Organic base-catalyzed stereoselective isomerizations of 4-hydroxy-4-phenyl-but-2-ynoic acid methyl ester to (E)- and (Z)-4-oxo-4-phenyl-but-2-enoic acid methyl esters

Article abstract of DOI:10.1080/00397910500406583

We have developed a 1,4-diazabicyclo[2.2.2]octane (DABCO)-catalyzed isomerization of 4-hydroxy-4-phenyl-but-2-ynoic acid methyl ester to (E)-4-oxo-4-phenyl-but-2-enoic acid methyl ester and an N,N- diisopropylethylamine-catalyzed isomerization of the same

Full text of DOI:10.1080/00397910500406583

This article was downloaded by: [Pennsylvania State University]
On: 04 November 2014, At: 08:41
Publisher: Taylor & Francis
Informa Ltd Registered in England and Wales Registered Number: 1072954 Registered office:
Mortimer House, 37-41 Mortimer Street, London W1T 3JH, UK
Synthetic Communications: An International
Journal for Rapid Communication of
Synthetic Organic Chemistry
Publication details, including instructions for authors and subscription
information:
http://www.tandfonline.com/loi/lsyc20
Organic Base‐Catalyzed
Stereoselective Isomerizations of
4
‐Hydroxy‐4‐phenyl‐but‐2‐ynoic
Acid Methyl Ester to (E)‐ and
Z)‐4‐Oxo‐4‐phenyl‐but‐2‐enoic Acid Methyl
(
Esters
a
a
John P. Sonye & Kazunori Koide
a
Department of Chemistry , University of Pittsburgh , Pittsburgh,
Pennsylvania, USA
Published online: 16 Aug 2006.
To cite this article: John P. Sonye & Kazunori Koide (2006) Organic Base‐Catalyzed Stereoselective
Isomerizations of 4‐Hydroxy‐4‐phenyl‐but‐2‐ynoic Acid Methyl Ester to (E)‐ and (Z)‐4‐Oxo‐4‐phenyl‐but‐2‐enoic
Acid Methyl Esters, Synthetic Communications: An International Journal for Rapid Communication of Synthetic
Organic Chemistry, 36:5, 599-602
To link to this article: http://dx.doi.org/10.1080/00397910500406583
PLEASE SCROLL DOWN FOR ARTICLE
Taylor & Francis makes every effort to ensure the accuracy of all the information (the “Content”)
contained in the publications on our platform. However, Taylor & Francis, our agents, and our
licensors make no representations or warranties whatsoever as to the accuracy, completeness, or
suitability for any purpose of the Content. Any opinions and views expressed in this publication
are the opinions and views of the authors, and are not the views of or endorsed by Taylor &
Francis. The accuracy of the Content should not be relied upon and should be independently
verified with primary sources of information. Taylor and Francis shall not be liable for any
losses, actions, claims, proceedings, demands, costs, expenses, damages, and other liabilities
whatsoever or howsoever caused arising directly or indirectly in connection with, in relation to or
arising out of the use of the Content.
This article may be used for research, teaching, and private study purposes. Any substantial
or systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or
distribution in any form to anyone is expressly forbidden. Terms & Conditions of access and use
can be found at http://www.tandfonline.com/page/terms-and-conditions

