester
0 Verlag Chemie GmbH, 6940 Weinheim, 1983
0570-0833/83/0808-0629 $02.50/0
629
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hydroxycarboxylic, asarone, olefin, isomerically, acidsчsynthesis, pure
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