Use of 2-(methoxycarbonyl)phenyllead triacetate in lactone synthesis

Article abstract of DOI:10.1007/s11172-006-0462-1

Reactions of 2-(methoxycarbonyl)phenyllead triacetate with β-oxo lactones and phenols in the presence of pyridine afforded polycyclic lactones in good yields. A one-pot three-step synthesis without isolation of intermediate products was developed.

Full text of DOI:10.1007/s11172-006-0462-1

Russian Chemical Bulletin, International Edition, Vol. 55, No. 9, pp. 1612—1616, September, 2006
1612
Use of 2ꢀ(methoxycarbonyl)phenyllead triacetate
in lactone synthesis
B. A. Maryasin,a A. S. Shavyrin,b J.ꢀP. Finet,c and A. Yu. Fedorova
ꢀ
aN. I. Lobachevsky Nizhny Novgorod State University,
23 prosp. Gagarina, 603950 Nizhny Novgorod, Russian Federation.
Fax: +7 (831 2) 65 8592. Eꢀmail: afnn@rambler.ru
bG. A. Razuvaev Institute of Organometallic Chemistry, Russian Academy of Sciences,
49 ul. Tropinina, 603600 Nizhny Novgorod, Russian Federation.
Fax: +7 (831 2) 12 7497. Eꢀmail: andrew@imoc.sinn.ru
cLaboratory "Chemistry and Biology of Free Radicals",
UMRꢀCNRS 6517, University of AixꢀMarseille 1 and 3,
Saint Jérôme Department of Sciences, 13397 Marseille Cedex 20, France.*
Fax: +33 (049) 128 8758. Eꢀmail: jeanꢀpierre.finet@up.univꢀmrs.fr
Reactions of 2ꢀ(methoxycarbonyl)phenyllead triacetate with βꢀoxo lactones and phenols
in the presence of pyridine afforded polycyclic lactones in good yields. A oneꢀpot threeꢀstep
synthesis without isolation of intermediate products was developed.
Key words: lactones, isocoumarins, organolead compounds, arylboronic acids, αꢀarylation,
reductive crossꢀcoupling.
Aryllead triacetates are widely used as Cꢀ and Nꢀarylatꢀ
of 4ꢀhydroxycoumarins with 2ꢀbromobenzoic acid in the
presence of CuSO4 8 or with methyl salicylate in the presꢀ
ence of a base have been used. However, these methods
are ineffective for the synthesis of isocoumarins of the
type A from electronꢀenriched polymethoxycoumarins.
Interest in this class of compounds is due to unique
photoꢀ and electrooptical properties that could be exhibꢀ
ited by polymethoxyꢀ and/or polyhydroxyisocoumarins A
with a powerful closed πꢀsystem.9 In addition, tetracyclic
isostructural analogs of dilactone A (natural benzoꢀ
pyranoꢀ, benzofuranoꢀ, isoquinolinoꢀ, and indolocouꢀ
marins) show a broad spectrum of useful biological
properties such as antitumor,10 antiviral (including
antiꢀHIVꢀ1),11 antiinflammatory, and anticoagulating acꢀ
tivities;12 some of them are promising agents for treatꢀ
ment of neurodegenerative diseases, e.g., Alzheimer
disease.13
The synthesis of isocoumarins A with the use of
organolead reagents implies a sequence of three "oneꢀ
pot" steps (Scheme 2). Transmetalation between arylꢀ
boronic acid 1 and lead tetraacetate in the presence of
catalytic amounts of mercury diacetate gives 2ꢀ(methoxyꢀ
carbonyl)phenyllead triacetate (2).14 We failed to isolate
reagent 2 in the individual state and used it in subsequent
syntheses as solutions. Supposedly, Cꢀarylation of enolizꢀ
able substrates with participation of aryllead triacetates
proceeds through the formation of covalent intermediꢀ
ate 3,15 its decomposition to αꢀarylation product 4, and fiꢀ
ing reagents for organic compounds of various classes.1
One of the most striking examples of the efficiency of
such reagents is the highꢀyielding arylation of natural flaꢀ
vonoids and their analogs. A variety of the resulting flaꢀ
vone derivatives include isoflavones, isoflavonones,2
3ꢀhydroxyneoflavonoids,3 and 3ꢀarylꢀ4ꢀhydroxycoumaꢀ
rins (Scheme 1, pathway A).4 Later, we have found that
the use of polyfunctional aryllead triacetates containing
two electrophilic centers allows the cascade synthesis of
substituted benzopyranoꢀ5 and isoquinolinocoumarins6
(Scheme 1, pathways B and C), where three to four sucꢀ
cessive steps are carried out without isolation of intermeꢀ
diate products.
The goal of the present work was to develop a novel
cascade methodology for the creation of lactone systems
of the type A from enolizable substrates (e.g., those
having the 4ꢀhydroxycoumarin moiety) with the use
of arylating organolead reagents (see Scheme 1, pathꢀ
way D). Only a few studies7,8 have been devoted to the
synthesis of derivatives of the type A. For instance, these
compounds have been obtained by the Pechmann conꢀ
densation of 4ꢀhydroxycoumarins with ethyl 2ꢀoxoꢀ
cyclohexanecarboxylate followed by catalytic dehydrogeꢀ
nation of the cyclohexane ring.7 Alternatively, reactions
*UMRꢀCNRS 6517, Universités d´AixꢀMarseille 1 et 3, Faculté
des Sciences Saint Jérôme, 13397 Marseille Cedex 20, France.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1554—1557, September, 2006.
1066ꢀ5285/06/5509ꢀ1612 © 2006 Springer Science+Business Media, Inc.

