ZnII- and AuI-catalyzed regioselective hydrative oxidations of 3-En-1-ynes with selectfluor: Realization of 1,4-dioxo and 1,4-oxohydroxy functionalizations

Article abstract of DOI:10.1002/chem.201304322

Catalytic 1,4-dioxo functionalizations of 3-en-1-ynes to (Z)- and (E)-2-en-1,4-dicarbonyl compounds are described. This regioselective difunctionalization was achieved in one-pot operation through initial alkyne hydration followed by in situ Selectfluor oxidation. The presence of pyridine alters the reaction chemoselectivity to give 4-hydroxy-2-en-1-carbonyl products instead. A cooperative action of pyridine and Zn^II assists the hydrolysis of key oxonium intermediate.

Full text of DOI:10.1002/chem.201304322

DOI: 10.1002/chem.201304322
Communication
&
Synthetic Methods
ZnII- and AuI-Catalyzed Regioselective Hydrative Oxidations of
3-En-1-ynes with Selectfluor: Realization of 1,4-Dioxo and 1,4-
Oxohydroxy Functionalizations
Appaso Mahadev Jadhav, Sagar Ashok Gawade, Dhananjayan Vasu, Ramesh B. Dateer, and
Rai-Shung Liu*[a]
picted by state VII, is influenced by catalytic amounts of pyri-
dine (Scheme 1).
Abstract: Catalytic 1,4-dioxo functionalizations of 3-en-1-
ynes to (Z)- and (E)-2-en-1,4-dicarbonyl compounds are
described. This regioselective difunctionalization was
achieved in one-pot operation through initial alkyne hy-
dration followed by in situ Selectfluor oxidation. The pres-
ence of pyridine alters the reaction chemoselectivity to
give 4-hydroxy-2-en-1-carbonyl products instead. A coop-
erative action of pyridine and ZnII assists the hydrolysis of
key oxonium intermediate.
Among these products, electron-deficient alkenes 7 and 7’
have found widespread use in Diels–Alder reactions and Mi-
chael acceptors[10] whereas 4-carbonyl-2-en-1-amides 3 are the
key intermediates for naturally occurring ceruleinin, tetrahydro-
ceruleinin and related compounds.[11] 4-Hydroxy-2-en-1-amides
4 were also intermediates for the synthesis of (+)-pinellic acid
and (+)-coriolic acid.[12]
Table 1 shows the 1,4-dioxo functionalization of an activated
3-en-1-ynamide 1a; we employed Selectfluor as the oxidant[13]
because of its tolerance of water. In a one-pot operation, 3-en-
1-yne 1a was treated with a catalyst (5 mol%) in CH3CN/water
(3:1) at 508C for 0.3–14 h (t1) to complete an alkyne hydration.
To this solution was added Selectfluor (2.0 equiv) to promote
an in situ oxidation over a suitable period (t2 =1–10 h). For
Zn(OTf)2, the hydration was complete within 14 h, giving 3-en-
1-amide 2a in 95% yield (entry 1). A Selectfluor oxidation of
this amide in situ for a brief period (t2 =1 h), afforded cis-4-
oxo-2-en-1-amide 3a’ and its trans isomer 3a in 74 and 16%
yield, respectively (entry 2). An extended oxidation (t2 =12 h,
entry 3) gave trans-2-en-1,4-dicarbonyl 3a exclusively in 89%
yield. Cis-configured alkene 3a’ was evidently the primary
product, which was convertible to its trans-isomer 3a under
the conditions. We tested the reactions on PPh3AuOTf, result-
ing in 3-en-1-amide 2a in moderate yield (55%) in a brief
period (t1 =0.5 h, entry 4), further giving trans-alkene 3a in
43% yield after the oxidation (entry 5). IPrAuOTf (IPr=1,3-
bis(di-isopropylphenyl)imidazol-2-ylidene) and PtCl2/CO were
Considerable interest has focused on the regioselective 1,2-oxo
functionalizations of alkynes to generate a new carbonyl
group. Numerous reactions have been developed for the syn-
theses of 1,2-dicarbonyl products (I),[1–3] with scattered reports
on a-hydroxylcarbonyl,[4] a-aminocarbonyl,[5] a-iminocarbon-
yl[5a] or a-arylcarbonyl[6] derivatives (II–V), (Scheme 1). 1,2-Dicar-
bonyl species I are readily available from catalytic oxidations of
alkynes with O2,[1]organic[2] or inorganic oxidants.[3] 1,3-Enynes
are readily available from unsaturated four-carbon motifs; con-
ceivably, their oxo functionalizations pose an eminent chal-
lenge because of two regioselective routes, that is, 1,2- versus
1,4-additions. The preceding oxidations on 3-en-1-ynes were
accessible only to 1,2-addition products,[7,8] as exemplified by
Scheme 1. Regioselective control of 1,4-difunctionalizations on
3-en-1-ynes remains a formidable task with no literature prece-
dent.
