Organic Letters
Letter
method gave up to quantitative yields and excellent
diastereoselectivities and was tolerant to both unactivated
and activated alkenes. Furthermore, an alternative intermediate
for the synthesis of lactobacillic acid (6w), could be obtained
with improved diastereoselectivity. More importantly, when
(2) Reviews on methods for the generation of metal carbenes:
a) Jia, M.; Ma, S. New Approaches to the Synthesis of Metal
Carbenes. Angew. Chem., Int. Ed. 2016, 55, 9134−9166. (b) Liu, L.;
Zhang, J. Gold-Catalyzed Transformations of α-Diazocarbonyl
Compounds: Selectivity and Diversity. Chem. Soc. Rev. 2016, 45,
(
5
(
06−516.
employing (R)-6,6′-Br -BINOL, it was possible to obtain, for
2
3) (a) Solorio-Alvarado, C. R.; Wang, Y.; Echavarren, A. M.
the first time in a sequence involving a retro-Buchner reaction,
a product (3g) with 44% ee.
Cyclopropanation with Gold(I) Carbenes by Retro-Buchner Reaction
from Cycloheptatrienes. J. Am. Chem. Soc. 2011, 133, 11952−11955.
In conclusion, we have prepared a new generation of more
reactive cycloheptatrienes, which allowed us to develop two
new systems, based on gold(I) or zinc(II), that perform the
retro-Buchner−cyclopropanation sequence under very mild
conditions. This is the first example of a decarbenation
reaction using zinc(II). Our two new catalytic systems led to a
synthesis of cis-vinylcyclopropanes with wide scope and to the
total synthesis of (±)-lactobacillic acid. Additionally, our first
b) Wang, Y.; McGonigal, P. R.; Herle, B.; Besora, M.; Echavarren, A.
́
(
M. Gold(I) Carbenes by Retro-Buchner Reaction: Generation and
Fate. J. Am. Chem. Soc. 2014, 136, 801−809. (c) Herle, B.; Holstein,
́
P. M.; Echavarren, A. M. Stereoselective cis-Vinylcyclopropanation via
a Gold(I)-Catalyzed Retro-Buchner Reaction under Mild Conditions.
ACS Catal. 2017, 7, 3668−3675.
(4) Wang, Y.; Muratore, M. E.; Rong, Z.; Echavarren, A. M. Formal
(
4 + 1) Cycloaddition of Methylenecyclopropanes with 7-Aryl-1,3,5-
Cycloheptatrienes by Triple Gold(I) Catalysis. Angew. Chem., Int. Ed.
014, 53, 14022−14026.
5) Yin, X.; Mato, M.; Echavarren, A. M. Gold(I)-Catalyzed
results with a system based on BINOL and ZnEt demonstrate
2
2
(
the possibility of developing an enantioselective version of this
transformation. Further investigations along these lines are in
progress.
Synthesis of Indenes and Cyclopentadienes: Access to (±)-Laur-
okamurene B and the Skeletons of the Cycloaurenones and
Dysiherbols. Angew. Chem., Int. Ed. 2017, 56, 14591−14595.
(6) For relevant examples of metal-catalyzed cyclopropanation
reactions, see: (a) Davies, H. M. L.; Bruzinski, P. R.; Lake, D. H.;
Kong, N.; Fall, M. J. Asymmetric Cyclopropanations by Rhodium(II)
N-(Arylsulfonyl)prolinate Catalyzed Decomposition of Vinyldiazo-
methanes in the Presence of Alkenes. J. Am. Chem. Soc. 1996, 118,
ASSOCIATED CONTENT
Supporting Information
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*
S
6
897−6907. (b) Lebel, H.; Marcoux, J.-F.; Molinaro, C.; Charette, A.
B. Stereoselective Cyclopropanation Reactions. Chem. Rev. 2003, 103,
77−1050. (c) Johansson, M. J.; Gorin, D. J.; Staben, S. T.; Toste, F.
