Rhodium(ii)-catalysed generation of cycloprop-1-en-1-yl ketones and their rearrangement to 5-aryl-2-siloxyfurans

Article abstract of DOI:10.1039/c8cc05623d

Donor-acceptor cyclopropenes formed from enoldiazoketones undergo catalytic rearrangement to 5-aryl-2-siloxyfurans via a novel mechanism that involves a nucleophilic addition of the carbonyl oxygen to the rhodium-activated cyclopropene.

Full text of DOI:10.1039/c8cc05623d

View Article Online
View Journal
ChemComm
Accepted Manuscript
This article can be cited before page numbers have been issued, to do this please use: M. P. Doyle, K. O.
Marichev, Y. Wang, A. Carranco, E. C. Garcia and Z. Yu, Chem. Commun., 2018, DOI:
10.1039/C8CC05623D.
This is an Accepted Manuscript, which has been through the
Volume 52 Number
1 4 January 2016 Pages 1–216
Royal Society of Chemistry peer review process and has been
accepted for publication.
ChemComm
Accepted Manuscripts are published online shortly after
Chemical Communications
www.rsc.org/chemcomm
acceptance, before technical editing, formatting and proof reading.
Using this free service, authors can make their results available
to the community, in citable form, before we publish the edited
article. We will replace this Accepted Manuscript with the edited
and formatted Advance Article as soon as it is available.
You can find more information about Accepted Manuscripts in the
author guidelines.
Please note that technical editing may introduce minor changes
to the text and/or graphics, which may alter content. The journal’s
standard Terms & Conditions and the ethical guidelines, outlined
in our author and reviewer resource centre, still apply. In no
event shall the Royal Society of Chemistry be held responsible
for any errors or omissions in this Accepted Manuscript or any
consequences arising from the use of any information it contains.
ISSN 1359-7345
COMMUNICATION
Marilyn M. Olmstead, Alan L. Balch, Josep M. Poblet, Luis Echegoyenet al.
Reactivity differences of Sc3N@C2n (2n 68 and 80). Synthesis of the
first methanofullerene derivatives of Sc N@D5h-C80
=
3
rsc.li/chemcomm

Please do not adjust margins
Page 1 of 5
ChemComm
View Article Online
DOI: 10.1039/C8CC05623D
Journal Name
COMMUNICATION
Rhodium(II)-catalysed generation of cycloprop-1-en-1-yl ketones
and their rearrangement to 5-aryl-2-siloxyfurans†
Kostiantyn O. Marichev,a Yi Wang,b Alejandra M. Carranco,a Estevan C. Garcia,a Zhi-Xiang Yu*b and
Received 00th January 20xx,
Accepted 00th January 20xx
Michael P. Doyle*a
DOI: 10.1039/x0xx00000x
www.rsc.org/
Previous Work:
Donor−acceptor cyclopropenes formed from enoldiazoketones
Padwa, Garner
R
(a)
(b)
undergo catalytic rearrangement to 5-aryl-2-siloxyfurans via a
novel mechanism that involves a nucleophilic addition of the
carbonyl oxygen to the rhodium-activated cyclopropene.
alkyl
alkyl
R
Rh
2(OAc)4
[ClRh(CO)2]2
O
alkyl
R
O
O
Ph
Ph
Ph
=
R
Me
H,
Furan derivatives are among the most common and readily
available heterocycles,1 and they have broad applications in
organic synthesis2,3 and drug discovery.4 The use of diazo
compounds and metal carbene chemistry has become a
powerful tool for the construction of furan ring.5 First reported
by Garner6a and developed by Padwa,6b diazoketone
compounds have been used to provide access to furans
through initial catalytic cyclopropenation of alkynes with
subsequent catalytic rearrangement of the cycloprop-2-en-1-yl
ketones to furans. The metal catalyst Rh(I) vs. Rh(II) defined
the selectivity of the reaction (Scheme 1a);6b,c use of the Rh(I)-
catalyst led to 2,3,5-trisubstituted furans, while the Rh(II)-
catalyst afforded 2,3,4-trisubstituted furans predominantly.