We report the first 1,4-dioxo and 1,4-oxohydroxy reactions
of readily available 3-en-1-ynes 1 and 5 to furnish Z- and E-2-
en-1,4-dicarbonyl compounds 3 and 7/7’ and E-4-hydroxy-2-
en-1-amides 4. Our synthetic advance adopts a prior hydration
strategy,[9] followed by a Selectfluor oxidation in a one-pot op-
eration [see (i) and (ii) in Scheme 1]. Notably, the chemoselec-
tivity of the carbonyl-assisted alkene fluorination in step (ii), de-
[a] Dr. A. M. Jadhav, S. A. Gawade, Dr. D. Vasu, Dr. R. B. Dateer,
Prof. Dr. R.-S. Liu
Department of Chemistry
National Tsing Hua University
Hsinchu, 30013 (Taiwan)
Fax: (+886)3-5711082
E-mail: rsliu@mx.nthu.edu.tw
Supporting information for this article is available on the WWW under
http://dx.doi.org/10.1002/chem.201304322.
Scheme 1. 1,2- and 1,4-oxo functionalizations.
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Communication
added before additional heating for 10 h. Entries 1–4
show the generality of this 1,4-dioxo reaction to vari-
ous sulfonamide groups including NR1R2 =NMs(nBu),
NTs(Ph), NTs(benzyl), NTs(cyclopropyl), giving desired
4-oxo-2-en-1-amides 3b–e in satisfactory yields (74–
91%, entries 1–4). These catalytic 1,4-difunctionaliza-
tions were further extendable to substrates 1 f–h
bearing electron-deficient phenyl substituents X=F,
Cl, and Br; their 1,4-dicarbonyl products 3 f–h were
obtained in good yields (79–88%, entries 5–7). The
same reactions also worked for 3-en-1-ynamides 1i
and j bearing a varied electron-rich phenyl group
(X=Me, OMe), giving compounds 3i and j in 82–
88% yield (entries 8 and 9). For substrate 1k bearing
an ortho-methoxy substituent, its resulting product
3k was obtained in 87% yield. The reactions were
applicable to 2-thiophene and 2-benzothiophene de-
rivatives 1l and m delivered 4-oxo-2-en-1-amides 3l
and m in 81–83% yield.
Table 1. Conditions for 1,4-dioxo functionalizations.
Catalyst
t1 [h]
t1 [h]
Compounds [%][b]
2a
3a’
3a
4a
1
2
3
4
5
6
7
8
9
Zn(OTf)2
Zn(OTf)2
14
14
14
0.5
0.5
2
2
0.3
0.3
0
1
12
0
1
0
5
0
5
95
–
–
74
–
–
–
–
49
–
–
16
89
–
43
–
23
–
42
–
–
–
–
–
–
–
–
5
Zn(OTf)2
PPh3 AuOTf
PPh3 AuOTf
IPrAuOTf
IPrAuOTf
PtCl2/CO
PtCl2/CO
–
55
–
91
–
98
–
14
[a] MeCN/H2O=3:1, [1a]=0.07m. [b] Product yields are reported after separation on
a silica-gel column.
