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Catalytic Cleavage of C(sp2)−C(sp2) Bonds with Rh-Carbynoids
Zhaofeng Wang,‡ Liyin Jiang,‡ Pau Sarró,‡ and Marcos G. Suero*
Institute of Chemical Research of Catalonia (ICIQ), The Barcelona Institute of Science and Technology, Països Catalans 16, 43007
Tarragona, Spain

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S
* Supporting Information

ABSTRACT: We report a catalytic strategy that generates rhodium-carbynoids by selective diazo activation of
designed carbyne sources. We found that rhodiumcarbynoid species provoke C(sp2)−C(sp2) bond scission
in alkenes by inserting a monovalent carbon unit between
both sp2-hybridized carbons. This skeletal remodeling
process accesses synthetically useful allyl cation intermediates that conduct to valuable allylic building blocks
upon nucleophile attack. Our results rely on the formation
of cyclopropyl-I(III) intermediates able to undergo electrocyclic ring-opening, following the Woodward−Hoﬀmann−DePuy rules.

F

or more than half a century, the discovery of new metal−
carbon bond-forming strategies has been cornerstone in
the development of transition-metal catalysis.1 The catalytic
generation of organometallic species with metal−carbon
single/double bonds, such as metal−L (L = alkyl, alkenyl,
alkynyl, aryl) or metal−carbene (metalL) is widely used in
reaction discovery and development. However, while metalcarbynes, the organometallic species with a metal−carbon
triple bond (metalL),2 have been key catalysts in alkyne
metathesis,3 their catalytic generation and general application
in catalytic carbyne transfer has been largely unexplored,
mainly due to the lack of suitable monovalent carbon sources
(Figure 1A).4 Surprisingly, methodologies circumventing this
problem by generating metal-carbynoids as equivalent reactive
species of metal-carbynes, have not been reported.
Recently, our group demonstrated the ﬁrst catalytic
generation of diazomethyl radicals [N2C(•)R] as carbyne
equivalents by means of photoredox catalysis.5,6 This work
highlighted the under-appreciated ability of neutral carbynes to
form three new bonds7 and provided the fundaments of an
“assembly-point” coupling for chiral center construction,
through a CH bond diazomethylation reaction in aromatic
feedstocks and drug molecules. Key on this work was the use of
stable carbyne sources decorated bonds with a hypervalent
iodine moiety [I(III)(Ar)(OTf)] and a diazo functionality
(=N2).8 We recently questioned whether well-known dirhodium catalysts in diazo activation9 might generate Rhcarbynoids as I(III)-substituted Rh-carbenes (Figure 1B).
Considering the outstanding leaving group ability of the I(III)
moiety10 and weakness of the hypervalent bond, we anticipated
that the electrophilic carbon center of the Rh-carbynoid would
emulate the carbene/carbocation behavior of a monovalent
cationic carbyne (:+CR), and enable a novel route to allylic
© 2019 American Chemical Society

Figure 1. Catalytic cleavage of C(sp2)C(sp2) bonds with Rhcarbynoids.

cations from alkenes, by the insertion of the monovalent
carbon unit in the C(sp2)C(sp2) bond (Figure 1B).
Such a process, that involves a σ- and π-bond activation of
the alkene double bond and uses both sp2-hybridized carbons
as functional groups, would be a rare example of a catalytic
cleavage of strong double CC bonds (BDE, H2CCH2 =
174.1 kcal/mol), besides processes of metathesis11,12 or
rearrangements.13 It would also represent a new way for
catalytic skeletal remodeling, complementing “cut and sew”
and deconstructive transformations based on single CC
bond functionalization.14 Notably, accessing allyl intermediates
by C(sp 2 )C(sp 2 ) bond cleavage would represent a
complementary, but clearly diﬀerent strategy, to the wellestablished transition-metal-catalyzed allylations15 or allylic
CH bond functionalizations.16 Herein, we disclose the
successful development of a Rh-catalyzed carbyne transfer
platform for the catalytic cleavage of C(sp2)C(sp2) bonds
that provides a novel route to allylic building blocks.
Received: August 9, 2019
Published: September 12, 2019
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We envisioned that the selective diazo activation of reagent
2 with a paddlewheel dirhodium complex L4Rh2 would
conduct to a highly electrophilic Rh-carbynoid 3 (Scheme
1). The latter species would cyclopropanate an alkene and

Table 1. Optimization Studies

Scheme 1. Mechanistic Hypothesis

a

Performed with cyclohexene (0.5 mmol, 5 equiv), reagent 2a (0.1
mmol, 1 equiv), CH2Cl2 (0.1 M) and nucleophile (3 equiv). boct =
octanoate. Adc = 1-adamantylcarboxylate. esp = α,α,α′,α′-tetramethy1,3-benzenedipropanoate. cYields are reported on the basis of 1H
NMR analysis using anisole as internal standard. dReaction carried
out with 1 equiv of 1a. 30% of 1a was detected.