Ma
C4H9
C4H9
EtO2C
EtO2C
MLn
=
MLn
O
C4H9
M
=
CO2Et
M
Cu(I),
Pd(II),
Ru(III), Rh(III)
O
O
Me
Me
Cu(II)
Me
This Work:
OSi
O
(c)
3
1
2
Ar
4
RhLn
fast
RhLn
RhLn
fast
-
N2
OSi
O
RhLn
catalytic
4
3
O
1
2
2
catalyst free
3
Ar
1
SiO
4
OSi
1
Ar
2
3
N2
-
N2
O
Ar
4
very
slow
Single
regioisomer
Scheme 1 Divergent outcomes of metal-catalysed rearrangement of
cycloprop-2-en-1-yl vs. cycloprop-1-en-1-yl ketones.
Ma and co-workers subsequently reported
a catalyst-
controlled divergent ring-opening cycloisomerisation of
cycloprop-2-en-1-yl carboxylates (Scheme 1b).7a The same
regioselectivity (2,3,5- vs. 2,3,4-) as from the Rh(I)-catalyst
(Scheme 1a) was observed with Pd(II)-, Ru(III)-, or Rh(III)-
catalysts, and the same regioselectivity as Rh(II) was observed
with Cu(I) or Cu(II). The reaction scope was also expanded to
We previously reported that enoldiazoacetates and
enoldiazoacetamides undergo dinitrogen extrusion thermally
and with selected catalysts, to form donor−acceptor
cyclopropenes quantitatively under mild conditions.8 These
cyclopropene products are stable at room temperature, but
they have proven to be effective metal carbene precursors
with appropriate catalysts,9 and they are reactive
dipolarophiles for [3+2] cycloaddition reactions.10 In our
efforts to broaden the scope of enoldiazocarbonyl compounds
and their reactions, we have prepared enoldiazoketones and
found that they expectedly extrude dinitrogen to form the
corresponding cycloprop-1-en-1-yl ketones, but these products
then undergo a surprising catalytic skeleton rearrangement to
furans under mild conditions and in high yields (Scheme 1c).
cycloprop-2-en-1-yl
dicarboxylates,
which
afforded
methoxyfurans.7b The Lewis acid BF3
∙
Et2O was also used for the
ring-opening cycloisomerisation of spiro-cyclopropenes and
the construction of fused furans (2,3,5-selectivity).7c 2,3,4-
Selectivity in this case was achieved with the use of copper(II)
triflate.
a.Department of Chemistry, The University of Texas at San Antonio, San Antonio,
Texas 78249, USA. E-mail: michael.doyle@utsa.edu
b.Beijing National Laboratory for Molecular Sciences (BNLMS), Key Laboratory of
Bioorganic Chemistry and Molecular Engineering of Ministry of Education, College
of Chemistry, Peking University, Beijing 100871, China. E-mail: yuzx@pku.edu.cn
†
Electronic supplementary information (ESI) available: Experimental procedures,
NMR spectra of compounds and computational details. See DOI:
10.1039/x0xx00000x
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 1
Please do not adjust margins

ChemComm
Please do not adjust margins
Page 2 of 5
Journal Name
COMMUNICATION
NaH
EtOAc
1)
2)
O
O
O
OSi
Table 1 Substrate scope for the synthesis of 5-aryl-2-siloxyfurans 6
View Article Online
O
O
O
p
ABSA
NEt3
Si
OTf
DOI: 10.1039/C8CC05623D
Ar
Me
Ar
NEt3
DCM, 1 h
Ar
Me
Ar
Me
THF, 12 h
OSi
O
0.5 mol%
MeCN, 12 h
N2
N2
Rh
2(oct)4
OSi
Ar
1
2
3
4
O
-
N2
Ar
N2
r.t., 6 h
DCM,
Scheme 2 Synthesis of enoldiazoketones
4
.