We prepared additional 3-en-1-yn-1-amides 1n
and o bearing an aliphatic group to expand the reac-
tion scope, but the use of Selectfluor failed to
promote a clean oxidation sequence. With water
soluble DABCO.Br2 (bis-bromine-1,4-diazabicyclo-
[2.2.2]octane), the desired 4-oxo-2-en-1-amides 3n
and o were obtained in 75 and 72% yield respective-
ly [Eq. (1), (2)].
Table 2. ZnII-catalyzed 1,4-dioxo functionalizations.
We tested the reaction on an unactivated 3-en-1-
yne 5a to enhance its synthetic utility [Eq. (3)];
IPrAuOTf (5 mol%, IPr=1,3-bis(di-isopropylphenyl)-
imidazol-2-ylidene) replaced Zn(OTf)2 to attain an ef-
fective alkyne hydration. The hydration for 3-en-1-
yne 5a was complete in CH3CN/H2O (3:1, 808C) for
10 h; the treatment of this resulting solution in-situ
with Selectfluor (2 equiv) at 288C (10 h), afforded
only cis-4-oxo-2-en-1-one 7a’ in 79% yield. If the Se-
lectfluor oxidation was performed in CH3CN/H2O (3:1,
508C) for 12 h, trans-alkene 7a was obtained with
78% yield. Herein, the hydration product 6a was iso-
lated for spectral characterization.
Table 3 shows the generalization of one-pot syn-
theses of cis-4-oxo-2-en-1-ones 7b’–k’ using unacti-
vated 3-en-1-ynes 5b–k and IPrAuOTf (5 mol%) in
MeCN/H2O (3:1). The cis-olefin configurations are re-
vealed by the proton coupling constants J=11–
[a] MeCN/H2O=3:1. [1]=0.07m, 5 mol% Zn(OTf)2. [b] Product yields are reported after
separation on a silica-gel column.
excellent hydration catalysts (t1 =0.3–3 h) to give 3-en-1-amide
2a in 91–98% yield (entries 6 and 8). Upon Selectfluor oxida-
tions, IPrAuOTf gave desired compounds 3a and 3a’ in 23 and
49% yield, respectively (entry 7), whereas PtCl2/CO gave three
products, including 3a (42%), 3a’ (14%) and 4-hydroxy-2-en-1-
amide 4a (5%, entry 9). Although Zn(OTf)2 catalyzed the
alkyne hydration slowly, it gave the best yield (3a, 89%) over
the entire sequence.
12 Hz; the time t1 and t2 referred to complete consumption of
3-en-1-ynes 5 and their hydration intermediates 6, respectively.
For substrates 5b and c bearing alterable styryl Ar1 groups
(X=OMe and Me), their corresponding products 7b’ and c’
were obtained in 81–86% yield (entries 1 and 2). The reactions
were extendable to their electron-deficient styryl analogues 5d
and e (X=F and CF3), giving desired products 7d’ and e’ in
72–73% yield (entries 3 and 4). These hydrative oxidations also
worked for enynes 5 f–h bearing variable alkynyl Ar2 substitu-
ents (Y=OMe, Me and F), affording compounds 7b’,c’, and d’
in 71–74% yield (entries 5–7). The reactions were also applica-
ble to cis-4-oxo-2-en-1-ones 7i’ and j’ bearing 4-methoxy- or 4-
We prepared additional E-configured 3-en-1-ynamides 1b–m
to assess the substrate scope (Table 2). In a one-pot operation,
3-en-1-ynes 1 were heated with Zn(OTf)2 catalyst in MeCN/H2O
(3:1) at 508C for 14 h; to this solution, Selectfluor (2 equiv) was
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Communication
[Eq. (5)]. When Selectfluor was used in sufficient pro-
portion (2 equiv), cis-4-oxo-2-en-1-one 7a’ was ob-
tained in 83% yield [Eq. (6)]. We are aware of no
precedent for electrophile-induced cyclizations of 3-
en-1-carbonyl species to form furan derivatives.[14–16]
Accordingly, we propose a mechanism in Scheme 2
involving a carbonyl-assisted alkene fluorination as
represented by species B. To rationalize the interme-
diacy of 2-aminofuran 8’, we envisage that Selectfluor
attacks the olefin of intermediate 2a to form F+-coor-
dinated alkene[10] A with a positive character at its
benzylic carbon, further inducing an amide attack to
form an oxonium species B.[13,17] After delivering an
“fluorinum” ion, the remaining [N]=1,4-diazabicyclo-
[2,2,2]octanium, acted as a base to facilitate the de-
protonation of this oxonium species to give 4-fluoro-
fluorophenyl groups; the yields were 76–84% (en-
tries 8 and 9). A heteroaryl group as in species 7k’
was compatible with this reaction providing the
product in 54% yield.