Experimental procedures and characterization data for
9
D. Gold(I)-Catalyzed Stereoselective Olefin Cyclopropanation. J. Am.
Chem. Soc. 2005, 127, 18002−18003. (d) Zhu, S.; Perman, J. A.;
Zhang, X. P. Acceptor/Acceptor-Substituted Diazo Reagents for
Carbene Transfers: Cobalt-Catalyzed Asymmetric Z-Cyclopropana-
tion of Alkenes with α-Nitrodiazoacetates. Angew. Chem., Int. Ed.
Cambridge Crystallographic Data Centre, 12 Union Road,
Cambridge CB2 1EZ, UK; fax: +44 1223 336033.
2
008, 47, 8460−8463. (e) Pellissier, H. Recent Developments in
Asymmetric Cyclopropanation. Tetrahedron 2008, 64, 7041−7095.
f) Wang, H.; Guptill, D. M.; Varela-Alvarez, A.; Musaev, D. G.;
(
Davies, H. M. L. Rhodium-Catalyzed Enantioselective Cyclopropa-
nation of Electron-Deficient Alkenes. Chem. Sci. 2013, 4, 2844−2850.
(7) For examples on the use of earth-abundant metals to promote
cyclopropanation reactions, see: (a) Simmons, H. E.; Smith, R. D. A
New Synthesis of Cyclopropanes from Olefins. J. Am. Chem. Soc.
AUTHOR INFORMATION
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1958, 80, 5323−5324. (b) Evans, D. A.; Woerpel, K. A.; Hinman, M.
ORCID
M.; Faul, M. M. Bis(oxazolines) as Chiral Ligands in Metal-Catalyzed
Asymmetric Reactions. Catalytic, Asymmetric Cyclopropanation of
Olefins. J. Am. Chem. Soc. 1991, 113, 726−728. (c) Murai, M.;
Mizuta, C.; Taniguchi, R.; Takai, K. Synthesis of Borylcyclopropanes
by Chromium-Promoted Cyclopropanation of Unactivated Alkenes.
Org. Lett. 2017, 19, 6104−6107. (d) Benoit, G.; Charette, A. B.
Diastereoselective Borocyclopropanation of Allylic Ethers Using a
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
We thank the Agencia Estatal de Investigacion
UE (CTQ2016-75960-P), Severo Ochoa Excellence Acre-
ditation 2014-2018 (SEV-2013-0319 and FPI predoctoral
fellowship to M.M.), the European Research Council
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́
(AEI)/FEDER,
(9) (a) Vicente, R.; Gonzalez, J.; Riesgo, L.; Gonzalez, J.; Lopez, L.
́ ́ ́
A. Catalytic Generation of Zinc Carbenes from Alkynes: Zinc-
Catalyzed Cyclopropanation and Si−H Bond Insertion Reactions.
Angew. Chem., Int. Ed. 2012, 51, 8063−8067. (b) Gonzalez, M. J.;
́
Gonzalez, J.; Lopez, L. A.; Vicente, R. Zinc-Catalyzed Alkene
́ ́
(
1
Advanced Grant No. 321066), the AGAUR (2017 SGR
257), and CERCA Program/Generalitat de Catalunya for
Cyclopropanation through Zinc Vinyl Carbenoids Generated from
Cyclopropenes. Angew. Chem., Int. Ed. 2015, 54, 12139−12143.
financial support. We also thank the ICIQ X-ray Diffraction
unit, the CELLEX-ICIQ HTE unit and Evaristo Villaseco (La
Caixa Summer Fellowship 2016) for preliminary results.
(10) Mayans, J. G.; Armengol-Relats, H.; Calleja, P.; Echavarren, A.
M. Gold(I)-Catalysis for the Synthesis of Terpenoids: From
Intramolecular Cascades to Intermolecular Cycloadditions. Isr. J.
Chem. 2018, 58, 639−658.
(11) (a) Craven, B.; Jeffrey, G. A. The Structure of Lactobacillic
Acid. J. Am. Chem. Soc. 1960, 82, 3858−3860. (b) Coxon, G. D.; Al-
Dulayymi, J. R.; Baird, M. S.; Knobl, S.; Roberts, E.; Minnikin, D. E.
The Synthesis of (11R,12S)-Lactobacillic Acid and its Enantiomer.
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