4
6a
OTMS
O
OTBS
OTIPS
O
O
Enoldiazoketones
from commercially available acetophenones
in the previously reported conversions to donor−acceptor
cyclopropenes, 3-(tert-butyldimethylsilyloxy)-2-diazo-3-
4
were prepared in a 3-step procedure
1
(Scheme 2). As
6bd
93%
6a
91%b
6c
c
77%
(85%)
(65%)
(89%)
OTBS
OTBS
OTBS
butenoylbenzene (4a, Ar = Ph, Si = TBS) was treated with a
catalytic amount of dirhodium(II) tetrakis(octanoate)
[Rh2(oct)4] in dichloromethane at room temperature.
O
O
O
Me
F3C
MeO
6d
85%
6f
6e
88%
92%
O
(78%)
(84%)
(85%)
Dinitrogen
butyldimethylsilyloxy)-1-benzoylcyclopropene (5a) was formed
along with 2-(tert-butyldimethylsilyloxy)-5-phenylfuran (6a
evolution
was
rapid,
and
2-(tert-
OTBS
OTBS
OTBS
)
O
O
(eqn (1)) whose yield increased at the expense of 5a in the
presence of the dirhodium catalyst. In the absence of the
catalyst, cyclopropene 5a did not rearrange to furan 6a, but 5a
was slowly formed from 4a even at room temperature.
Br
F
Cl
6i
6g
90%
6h
87%
84%
(78%)
(84%)
(83%)
OTBS
OTBS
OTBS
O
O
O
MeO
O
OTBS
S
O
Rh
2(oct)4
6j
6k
76%
6l
+
OTBS
Ph
OTBS
(1)
82%
Ph
87%
(75%)
(72%)
(82%)
DCM
O
N2
Ph
MeO
F
Cl
OTBS
4a
5a
6a
OTBS
OTBS
O
O
O
Furthermore, since both donor−acceptor cyclopropene and
6m
6n
75%
6o
74%
(70%)
furan formation occur in sequence, the overall transformation
can be initiated from the enoldiazo compound. In view of the
novelty of this transformation, which takes place through
skeleton rearrangement and hydrogen migration, as well as
the potential utility of the products, we further investigated
this transformation.
95%
(92%)
(68%)
aSynthesis of furans
6
was carried out on
enoldiazoketones 4. Yield was determined by the H NMR spectral analysis
a
1.0 mmol scale of
b
1
of the reaction mixture with 1,3,5-trimethoxybenzene as an internal
c
standard. Isolated yield after flash chromatography. dReaction time was
12 h.
As with Rh2(oct)4, a catalytic amount of Cu(MeCN)4BF4
generates the donor−acceptor cyclopropene 5a rapidly, but
use of this catalyst does not lead to the furan ring. Alternative
catalysts, [Ru(p-cymene)Cl2]2, Pd(PhCN)2Cl2 and dirhodium(II)
caprolactamate [Rh2(cap)4], had limited reactivity for the
dinitrogen extrusion step and formed the furan ring in yields
lower than 30% under identical conditions as those used for
Rh2(oct)4 and Cu(MeCN)4BF4 catalysis.11 Among rhodium(II)
carboxylates, Rh2(oct)4 was found to be the most efficient
catalyst for furan formation, and 0.5 mol% was the optimal
catalyst loading. Although dirhodium(II) tetraacetate
Having the optimal catalyst in hand we explored the
substrate scope of this one-pot transformation of
enoldiazoketones
4 to 5-aryl-2-siloxyfurans 6 (Table 1). Use of
the TBS protecting group was preferred because of its relative
stability. Although the TIPS-protected furan 6b was also
formed in very high yield (93%), its reaction time was double
of that for TBS-protected substrate. The introduction of
electron-donating or -withdrawing substituents at the para
position of the aromatic ring did not affect reactivity (6d−i).