We performed control experiments to elucidate
the mechanism of 1,4-dioxo functionalizations
[Eq. (4)]. Treatment of 3-en-1-amide 2a with Select-
fluor (2 equiv) in MeCN (508C, 0.8 h) gave cis-4-oxo-2-
en-1-amide 3a’ in 89% yield exclusively; Zn(OTf)2
was unnecessary herein. cis-Alkene 3a’ is readily con-
verted to its trans isomer 3a with Zn(OTf)2 in MeCN/
H2O (3:1) at 508C (12 h). Structural analysis of cis-olefin 3a’ led
us to postulate that an aminofuran species is a likely precursor
that is prone to Selecfluor oxidation to give 3a’. With 3-en-1-
one 6a, its oxidation with Selectfluor (1.0 equiv) in MeCN/H2O
(3:1) allowed the isolation of a furan derivative 8 in 51% yield
dihydrofuran C. A subsequent loss of HF from species C is ex-
pected to occur readily because aromatic aminofuran 8’ is
formed. A subsequent Selectfluor oxidation on this furan af-
forded cis-4-oxo-2-en-1- amide 3a’ via intermediates D and E.
Interestingly, nitrogen-base additives altered the oxidation
chemoselectivity as depicted in Table 4. Our vigorous trials in-
dicated performing the reaction with an initial treatment of 3-
en-1-ynamide 1a with a mixture of Selectfluor (2.0 equiv) and
additives (10 mol%) in MeCN/H2O (508C, 3:1) for 16–20 h.[15]
Et3N and DBU, with 10 mol% loading, led to formation of E-
configured 4-hydroxy-2-en-1-amide 4a in 47–58% yield (en-
tries 1–2) whereas undesired 4-oxo-2-en-1-amides 3a’ and 3a
were also present in significant portions (12–18%). Gratifyingly,
the use of pyridine (10 mol%) gave desired 4a with 83% yield
(entry 3). We tested the reaction with PtCl2/CO because of its
hydration activity; Amide 4a was formed in low yield (23%).
The structure of this amide was carefully determined by 1H
NOE-effect.
Table 3. One-pot syntheses of cis-4-oxo-2-en-1-ones.
We assess the generality of this ZnII-catalyzed 4-hydroxy-1-
oxo functionalization using the same 3-en-1-ynamides 1b–m
(see Table 2). As shown in Table 5, this altered chemoselectivity
arose from added pyridine (10 mol%). In some instances (en-
tries 1, 4, 6, and 7), we obtained 4-oxo-2-en-1-amides 3 and 3’
with minor proportions (5–9%). The reaction was tolerant of
modifications to the sulfonamide group, giving E-configured 4-
hydroxy-2-en-1-amides 4b–e in 65–74% yield. The reactions
worked well for 3-en-1-ynamides 1 f–k bearing an electron-de-
ficient and -rich phenyl group, giving desired products 4 f–k
with 73–83% yield (entries 5–10). For heteroaryl derivatives 1l
[a] MeCN/H2O=3:1. [b] These values refer to t1(h)/t2(h). [c] Product yields
are reported after a silica-gel column.
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ence of pyridine, Zn(OTf)2 would form a complex
(TfO)2Zn(py)2 to activate the protonation of F and H,
ultimately giving 4-hydroxy-2-en-1-amide 4a through
a loss of HF from key intermediate I. An alternative
route involving an allylic oxidation of isomerization
alkene 2a’ is excluded according to a control experi-
ment (Scheme 3, entry 1).