w
Synthetic Communications , 36: 599–602, 2006
Copyright # Taylor & Francis Group, LLC
ISSN 0039-7911 print/1532-2432 online
DOI: 10.1080/00397910500406583
Organic Base-Catalyzed Stereoselective
Isomerizations of 4-Hydroxy-4-phenyl-but-
2
(
-ynoic Acid Methyl Ester to (E)- and
Z)-4-Oxo-4-phenyl-but-2-enoic Acid
Methyl Esters
John P. Sonye and Kazunori Koide
Department of Chemistry, University of Pittsburgh, Pittsburgh,
Pennsylvania, USA
Abstract: We have developed a 1,4-diazabicyclo[2.2.2]octane (DABCO)-catalyzed
isomerization of 4-hydroxy-4-phenyl-but-2-ynoic acid methyl ester to (E)-4-oxo-4-
phenyl-but-2-enoic acid methyl ester and an N,N-diisopropylethylamine-catalyzed iso-
merization of the same substrate to (Z)-4-oxo-4-phenyl-but-2-enoic acid methyl ester.
Keywords: 1,4-Diazabicyclo[2.2.2]octane, N,N-diisopropylethylamine, g-hydroxy-
a,b-alkynoic esters, isomerization, g-oxo-a,b-alkenoic esters
Both (E)- and (Z)-g-oxo-a,b,-alkenoic esters (E-A and Z-A, Figure 1) have
been used as intermediates in complex molecule syntheses
[1–5]
and also
[7]
found in peptidomimetics and natural products such as cytochalasins A,
[
6]
[
8]
[9]
[10]
[11]
L, vermiculine, pyrenophorin,
and A26771B.
Although Wittig-
have been employed to form
E-A, additional methods would involve g-hydroxy-a,b-alkynoic esters B as
[
6]
[12–14]
type condensations and other methods
[15,16]
precursors. These esters are easy to prepare
[
reactive functional groups.
g-hydroxy group and reduction of alkyne of B should afford E-A or Z-A.
even in the presence of
In principle, concomitant oxidation of the
16]
Received in the USA April 13, 2005
Address correspondence to Kazunori Koide, Department of Chemistry, University
of Pittsburgh, 219 Parkman Avenue, Pittsburgh, PA 15260, USA. E-mail: koide@pitt.
edu
5
99

6
00
J. P. Sonye and K. Koide
Figure 1. Structures of (E)- and (Z)-g-oxo-a,b-alkensic esters and g-hydroxy-a,b-
alkynoic esters.
Such transformations have been achieved by three methods: (1) treatment of B
with 0.5 equiv of Et N at 238C, generating only E-A after distillation (our
3
[
17]
study and others
during distillation in the presence of Et N);
indicate that Z-A might have been isomerized to E-A
(2) treatment of B with 1
[17]
3
[18]
equiv of n-Bu N at 238C, generating a mixture of E-A and Z-A;
(3)
treatment of B with 3 mol% of Rh(PPh ) Cl, air-sensitive tri-n-butyl-
3
3
3
[
19]
[20]
phosphine, and high temperature (1108C), generating E-A.
these methods can be used to prepare E-A, there are few general methods
to prepare Z-A stereoselectively. Herein, we report convenient organic
base-catalyzed methods to convert B to E-A and B to Z-A stereoselectively.
Although
[21]
During our efforts to develop diversity-oriented synthetic pathways using
(Equation (1)) as a pluripotent substrate, we found that treatment of 1 with
1
Et N in CH Cl at 238C gave E-2 and Z-2 in approximately 70% yield
3
2
2
(
E:Z ¼ 2 : 1). After some screening efforts, we found that 10 mol% of
DABCO catalyzed such transformation in a highly E-selective manner
(
E:Z¼ 33 : 1) in 70% yield (DMSO, 238C, 7 h). This is presumably a thermo-
dynamically controlled reaction because the treatment of Z-2 with 10 mol%
DABCO in DMSO gave the same product distribution in 77% yield.
Catalytic i-Pr NEt (10 mol%) in DMSO/H O (4 : 1) isomerized 1 to Z-2
2
2
and E-2 in 47% combined yield in 10 : 1 ratio in favor of Z-2. In the absence of
water, the Z : E stereoselectivity is only 2 : 1. Although the yield is currently
moderate (not optimized), we found that the E-2 was intact under similar
conditions (10 mol% i-Pr NEt, DMSO/H O ¼ 2 : 1, 238C, 5 d), excluding
2
2
the possibility that E-2 selectively decomposed under the reaction conditions.
It is noteworthy that the hydrogeratian of 3 using Lindlar’s catalyst gave the
mixture of E-2 and Z-2 in a 5 : 1 ratio presumably because of the quinoline-
catalyzed isomerization of Z-2 to E-2 (Equation (2)).