Substrates with 2-thiophenyl and 3-methoxyphenyl
substituents were also tolerant and afforded the target furans
6j and 6l in yields higher than 80%. 1-Naphtyl-, 2-chlorophenyl-
[Rh2(OAc)4]
and
bis[rhodium(α,α,α’,α’-tetramethyl-1,3-
benzenedipropionic acid)] [Rh2(esp)2] afforded furan in high
yields, the rates of their reactions were slower. The presence
of electron-deficient or sterically encumbered substituents in
Rh(II) carboxylates {dirhodium(II) tetrakis(perfluorobutyrate)
[Rh2(pfb)4] and dirhodium(II) tetrakis(triphenylacetate)
[Rh2(tpa)4]} does not facilitate furan formation, although they
generated cyclopropene 5a very rapidly. Treatment of 5a with
Lewis acids like AgBF4 and Sc(OTf)3 facilitated the formation of
furan, but also led to TBS removal to form 5-phenylfuran-
2(3H)-one (7a).
and 2-methoxyphenylfurans 6k
yields (75% in average). The highest yield (95%) was achieved
on 2-fluorophenyl substrate 4m, even higher than with 4a
Diazoacetyl analogues of formed the corresponding
, 6n, 6o were obtained in lower
.
4
cyclopropenes rapidly and in high yields, but produced only
minor amounts of the corresponding furans in complex
product mixtures with the same catalyst at or above room
temperature.
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 2
Please do not adjust margins

Page 3 of 5
ChemComm
Please do not adjust margins
Journal Name
COMMUNICATION
TMSO
O
Δ
View Article Online
DOI: 10.1039/C8CC05623D
mol–
1
G
=
(kcal
Rh
)
δ
M
TMSO
2(OCHO)4
Ph
δ
δ
δ
δ
O
TMSO
M
O
N2
TMSO
O
Ph
Ph
δ
TS1
18.1
M
Ph
δ
δ
M
N2
TMSO
TS3
M
O
A
TS4
O
TMSO
Ph
M
10.0
8.4
9.3
9.1
Ph
D
H
M
N2
M
0.0
H
TMSO
O
4c
TS2
TS5
–5.1
Ph
TMSO
O
–4.6
–10.8
M
Ph
B
–14.3
–27.9
N2
TMSO
O
C
M
–58.5
E
TMSO
F
O
Ph
–61.5
O
TMSO
Ph
O
TMSO
M
Ph
M
6c
Ph
O
TMSO
Ph
M
M
Fig. 1 Gibbs energy profile for the reaction of substrate 4c under the catalysis of rhodium(II) formate. Computed at the B3LYP/def2-SVP level.13
Furan formation from donor−acceptor cyclopropenes
(Scheme 1c) is quite different from that previously developed
(Scheme 1a,b). To shed some light on the reaction mechansim,
we performed DFT calculations on the reaction of substrate 4c
under the catalysis of a model catalyst, rhodium(II) formate
(Fig. 1).12 The reaction begins with dinitrogen extrusion of the
observed in our experiments is different from the preference
for the 2,4-selectivity in the rearrangement of 3-
acylcyclopropene under Rh(II) catalysis (Scheme 1a, right).6
This methodology provides convenient access to 5-aryl-2-
siloxyfurans, which are of considerable value in nucleophilic
and electrophilic reactions. Upon loss of the silyl group, 6a
readily forms 5-phenylfuran-2(3H)-one (7a) (Scheme 3). Furan-
rhodium−substrate complex
generating a rhodium carbene intermediate
bond formation takes place via
electrocyclisation transition state TS2
A
via transition state TS1
. Then, a C−C
2π-disrotatory
leading to
,
B
2(3H)-ones
7 are analogues of butenolides − a class of
a
,
compounds16 the structural unit of which is found in numerous
natural products.17 Interestingly, 2-siloxyfurans, which do not
a
rhodium−cyclopropene complex
(<10 kcal mol−1) between
and
such an interconversion. Subsequently,
C. The small energy barrier
B
C
indicates the reversibility of have a substituent at position 5, normally react with
C
dissociates to give
R1
cyclopropene 5c or undergoes an intramolecular nucleophilic
addition of the carbonyl oxygen to the rhodium-activated
cyclopropene via transition state TS3. The Gibbs energy of
activation for such a C−O bond formation step is 24.3 kcal
R2
O
O
Ph
O
a
8a R1 R2 Me
O
=
,
(90%)
mol−1. The resulting zwitterionic intermediate
undergoes a rapid ring expansion via transition state TS4
leading to the formation of a vinylrhodium intermediate
D
then
b
R1
R2
2.5
H
2
8b R1 Ph, R
O
=
=
Ph
(94%)
c
(82%)
8c R1 Ph, R
Me
2
=
=
,
.