In summary, new 1,4-oxo functionalizations of 3-
en-1-ynes have been developed based on a hydrative
oxidation approach. The one-pot dioxo reactions
were applicable to various 3-en-1-ynes including un-
activated 3-aryl-3-en-1-ynes, giving Z- or E-configured
Scheme 2. A mechanism for 1,4-dioxo reaction.
and m, resulting products 4l and m were produced
with 76–77% yield.
Table 5. 4-Hydroxy-1-oxo functionalizations.
As shown in Scheme 3, pyridine alone (10 mol%)
impeded the oxidation of 3-en-1-amide 2a, leading
to 63% recovery, with no olefin isomerization occur-
ring for species 2a (entry 1). Notably, Zn(OTf)2 pro-
moted this oxidation to afford the desired 4a in 78%
yield together with 3a/3a’ in 6–8% yield. The Select-
fluor oxidation of starting 2a in MeCN/H2O* (3:1,
O*=23% 17O) gave 17O-enriched 4a, of which the
17O NMR revealed two major peaks, assignable to C=
O (d=377 ppm) and CꢀOH (d=29 ppm). Under the
ZnII/pyridine conditions, there is no oxygen exchange
between water and this 17O-enriched 4a. Mass-spec-
tral analysis revealed that 17O-enriched 4a contained
one 17O atom according to its H2O* isotope source.
The effect of Zn(OTf)2 is rationalized in a proposed
mechanism (Scheme 4). In the absence of Zn2+, pyri-
dine likely reacted with water to generate hydroxide
to decompose Selectfluor. Before the C(3)-H
deprotonation of oxonium species B with [N]=1,4-
diazabicyclo[2,2,2]octanium, as shown by the B!C
conversion (Scheme 2), water might attack this oxoni-
um species rapidly through two paths (i) or (ii) ac-
cording to our 17O labeling results. In the presence of
Selectfluor and Zn(OTf)2, such an acidic medium in-
hibits a proton loss of species F and H, thus inhibit-
ing the F!G and H!I transformations. In the pres-
[a] MeCN/H2O=3:1, [1]=0.07m. [b] product yields are reported after separation on
a silica-gel column.
2-en-1,4-dicarbonyl compounds selectively. Our mechanistic
analysis supported an initial formation of furan intermediates,
generated from carbonyl-assisted alkenyl fluorinations of hy-
dration intermediates. The addition of pyridine altered the oxi-
dation selectivity to give E-4-hydroxy-2-en-1-amides instead. A
cooperative action of pyridine and ZnII was suggested to medi-
ate the hydrolysis of key oxonium intermediates B. This work
reports the first successful 1,4-oxo functionalization of readily
Table 4. Additive effects on chemoselectivity.
5 mol%
cat.
10 mol%
additive
t [h]
Compound [%][b]
3a’
3a
4a
available 3-en-1-ynes to form highly functionalized alkenes.
1
2
3
4
Zn(OTf)2
Zn(OTf)2
Zn(OTf)2
PtCl2/CO
Et3N (10)
DBU (10)
Pyridine (10)
Pyridine (10)
20
20
18
16
14
18
3
12
15
4
47
58
83
Acknowledgements
12
34
23
We thank the National Science Council, Taiwan for financial
[a] MeCN/H2O=3:1, [1a]=0.07m. [b] Product yields are reported after
support of this work.
separation on a silica-gel column.
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[8] Besides 1,2-oxo reactions on 3-en-1-ynamide,[7] a gold-cata-
lyzed oxoamination reaction occurred with a 1,2-addition
mode. The spectral data of compound 9 is provided in the
Supporting Information.
[9] Selected examples: a) W. E. Brenzovich, Jr., Angew. Chem.
2012, 124, 9063; Angew. Chem. Int. Ed. 2012, 51, 8933; b) N.
Marion, R. S. Ramꢁn, S. P. Nolan, J. Am. Chem. Soc. 2009,
131, 448; c) A. Leyva, A. Corma, J. Org. Chem. 2009, 74,
2067; d) E. Mizushima, K. Sato, T. Hiyashi, M. Tanaka, Angew.