Stereoselective Isomerizations
601
We are currently studying the scope and mechanisms of these two new
[
24]
processes, which will be reported in due course.
developed the first metal-free catalytic processes for the stereoselective
In summary, we have
transformation of 1 to E-2 and Z-2.
EXPERIMENTAL
Conversion of 1 to E-2. DABCO (2.8 mg, 0.0250 mmol) was added to a
solution of 1 (47.6 mg, 0.250 mmol) in DMSO (1.0 mL) at 238C, and the
resulting solution was stirred at the same temperature for 7 h. The reaction
was then quenched with 0.1 N HCl (0.3 mL) and water (20 mL), and the
resulting aqueous mixture was extracted with Et O (30 mL ꢀ 5). The
2
combined organic layers were then washed with water (20 mL ꢀ 3), dried
over Na SO , filtered, and evaporated in vacuo. The resulting residue was
2
4
purified by silica-gel chromatography (5 ! 20% EtOAc in hexanes) to
1
generate E-2 (33.2 mg, 70%) as a pale yellow oil. The H NMR spectrum
[22]
of this product was consistent with the literature.
Conversion of 1 to Z-2. i-Pr NEt (9.0 mL, 0.052 mmol) was added to a
2
solution of 1 (99.7 mg, 0.52 mmol) in DMSO (0.8 mL) and water (0.2 mL)
at 238C, and the resulting solution was stirred at the same temperature far
2
d. The reaction was then quenched with 0.1 N HCl (0.6 mL) and water
(
(
(
20 mL), and the resulting aqueous mixture was extracted with EtOAc
15 mL ꢀ 3). The combined organic layers were then washed with water
20 mL ꢀ 1), brine (20 mL ꢀ 1), dried over Na SO , filtered, and evaporated
2
4
in vacuo. The resulting residue was purified by silica-gel chromatography
(
5 ! 20% EtOAc in hexanes) to generate a mixture of Z-2 and E-2
1
(
47.2 mg, 47%; Z-2 : E-2 ¼ 10 : 1, determined by H NMR) as a pale yellow
1
oil. The H NMR spectrum of these products was consistent with the literature
[
22,23]
and showed no detectable impurities.
REFERENCES
1
2
3
4
. Rubinstein, R.; Haviv, F.; Ginsburg, D. Reactions of thebaine with cis- and trans-
disubstituted dienophiles. Tetrahedron 1974, 30, 1201–1210.
. Marvel, C. S.; Galun, A. B. Copolymerization of trans-methyl b-benzoylacrylate.
J. Org. Chem. 1955, 20, 587–590.
. Mamaghani, A. Enzymatic kinetic resolution of aromatic substituted narbornene
mono-esters using pig’s liver esterase. Tetrahedron 2002, 58, 147–151.
. Harwood, L. M.; Jackson, B.; Jones, G.; Prout, K.; Thomas, R. M.; Witt, F. J.
Synthetic approaches to phorbols via the intramolecular Diels–Alder reaction of
furans: Influence of the dienophile upon the stereochemical control. Chem.
Commun. 1990, 8, 608–610.
5
. Roush, W. R.; Coe, J. W. Studies of an intramolecular Diels–Alder approach to the
nargenicins: Involvement of boatlike transition states in the cyclizations of substi-
tuted 1,7,9-decatrien-3-ones. J. Org. Chem. 1989, 54, 915–930.