TBAF
equiv.
NEt3
7a
(98%)
DCM
r.t., 30 min
E
Ph
O
5 mol%
Sc(OTf)3
1.5
1.2
HSiEt
equiv.
3
Such a process should better be regarded as a ring opening of
cyclopropyl silyl ether followed by electronic reorganisation,
rather than a 4π electrocyclic ring opening, which requires a
geometrically unrealisable conrotatory transition state. After
that, a suprafacial [1,5] sigmatropic hydrogen shift occurs,14
OTBS
PhCHO
r.t., 2 h
equiv.
O
Ph
O
DCM,
Ph
6a
9
(80%)
1.5
2.5
equiv.
equiv.
BnNH2
DCM
Z
20 mol% BF3 Et2O
THF, r.t., 6 h
r.t., 24 h
O
O
Z
O
H
H
N
HO
HO
Ph
furnishing a rhodium−furan complex
F. Finally, the dissociation
+
Ph
Bn
H
Ph
Z
O
of gives the catalyst and the furan product 6c. Removing the
F
12
11
10
(96%)
siloxy group or replacing the benzoyl group by an acetyl group
leads to a significant increase in the overall Gibbs energy of
activation,12 demonstrating the important role of electron-
donating siloxy and aryl groups on the stabilisation of the
intermediates and transition states along the reaction path,
which facilitates the reaction to occur.
We have also considered an alternative mechanism in
which the initially formed donor−acceptor cyclopropene 4c
undergoes a [1,3] sigmatropic hydrogen shift to generate a 3-
5 mol% PTSA H2O
THF, r.t., 30 min
a
:
=
=
=
:
Z
CN:
11a 12a 3:2
70%,
=
b Z COOMe: 63%, 11b 12b 1:1
-
H2O
Ph
OH
Z
13
a
=
Z
CN: 96%;
d
=
b Z COOMe: >99%
aReaction was carried out in acetone at 22 °C, reaction time 12 h. b1.2 Equiv.
c
of benzaldehyde used, DCM, 22 °C, 4 h. 1.5 Equiv. of acetophenone used,
d
acylcyclopropene and then completes the furan synthesis DCE, 80 °C, 16 h. Complete aromatisation occurred at r.t. in 24 h without
(Scheme 1a). However, it is unlikely to take place, not only
the use of acid.
because of the extremely high Gibbs energy of activation for
Scheme 3 Chemical transformations of 5-phenyl-2-siloxyfuran 6a.
the symmetry-forbidden suprafacial [1,3] sigmatropic
hydrogen shift,15 but also because the exclusive 2,5-selectivity
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 3
Please do not adjust margins

ChemComm
Please do not adjust margins
Page 4 of 5
Journal Name
COMMUNICATION
electrophiles to form furan-2(5H)-ones.18 However, 5-aryl-
substituted 2-siloxyfurans form 3-substituted 5-arylfuran-
2(3H)-ones exclusively as the thermodynamic product.
Compound 6a reacts with acetone and benzaldehyde at room
temperature in the presence of triethylamine to form 5-
Heterocycles in Natural Product Synthesis, 2011, Wiley-VCH
View Article Online
Verlag GmbH & Co.; (c) X.-F. Wu, TraDnsOitI:io10n.1m03e9t/aCl8CcaCt0a5ly62ze3Dd
furan synthesis, 1st edition from Transition metal catalyzed
heterocycles synthesis series, 2015, Elsevier Publ.
3
For recent examples of transition metal-catalysed synthesis
of furans, see: (a) Y. Wu, Z. Huang, Y. Luo, D. Liu, Y. Deng, H.