Chem. 2002, 114, 4745; Angew. Chem. Int. Ed. 2002, 41,
4563; e) L. Li, S. Herzon, J. Am. Chem. Soc. 2012, 134, 17376.
[10] For synthesis of 1,4-en-diones, see selected examples: a) K.
Xu, Y. Fang, Z. Yan, Z. Zha, Z. Wang, Org. Lett. 2013, 15,
2148; b) B. Crone, S. F. Kirsch, Chem. Commun. 2006, 764;
c) J. Q. Yu, E. J. Corey, J. Am. Chem. Soc. 2003, 125, 3232;
d) W. Baratta, A. D. Zotto, P. Rigo, Chem. Commun. 1997,
2163.
Scheme 3. The effect of Zn(OTf)2 and pyridine.
[11] a) A. A. Jakubowski, F. S. Guziec, Jr., M. Sugiura, C. C. Tam, M.
Tishler, J. Org. Chem. 1982, 47, 1221; b) D. S. Lawrence, J. T.
Zilfou, C. D. Smith, J. Med. Chem. 1999, 42, 4932.
[12] a) Y. Bennani, K. B. Sharpless, Tetrahedron Lett. 1993, 34,
2083; b) S. K. Sunnam, K. R. Prasad, Synthesis 2013, 45, 1991.
[13] Recent examples on alkene fluorination; see a) R. P. Singh,
J. M. Shreeve, Acc. Chem. Res. 2004, 37, 31; b) V. Rauniyar,
A. D. Lackner, G. L. Hamilton, F. D. Toste, Science 2011, 334,
1681; c) T. Honjo, R. J. Phipps, V. Rauniyar, F. D. Toste, Angew.
Chem. 2012, 124, 9822; Angew. Chem. Int. Ed. 2012, 51, 9684;
d) Y. Peng, L. Cui, G. Zhang, L. Zhang, J. Am. Chem. Soc.
2009, 131, 5062; e) G. Zhang, L. Cui, Y. Wang, L. Zhang, J.
Am. Chem. Soc. 2010, 132, 1474; f) T. de Haro, C. Nevado,
Angew. Chem. 2011, 123, 936; Angew. Chem. Int. Ed. 2011, 50,
906; g) W. Kong, P. Feige, T. de Haro, C. Nevado, Angew.
Chem. 2013, 125, 2529; Angew. Chem. Int. Ed. 2013, 52, 2469;
h) J. R. Wolstenhulme, J. Rosenqvist, O. Lozano, J. Hupeju, N. Wurz, K. M.
Engle, G. W. Pidgeon, P. R. Moore, G. Stanford, V. Gouverneur, Angew.
Chem. 2013, 125, 9978; Angew. Chem. Int. Ed. 2013, 52, 9796.
[14] See recent reviews on furan synthesis, ref. [14a] refer to electrophilic in-
duced cyclizations; a) B. Godoi, R. F. Schumacher, G. Zeni, Chem. Rev.
2011, 111, 2937; b) R. C. D. Brown, Angew. Chem. 2005, 117, 872; Angew.
Chem. Int. Ed. 2005, 44, 850; c) D. M. D’Souza, T. J. J. Mꢂller, Chem. Soc.
Rev. 2007, 36, 1095; d) S. F. Kirsch, Org. Biomol. Chem. 2006, 4, 2076;
e) B. A. Keay, Chem. Soc. Rev. 1999, 28, 209.
[15] Selected examples: a) P. Lenden, D. A. Entwistle, M. C. Willis, Angew.
Chem. 2011, 123, 10845; Angew. Chem. Int. Ed. 2011, 50, 10657; b) X.
Huang, B. Peng, M. Luparia, L. F. R. Gomes, L. F. Veiros, N. Maulide,
Angew. Chem. 2012, 124, 9016; Angew. Chem. Int. Ed. 2012, 51, 8886;
c) A. S. K. Hashmi, P. Sinha, Adv. Synth. Catal. 2004, 346, 432; d) A. S. K.