6
02
J. P. Sonye and K. Koide
6
7
. Vabeno, J.; Brisander, M.; Lejon, T.; Luthman, K. Diastereoselective reduction of
a chiral N-Boc-protected d-amino-a,b-unsaturated g-keto ester Phe-Gly dipeptido-
mimetic. J. Org. Chem. 2002, 67, 9186–9191.
. Aldridge, D. C.; Armstrong, J. J.; Speake, R. N.; Turner, W. B. The cytochalasins,
a new class of biologically active mould metabolites. Chem. Commun. 1967,
2
6–27.
8
9
. Fex, T. Structures of cytochalasin K, L, and M, isolated from Chalara microspora.
Tetrahedron Lett. 1981, 22, 2703–2706.
. Boeckman, R.K., Jr.; Fayos, J.; Clardy, J. A revised structure of vermiculine. A
novel macrolide dilactone antibiotic from Penicillium vermiculatum. J. Am.
Chem. Soc. 1974, 96, 5954–5956.
1
1
1
1
0. Nozoe, S.; Hirai, K.; Tsuda, K. The structure of pyrenophorin. Tetrahedron Lett.
965, 51, 4675–4677.
1. Michel, K. H.; Demarco, P. V.; Nagarajan, J. The isolation and structure elucida-
tion of macracyclic lactone antibiotic A26771B. J. Antibiot. 1977, 30, 571–575.
2. Bartlett, P. A. Synthesis of b-acylacrylic esters and a,b-butenolides via b-keto
sulfoxide alkylation. J. Am. Chem. Soc. 1976, 98, 3305–3312.
3. Kulinkovich, O. G.; Tischenko, I. G.; Romashin, J. N.; Savitskaya, L. N. Con-
venient method for the preparation of methyl trans-4-oxo-2-alkenoates.
Synthesis 1986, 378–379.
1
1
1
1
1
1
4. Greene, A. E.; Le Drian, C.; Crabbe, P. Conversion of carbalkoxymethyl groups to
g-oxocrotonate derivatives. J. Org. Chem. 1980, 45, 2713–2715.
5. Midland, M. M.; Tramontano, A.; Cable, J. R. Synthesis of alkyl 4-hydroxy-2-
alkynoates. J. Org. Chem. 1980, 45, 28–29.
6. Shahi, S. P.; Koide, K. A mild method for the preparation of g-hydroxy-a,b-
acetylenic esters. Angew. Chem., Int. Ed. 2004, 43, 2525–2527.
7. Nincham, A. W.; Raphael, R. A. Compounds related to penicillic acid. Part IV.
Synthesis of a phenyl analogue. Chem. Commun. 1949, 118–121.
8. Arcadi, A.; Cacchi, S.; Marinelli, F.; Misiti, D. The reaction of alkyl 4-hydroxy-2-
alkynoates and 4-hydroxy-2-alkyn-l-ones with palladium tributylammonium
formate and with tributylamine: Preparation of 1,4-dicarbonyl compounds.
Tetrahedron Lett. 1988, 29, 1457–1460.
1
2
9. Buckler, S. A. Autoxidation of trialkylphosphines. J. Am. Chem. Soc. 1962, 84,
093–3097.
3
0. Saiah, M. K. E.; Pellicciari, R. Rhodium-catalyzed redox isomerization of hydroxy
alkynes to trans keto and hydroxy vinyl esters. A short and stereoselective
synthesis of dipeptide isosteres. Tetrahedron Lett. 1995, 36, 4497–4500.
1. Scarpati, R.; Graziano, M. L.; Iesce, M. R.; Cermola, F.; Piazza, A. Photosensitized
oxidation of furans: A simple method for a one-pot synthesis of functionalized
methyl cis-4-oxoalk-2-enoates. Synthesis 1995, 439–443.
2
2
2
2
2. Bonete, P.; Najera, C. Lithium 3-lithio-3-tosylalkanoates: b-acylvinyl anion
equivalents of b-lithiated a,b-unsaturated carboxylic acids. J. Org. Chem 1994,
5
9, 3202–3209.
3. Sestrick, M. R.; Miller, M.; Hegedus, L. S. Photochemical reactions of chromium-
alkoxycarbene complexes with stabilized ylides to produce push–pull captodative
allenes. J. Am. Chem. Soc. 1992, 114, 4079–4088.
4. Sonye, J. P.; Koide, K. On the mechanism of DABCO-catalyzed isomerization of
g-hydroxy-a,b-alkynoates to g-oxo-a,b-(E)-alkenoates. Org. Lett. 2006, 8 (3),
1
99–202.