Yi, J.-Fu. Lee, C.-W. Pao, J.-L. Chen and A. Lei, Org. Lett.,
2017, 19, 2330; (b) A. Dey, M. A. Ali, S. Jana and A. Hajra, J.
Org. Chem., 2017, 82, 4812; (c) K. B. Hamal and Wesley A.
Chalifoux, J. Org. Chem., 2017, 82, 12920; (d) R. Parnes, H.
Reiss and D. Pappo, J. Org. Chem., 2018, 83, 723; (e) M.
Miao, H. Xu, M. Jin, Z. Chen, J. Xu and H. Ren, Org. Lett.,
2018, 20, 3096.
phenyl-(3-ylidene)furan-2(3H)-ones 8a,b in very high yields
(Scheme 3). The reaction of 6a with acetophenone required a
higher temperature to achieve a good yield of 5-phenyl-(3-
ylidene)furan-2(3H)-one 8c (82%) that was formed with
exclusive E-selectivity. Highly regioselective one-pot coupling-
hydrogenation of 6a was carried out using benzaldehyde and
triethylsilane. Upon reaction with benzylamine, furan 6a forms
ring opened product 10 in 96% yield. Reaction of 6a with
acrylonitrile or methyl acrylate formed Diels−Alder
cycloadducts and subsequent hydrolytic ring opening gave 11
and 12 as a mixture of diastereomers in moderate yields.
Nitriles 11a and 12a were stable at room temperature,
whereas esters 11b and 12b underwent loss of water and
quantitative aromatisation to form 2-substituted 4-
phenylphenol 13b, a compound that was previously accessible
only by cross-coupling reactions.19 Analogous 2-cyano-4-
phenylphenol 13a was obtained in 96% yield from a mixture of
11a and 12a by treatment with a catalytic amount of p-
toluenesulfonic acid (PTSA) at room temperature (Scheme 3).
In summary, we have discovered a new mechanistic
pathway for the formation of 2,5-disubstituted furans from
cycloprop-1-en-1-yl ketones generated from silyl-protected
enoldiazoketones. The regioselectivity of the process is totally
different from those formed from cycloprop-2-en-1-yl ketones.
The rearrangement is catalyst-dependent with rhodium(II)
carboxylates being the most efficient. DFT calculations have
been performed to understand the reaction mechanism,
showing that the electron-donating siloxy and aryl groups are
both essential to facilitate the reaction. Synthesized furans are
good sources of valuable furan-2(3H)-ones. Unlike the
reported unsubstituted 2-siloxyfurans or 5-alkyl-2-siloxyfurans,
our 5-aryl-2-siloxyfurans underwent coupling reactions with
electrophiles at position 3 selectively.
4
5
(a) É. Lukevits and L. Demicheva, Chem. Heterocycl. Compd.,
1993, 29, 243; (b) J. B. Sperry and D. L. Wright, Curr. Opin.
Drug Discovery Dev., 2005,
M. Banerjee, Int. J. Rev. Life. Sci., 2012,
(a) A. Padwa, Molecules, 2001, , 1; (b) T. Johnson, D. R.
Cheshire, M. J. Stocks and Vicky T. Thurston, Synlett, 2001,
8
, 723; (c) R. Banerjee, K. HKS and
2
, 7.
6
5
,
646; (c) H. M. L. Davies, W. R. Cantrell Jr., K. R. Romines and
J. S. Baum, Synthesis of furans via rhodium(II) acetate-
catalyzed reaction of acetylenes with α‐diazocarbonyls: ethyl
2-methyl-5-phenyl-3-furancarboxylate, Organic Syntheses,
2002, John Wiley & Sons, Inc.; (d) X. Cui, X. Xu, L. Wojtas, M.
M. Kim and X. P. Zhang, J. Am. Chem. Soc., 2012, 134, 19981;
(e) M. L. Hossain, F. Ye, Y. Zhang and J. Wang, Tetrahedron,
2014, 70, 6957; (f) S. Muthusamy and M. Sivaguru, Org. Lett.,
2014, 16, 4248; (g) Y. Huang, X. Li, Y. Yu, C. Zhu, W. Wu and
H. Jiang, J. Org. Chem., 2016, 81, 5014; (h) W. W. Tan and N.
Yoshikai, J. Org. Chem., 2016, 81, 5566.