Hashmi, Angew. Chem. 1995, 107, 1749; Angew. Chem. Int. Ed. Engl.
1995, 34, 1581.
[16] Recent reviews on electrophiles-induced cyclizations of alkenes, see:
a) C.-K. Tan, Y.-Y. Yeung, Chem. Commun. 2013, 49, 7985; b) A. Chianese,
S. J. Lee, M. R. Gagnꢃ, Angew. Chem. 2007, 119, 4118; Angew. Chem. Int.
Ed. 2007, 46, 4042.
Scheme 4. A mechanism for alkene oxidation.
Keywords: 1,4-enediones · 1,4-oxohydroxy · 3-en-1-ynes ·
hydrative oxidations · regioselective difunctionalizations
[1] For O2 as the oxidant, see: a) W. Ren, Y. Xia, S.-J. Ji, Y. Zhang, X. Wan, J.
Zhao, Org. Lett. 2009, 11, 1841; b) C. Zhang, N. Jiao, J. Am. Chem. Soc.
2010, 132, 28–29.
[2] a) C.-F. Xu, M. Xu, Y.-X. Jia, C.-Y. Li, Org. Lett. 2011, 13, 1556; b) S. Shi, T.
Wang, W. Yang, M. Rudolph, A. S. K. Hashmi, Chem. Eur. J. 2013, 19,
6576; c) P. W. Davies, A. Cremonesi, N. Martin, Chem. Commun. 2011, 47,
379.
[3] a) Z. F. Al-Rashid, W. L. Johnson, R. P. Hsung, Y. G. Wei, P.-Y. Yao, R. H. Liu,
K. Zhao, J. Org. Chem. 2008, 73, 8780; b) Z. Zhu, J. Espenson, J. Org.
Chem. 1995, 60, 7728; c) S. Dayan, I. B. David, S. Rozen, J. Org. Chem.
2000, 65, 8816; d) Z. Wan, C. Jones, D. Mitchell, J. Y. Pu, T. Y. Zhang, J.
Org. Chem. 2006, 71, 826.
[4] Y. Kita, T. Yakura, H. Terashi, J.-I. Haruta, Y. Tamura, Chem. Pharm. Bull.
1989, 37, 891.
[5] a) A. Mukherjee, R. B. Dateer, R. Chaudhuri, S. Bhunia, S. N. Karad, R.-S.
Liu, J. Am. Chem. Soc. 2011, 133, 15372; b) H.-S. Yeom, E. So, S. Shin,
Chem. Eur. J. 2011, 17, 1764.
[6] a) S. Bhunia, C.-J. Chang, R.-S. Liu, Org. Lett. 2012, 14, 5522; b) B. Lu, Y.
Li, Y. Wang, D. H. Aue, Y. Luo, L. M. Zhang, J. Am. Chem. Soc. 2013, 135,
8512–8524; c) A. B. Cuenca, S. Monsterrat, K. M. Hossain, G. Mancha, A.
Lledꢁs, M. Medio-Simꢁn, G. Ujaque, G. Asensio, Org. Lett. 2009, 11,
4906.
[17] Treatment of 3-en-1-ester with I2 gave 4-iodo-g-lactone; see: a) S. Ma, L.
Liu, J. Org. Chem. 2005, 70, 7629; b) Y. A. Serguchev, L. F. Lourie, M. V.
Ponomarenko, E. B. Rusanov, Tetrahedron Lett. 2011, 52, 5166.
[18] If pyridine was added at the Selectfluor oxidation stage upon a comple-
tion of the alkyne hydration of 3-en-1-ynamide 1a, this one-pot reac-
tion gave desired 4-hydroxy-2-en-1-amide 4a in 56% yield in addition
to E- and Z-alkenes 3a (23%) and 3a’ (13%).
[7] The 1,2-dioxo reaction on 3-en-1-ynsulfomide was reported in one spe-
cific case; see: R. B. Dateer, K. Pati, R.-S. Liu, Chem. Commun. 2012, 48,
7200.
Received: November 5, 2013
Published online on January 8, 2014
Chem. Eur. J. 2014, 20, 1813 – 1817
www.chemeurj.org
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