الفهرس 
Chapter I : IntroductionOnly 14 pages are availabe for public view
 |  | from | 174 |  |  |
| | | from | 174 | | |
Abstract
g]chromen-7-ylidene)benzenamine (5b), and the second minor
product was 4,9-dimethoxy-5-methyl-7H-furo[3,2-g]chromen-7-one
(8b). Compound 8b was obtained by partial hydrolysis of 5b
(Scheme 1).
O O CH3
R
OCH3 O
1a, R= H
b, R = OCH3
KOH
H2O O
R
OCH3 C
OH
CH3
O
2a, R= H
b, R = OCH3
Ph3P C C N Ph
3
in THF, at room temp.
O
R
OCH3 C
O
CH3
O
4a, R= H
b, R = OCH3
C
N Ph
HC PPh3 - Ph3P = O
O O N
R
OCH3
5a, R= H
b, R = OCH3
CH3
Ph
+
O O O
OCH3
OCH3
CH3
Scheme 1
8b
The reaction of (2-oxovinylidene)triphenylphosphorane (6) with 2a
and 2b was also investigated, to give (triphenyl-5-phosphanylidene)
acetic acid-5-acetyl-4-methoxy-benzofuran-6-ylester (7a) and
(triphenyl-5-phosphanylidene)aceticacid-5-acetyl-4,7-dimethoxybenzofuran-
6-yl ester (7b), respectively. When the phosphoranes 7a
and 7b are boiled in toluene, intramolecular Wittig reaction occurs
with the formation of 4-methoxy-5-methyl-7H-furo[3,2-g]chromen-7-
one (8a) and 4,9-dimeth-oxy-5-methyl-7H-furo[3,2-g]chromen-7-one
(8b) respectively, together with TPPO. The reaction of the stabilized
phosphonium ylide carbmethoxymethylenetriphenylphosphorane (9)
with compounds 2a and 2b, affords the chromenones 8a and 8b
respectively. In this case the stabilized phosphonium ylide 9 reacts
with the acetyl carbonyl group rather than the OH group to give the
Summary of part 1
IV
intermediates 10a and 10b which are lactonized to give compounds
8a and 8b with elimination of methanol (Scheme 2).
Ph3P C C O
6
in THF, at room temp. O
R
OCH3 C
O
CH3
O
7a, R= H
b, R = OCH3
C
O
HC PPh3
- Ph3P = O
Toluene
O O O
R
OCH3
8a, R= H
b, R = OCH3
CH3
C
H
C OCH3
O
Ph3P
9
in toluene
O
R
OCH3 C
OH
CH3
CH
10a, R= H
b, R = OCH3
C O
OCH3
Scheme 2
2a,b
- CH3OH
In addition the reaction of the phosphacumulenes 3 and 6 with 1-(6-
hydroxy-4-methoxybenzofuran-5-yl)-3-phenylprop-2-en-1-one (11a)
and 1-(6-hydroxy-4,7-dimethoxybenzofuran-5-yl)-3-phenylprop-2-
en-1-one (11b) was studied, too. The corresponding chromenes 13a-d
were obtained together with TPPO. Formation of compounds 13a-d
can be explained by the addition of the phenolic OH group of 11a,b
to the phosphacumulenes 3 and 6 to give first the phosphonium ylides
12a-d which then cyclized to the chromenes 13a-d.
The reaction of the oximes 14a and 14b with the phosphacumulenes 3
and 6 was performed to give the isoxazoles 15a and 15b. In this case,
cyclization occurred with the formation of the isoxazole ring and no
reaction was observed between compounds 14a and 14b and the
phosphorus reagents 3 and 6. In this senses the phosphacumulene
Summary of part 1
V
ylides 3 and 6 acts as Lewis bases that facilitate the dehydration process
(Scheme 3).
O
R
OCH3 C
OH
CH3
O
2a, R= H
b, R = OCH3
benzaldehyde
NaOH
O
R
OCH3 C
OH
C
O
11a, R= H
b, R = OCH3
C Ph Ph3P C C X
3, X = N- Ph
6, X = O
O
R
OCH3 C
O
HC
O
12a-d
C
X
HC PPh3
HC
Ph
O O X
R
OCH3
C C Ph
13a, R = H; X = N- Ph
b, R = OCH3; X = N- Ph
c, R = H; X = O
d, R = OCH3; X = O
NH2OH, HCl
O
R
OCH3 C
OH
CH3
NOH
14a, R= H
b, R = OCH3
Ph3P C C X
3, X = N- Ph
6, X = O
O
R
OCH3
15a, R= H
b, R = OCH3
O
N
CH3
Scheme 3
H H
H H
+ Ph3P = O
The reaction of 7-hydroxy-5-methoxy-2-methyl-4-oxo-4H-chromene-
6-carbaldehyde (16) with the phosphacumulenes 3 and 6 was also
investigated. Compound 16 was prepared by oxidation of the chromenone
1a with K2Cr2O7 and H2SO4. Treatment of the chromene carbaldehyde
16 with the phosphoranes 3 or 6 leads to the formation of
5-methoxy-2-methyl-8-phenylimino-8H-pyrano[3,2-g]chromen-4-one
(18a) and 5-methoxy-8-methylpyrano[3,2-g]chromen-2,6-dione (18b)
Summary of part 1
VI
respectively, along with TPPO. Compounds 18a and 18b are formed
through intramolecular cyclization of the intermediates 17.