6
7
(a) P. Garner and S. Ramakanth, J. Org. Chem., 1987, 52,
2631; (b) A. Padwa, J. M. Kassir and S. L. Xu, J. Org. Chem.,
1991, 56, 6971; (c) A. Padwa, J. M. Kassir and S. L. Xu, J. Org.
Chem., 1997, 62, 1642.
(a) S. Ma and J. Zhang, J. Am. Chem. Soc., 2003, 125, 12386;
(b) J. Chen and S. Ma, Chem. − Asian J., 2010, 5, 2415; (c) J.
Gong, Z. Zhao, F. Zhang, S. Wu, G. Yan, Y. Quan and B. Ma,
Org. Lett., 2014, 16, 5524; (d) G. Huang and Y. Xia, ACS
Catal., 2015, 5, 859.
8
9
Y. Deng, C. Jing and M. P. Doyle, Chem. Commun., 2015, 51,
12924.
Y. Deng, C. Jing, H. Arman and M. P. Doyle, Organometallics,
2016, 35, 3413.
10 (a) X. Xu, D. Shabashov, P. Y. Zavalij and M. P. Doyle, Org.
Lett., 2012, 14, 800; (b) X. Xu, D. Shabashov, P. Y. Zavalij and
M. P. Doyle, J. Org. Chem., 2012, 77, 5313; (c) X. Xu, P. Y.
Zavalij and M. P. Doyle, J. Am. Chem. Soc., 2013, 135, 12439.
We acknowledge U.S. National Science Foundation (CHE-
1212446) and the National Natural Science Foundation of
China (21232001) for supporting this research. The NMR
spectrometer used in this research was supported by a grant
from the U.S. National Science Foundation (1625963).
11 See the ESI
12 See the ESI
†
†
for the details on metal-catalyst screening.
for computational details.
13 (a) C. Lee, W. Yang and R. G. Parr, Phys. Rev. B, 1988, 37, 785;
(b) A. D. Becke, J. Chem. Phys., 1993, 98, 5648; (c) F.
Weigend and R. Ahlrichs, Phys. Chem. Chem. Phys., 2005,
3297.
14 F. Jensen, Chem. Phys. Lett., 1989, 161, 368.
7,
Conflicts of interest
There are no conflicts to declare.
15 For a related [1,5] sigmatropic alkyl shift, see: G.-Q. Chen, X.-
N. Zhang, Y. Wei, X.-Y. Tang and M. Shi, Angew. Chem., Int.
Ed., 2014, 53, 8492.
̃
́
16 B. Mao, M. Fananas-Mastral and B. L. Feringa, Chem. Rev.,
2017, 117, 10502.
17 J. C. Slaughter, Biol. Rev., 1999, 74, 259.
18 X. Li, M. Lu, Y. Dong, W. Wu, Q. Qian, J. Ye and D. J. Dixon,
Notes and references
Nature Commun., 2014,
5, 4479.
1
(a) V. M. Chernyshev, O. A. Kravchenko and V. P. Ananikov,
Russ. Chem. Rev., 2017, 86, 357; (b) Z. Zhang and G. W.
Huber, Chem. Soc. Rev., 2018, 47, 1351.
19 B. Schmidt and F. Hölter, Org. Biomol. Chem., 2011,
9
, 4914.
2
(a) M. Sainsbury, Five-membered heterocycles containing
one heteroatom: Pyrrole, furan and thiophene, E. W. Abel
ed., Heterocyclic Chemistry, 2001, RSC Publ.; (b) A. Boto and
L. Alvarez, Chapter 4: Furan and its derivatives from
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 4
Please do not adjust margins

Page 5 of 5
ChemComm
View Article Online
DOI: 10.1039/C8CC05623D
A new mechanistic pathway for the formation of 2,5-
disubstituted furans from cycloprop-1-en-1-yl ketones
generated from silyl-protected enoldiazoketones.