Organoleadꢀassisted lactone synthesis
Russ.Chem.Bull., Int.Ed., Vol. 55, No. 9, September, 2006
1613
Scheme 1
nally the spontaneous transesterification with the enolized
oxo group, yielding annulation product 5.
3,5ꢀdimethoxyꢀ (10) and 3,4,5ꢀtrimethoxyphenols (11),
2ꢀnaphthol (12), and βꢀdiketone 13.
Scheme 2
Compound
R1
R2
R3
6, 14
7, 10, 15, 18
8, 16
H
H
H
OMe
OMe
H
OMe
H
The reactivity of reagent 2 was tested in reactions with
the following substrates: unsubstituted 4ꢀhydroxycoumarin
(6), its natural dimethoxy and trimethoxy analogs 7—9,
OMe
OMe
OMe
9, 11, 17, 19
OMe

1614
Russ.Chem.Bull., Int.Ed., Vol. 55, No. 9, September, 2006
Maryasin et al.
Scheme 3
Reactions of 4ꢀhydroxycoumarins 6—9 with lead reꢀ
agent 2 under classic conditions14 in the presence of pyriꢀ
dine (3 equivalents with respect to compound 2) gave
isocoumarins 14—17 in 45, 42, 30, and 56% yields, reꢀ
spectively. Earlier,5a,b,16 it has been demonstrated that
the nature of the base employed in the Cꢀarylation with
organolead reagents can largely affect the reaction kinetꢀ
ics and the yields of the arylation products. Presumably,1
covalent reaction intermediate 3 can contain one or two
molecules of the base or the complexing agent, the nature
of which substantially influences the topological conforꢀ
mational transformations in the coordination sphere of
the heteroatom and the solubility of polar organolead
intermediate 3. For this reason, to optimize the yields of
target products in reactions of reagent 2 with couꢀ
marins 6—9, we used, apart from pyridine, a number of
other bases: oꢀphenanthroline (3 equivalents with respect
to compound 2), pyridine—Et3N (3 equiv. each), pyriꢀ
dine—oꢀphenanthroline (3 equiv. each), and oꢀphenꢀ
anthroline—ButOK (3 and 1 equiv., respectively). It was
found that the yields of target products 14—17 did not
increase in the presence of the above systems of bases. In
contrast, reactions of 2ꢀ(bromomethyl)aryllead triacetates
with analogous organic substrates afforded good yields of
annulated benzopyranocoumarins.5b,c
sulfur have found new synthetic applications in the
postꢀUllmann chemistry in the last decade.1,2,18 Here we
showed for the first time that polyfunctional derivatives of
this series are suitable for the cascadeꢀtype synthesis of
lactones from enolizable substrates and phenols. Moderꢀ
ate yields of the target products (29—56%) correlate with
common total yields of three successive steps of the lacꢀ
tone synthesis without isolation of intermediates, which
undoubtedly makes the advanced approach more valuable.
Further investigations will be aimed at optimizing the
yields of the target products and searching for more effiꢀ
cient arylating reagents.
Experimental
The arylation of 3,5ꢀdimethoxyꢀ (10) and 3,4,5ꢀtriꢀ
methoxyphenols (11) gave lactones 18 and 19 in 41 and
29% yields, respectively. The arylation of 2ꢀnaphthol (12),
which usually reacts well with organolead reagents, afꢀ
forded compound 20 in 38% yield. With βꢀdiketone 13 as
a substrate, annulation product 21 was not obtained.
It should be noted that the arylation of 4ꢀhydroxyꢀ
coumarins 6—9 and phenols 10—12 with reagent 2 gave
only the corresponding lactones 14—20. The final reacꢀ
tion mixture contained trace amounts of the nonconsumed
substrates, while αꢀarylation products of the type 4 were
never detected. This fact suggests that the step 4 → 5 is
much faster than the step 3 → 4. The nonquantitative
yield of the target products is probably due to parallel side