The reaction of 7-hydroxy-5-methoxy-2-methyl-6-[(phenylimino)-
methyl] 4H-chromen-4-one (19) with the phosphacumulene 3
afforded the chromenone 18a together with N-phenyliminotriphenylphosphorane
(21). However when chromenone 19 was allowed to react
with phosphacumulene 6, the ester 20b was exclusively obtained.
Cyclization of 20b afforded 5-methoxy-8-methyl-pyrano[3,2-
g]chromene-2,6-dione (18b) and the phosphinimine 21. It is evident
that formation of compounds 18a and 18b involves the intermediates
20a and 20b which is spontaneously lactonize only in case of 20a
(Scheme 4).
O O CH3
OCH3 O
1a
K2Cr2O7
H2SO4
HO O CH3
OCH3 O
16
HC
O
Ph3P C C X
3, X = NPh
6, X = O
O O CH3
OCH3 O HC
O
C
X
Ph3P CH
17
X O O CH3
OCH O 3
18a, X = N- Ph
b, X = O
NaOH
aniline hydrochloride
HO O CH3
OCH3 O
19
HC
Ph N
Ph3P C C X
3, X = N- Ph
6, X = O
O O CH3
OCH3 O HC
N
C
X
Ph3P CH
20a, X = N- Ph
b, X = O
Ph
Ph3P N Ph
Scheme 4
21
- Ph3P=O
-
+
Summary of part 1
VII
The reaction of the phosphacumulenes 3 and 6 with 4-methoxy-5-
oxo-5H-furo[3,2-g]chromene-6-carbaldehyde (22a) and 4,9-dimethoxy-
5-oxo-5H-furo[3,2-g]chromene-6-carbaldehyde (22b) was
performed. Compounds 2a and 2b are used for the synthesis of the
carbaldehydes 22a and 22b directly via Vielsmeier-Haack reaction.
The reaction of the chromene carbaldehyde 22a with the phosphorane
3, resulted in the formation of the cyclobutylidene 25a. While the reaction
of compound 22b with 3 gave the cyclobutylidene 25b and the
phosphanylidene-cyclobutylidene (26). This reaction proceeds via a
[2+2]-cycloaddition of the carbonyl group in 22a and 22b to the ylidic
C-P bond of the phosphorane 3 to give the oxaphosphetane 23.
Elimination of TPPO from 23 leads to the formation of the unstable
ketene 24, which dimerizes to give 25a and 25b. However in case of
the reaction of the chromene carbaldehyde 22b with the phosphorane
3, the dimer 25b was isolated together with the cyclobutylidene
chromenone 26, which is formed by addition of 3 to the ketene 24
(Scheme 5).
Summary of part 1
VIII
O
R
OCH3 C
OH
CH3
O
2a, R= H
b, R = OCH3
O O
R
OCH3 O
22a, R= H
b, R = OCH3
CH
O
23
O O
R
OCH3 O
CH
O C C N Ph
Ph3
P
O O
R
OCH3 O
HC C C
O O
R
OCH3 O
C
H
Ph N
N Ph
C
H
O
O
R
OCH3
O
24
25a, R = H
b, R = OCH3
+
O O
OCH3
OCH3 HC
N
PPh3
N
Ph
Ph
26
Ph3P C C N Ph
3
POCl3
DMF
O
Scheme 5
N Ph
- Ph3P = O
The reactions of the carbaldehydes 22a and 22b with the phosphacumulene
6 was performed and yield compounds 27a and 27b
respectively (Scheme 6).
O O
R
OCH3 O
CH
O
O
27a, R = H
b, R = OCH3
Ph3P C C O
6
Scheme 6
22a,b
PPh3
The structure of the new products was assigned according to consistent
analytical and spectroscopic data (IR, 1H-, 13C-, 31P- NMR and
MS).