processes.
A reaction that can compete with αꢀarylation proꢀ
ceeding through the formation of intermediate 3 may be
an intermolecular transesterification17 between substrates
6—12 and reagent 2 (Scheme 3). In this case, the subꢀ
strate molecule incorporated in the ester fragment loses
the nucleophilic center required for an attack on the lead
atom in reagent 2. Attempted isolation of organolead deꢀ
rivative 22 in the individual state was as unsuccessful
as with compound 2. The reactions of reagent 2 with
2ꢀnaphthol (12) and 4ꢀhydroxycoumarins 6 and 8 were
followed by acid hydrolysis giving rise to complex mixꢀ
tures of organic products from which we failed to isolate
acids formed upon the protolysis of intermediate 22.
In conclusion, note that arylating reagents based on
aryl derivatives of lead, bismuth, boron, iodine, and
NMR spectra were recorded on a Bruker ACꢀ200 spectromꢀ
eter (200.13 (1H) and 50.32 MHz (13C)) in CDCl3. Chemical
shifts are given on the δ scale with reference to Me4Si. 4ꢀHydrꢀ
oxycoumarin derivatives 6—9 were prepared according to known
procedures.4a,c,19 Commercial Hg(OAc)2, 2ꢀ(methoxycarboꢀ
nyl)phenylboronic acid, dimedone (13), and oꢀphenanthroline
(Lancaster) were used as purchased.
6H,11Hꢀ[2]Benzopyrano[4,3ꢀc][1]benzopyranꢀ6,11ꢀdione
(14). A mixture of lead tetraacetate (0.123 g, 0.28 mmol), merꢀ
cury diacetate (0.009 g, 0.028 mmol), and 2ꢀ(methoxycarboꢀ
nyl)phenylboronic acid (1) (0.05 g, 0.28 mmol) in freshly disꢀ
tilled CHCl3 (1 mL) was stirred at 45 °C for 1.5 h and then at
~20 °C for 12 h. 4ꢀHydroxycoumarin (6) (0.041 g, 0.2502 mmol)
and pyridine (0.066 g, 0.833 mmol) were added and the resulting
solution was stirred at 60—65 °C for 15 h. After the reaction was
completed, volatile compounds were removed under reduced
pressure and the residue was purified by column chromatoꢀ
graphy on SiO2 with AcOEt—light petroleum (3 : 7) as an eluent.
The yield of product 14 was 0.030 g (45%), colorless crystals,
m.p. 190 °C. Found (%): C, 72.67; H, 3.11. C16H8O4. Calcuꢀ
1
lated (%): C, 72.73; H, 3.05. H NMR, δ: 7.41—7.65 (m, 4 H,
H(2), H(3), H(4), H(8)); 7.92 (t, 1 H, H(9), J = 7.2 Hz); 8.18
(d, 1 H, H(1), J = 7.2 Hz); 8.41 (d, 1 H, H(10), J = 7.6 Hz);
9.20 (d, 1 H, H(7), J = 8.2 Hz). 13C NMR, δ: 113.4, 116.8,
120.3, 123.6, 125.0, 129.5, 133.1, 133.7 (CH); 101.1, 126.5,
130.2, 136.2, 152.5, 157.7, 159.0, 159.1 (quaternary C atoms).
Other lactones were obtained analogously.
2,4ꢀDimethoxyꢀ6H,11Hꢀ[2]benzopyrano[4,3ꢀc][1]benzoꢀ
pyranꢀ6,11ꢀdione (15). The yield was 42%, colorless crystals
decomposing at 200 °C. Found (%): C, 66.74; H, 3.90. C18H12O6.
Calculated (%): C, 66.67; H, 3.73. 1H NMR, δ: 3.90, 4.02
(both s, 3 H each, OMe); 6.41 (d, 1 H, H(3), J = 2.2 Hz); 6.52
(d, 1 H, H(1), J = 2.2 Hz); 7.58 (t, 1 H, H(8) or H(9),

Organoleadꢀassisted lactone synthesis
Russ.Chem.Bull., Int.Ed., Vol. 55, No. 9, September, 2006
1615
J = 7.5 Hz); 7.87 (td, 1 H, H(8) or H(9), J1 = 7.9 Hz, J2
=
References
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128.4, 129.8, 135.8 (CH); 98.0, 98.4, 119.3, 133.9, 156.0, 159.2,
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We are grateful to I. P. Beletskaya for fruitful disꢀ
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This work was financially supported by the Russian
Foundation for Basic Research (Project No. 06ꢀ03ꢀ32772)
and the INTAS (Grant 03ꢀ514915).

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Received May 23, 2006;
in revised form July 28, 2006