generate a transient cyclopropyl-I(III) intermediate 4. In
analogy to the well-known ring-opening of cyclopropyl
tosylates or cyclopropyl bromides with silver salts,17 4 would
open in concert with the departure of the I(III) leaving group
through a disrotatory mode, following the Woodward−
Hoﬀmann−DePuy rules.18 This process would lead to a
putative allylic cation 5 able to provide the desired allylic
product 6 by nucleophile attack, or diene 7 by proton
elimination.
Initial successful results were found when a solution of 2a in
dichloromethane was added to cyclohexene (5 equiv) and
Rh2(Oct)4 (1 mol %) at −50 °C during 1 h. Then, Bu4NBr (3
equiv) was added at −50 °C and the resulting mixture stirred
for 60 min. With this protocol allyl bromide 6a was obtained in
a promising 17% yield (Table 1, entry 1). The use of the more
sterically demanding catalysts Rh2(Adc)2 or Rh2(esp)2 (Du
Bois catalyst)19 provided signiﬁcantly superior levels of
eﬃciency of 6a (30−48% yield, respectively) and the
formation of diene 7a in less than 10% yield (entries 2 and
3). After identifying Rh2(esp)2 as the most promising catalyst,
we questioned whether the nature of reagent 2 could have a
substantial impact in the eﬃciency of the process. First, we
realized that the pseudocyclic structure of reagent 2a was
crucial for enabling the synthesis of allylic bromide 6a. No
conversion to 6a was observed for cyclic reagent 2b (entry 4)
and very poor yields were obtained for the linear analogue 2b
(entry 5). Finally, we were pleased to ﬁnd that pseudocyclic
reagents 2d,e with BF4 and PF6 counterions, dramatically
improved the eﬃciency of the C(sp2)C(sp2) cleaving
process (entries 6 and 7). We also appreciated that excess of
alkene 1a was needed to reach good eﬃciency. An experiment
carried out with equimolecular ratio of 1a and 2e, showed a
poorer yield for 6a/7a (entry 8, 45/7% yield) and 30% of
cyclohexene was detected. This might suggests that such excess
ensures full conversion in the ligand transfer event between the

corresponding Rh-carbynoid 3 and cyclohexene, preventing
the evolution of 3 through undesired pathways.20 The use of
Bu4PBr or TMSBr as a bromide source did not provide better
results (entries 9 and 10).21
Having the optimized conditions in hand, we evaluated the
nucleophile scope by using cyclohexene and reagent 2e (Table
2A). We were delighted to see that our methodology worked
well for a broad and diverse range of simple nucleophiles that
created: (i) carbon−halogen bonds with Bu4NBr (6a), and
Et3N·3HF (6b); (ii) carbon−oxygen bonds with methanol
(6c), tetrabutylammonium acetate (6d), water (6e), and
TEMPO (6f); (iii) carbon−sulfur bonds with thiols (6g); and
(iv) carbon−nitrogen bonds with Bu4NSCN (6h), tert-butyl
carbamate (6i), Bu4NN3 (6j), and 4-methoxyaniline (6k).
Moreover, our strategy permitted the use of a diverse range of
carbon nucleophiles, enabling CH arylation processes with
electron-rich arenes (6l−n) or heterocycles (6o), allylation
with allyl-SnBu3 (6p), alkylation with the trimethylsilyl enol
ether derived from acetophenone (6q), or amidation with the
combination of tert-butylisocyanide, pyridine oxide and water
(6r). It is noteworthy the high degree of complexity
introduced in the constructive cleaving process: one new
single CC bond and one new double CC bond are
created, in addition to the formation of a chiral center at one of
the sp2-hybridized carbons of cyclohexene using some of the
most simple and abundant nucleophiles.
Next, we wondered whether we could convert oleﬁn
petrochemical feedstocks and styrenes into allylic building
blocks. We embarked on this journey by ﬁrst evaluating
ethylene, the most widely produced chemical feedstock by the
petrochemical industry with an annual global production above
134 million tones. We were glad to ﬁnd that our methodology
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Journal of the American Chemical Society
Table 2. Scope of the Catalytic Cleavage of C(sp2)C(sp2) Bonds for Allylic Building Block Synthesisa

a
Performed with alkene (1.0 mmol, 5 equiv), reagent 2e (0.2 mmol, 1 equiv), CH2Cl2 (0.1 M) and nucleophile (3−20 equiv). Yield of parentheses
are of dienes 7. See Supporting Information for experimental details.

was able to convert ethylene into allyl bromide 6s with high
eﬃciency (Table 2B). To the best of our knowledge, this is the
ﬁrst example of a catalytic constructive scission in ethylene that
provokes the conversion to an allyl bromide. This result can be
explained by the initial formation of intermediate 8,

subsequent electrocyclic ring-opening and bromide attack to
the resulting allyl cation 9. Also, our process worked well with
propylene, the most important feedstock of the α-oleﬁn family.
In this case, allyl bromide 6t was obtained with a 14:1 linear/
branched selectivity and in 89% yield (Table 2B). The 4:1
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Scheme 2. C(sp2)C(sp2) Bond Cleavage Enables Cyclizationsa

Reaction conditions: 1 mol % Rh2(esp)2, −50 °C, 1 h then to rt, 3 h, CH2Cl2.

a

of an analogue of 10 having both Ph ring and I(III) moiety in
syn disposition.
The strategic advantage of inserting a monovalent carbon
unit into a C(sp2)C(sp2) bond was further exploited to
induce cyclization reactions (Scheme 2). Simple alkenes with a
remote alcohol nucleophile and natural product derivatives
were selectively cyclized with moderate to excellent yields
(14−18, 52−91% yield). On the basis of the previous results,
we postulate that the cyclization reactions involve the selective
catalytic generation of carbocations 19−21 that selectively
evolve to the heterocyclic products through exo (19, 20, 22)
and endo cyclizations (21).
Finally, we wanted to provide evidence of cyclopropyl
hypervalent iodine intermediates 4, despite the well-known
thermodynamic instability of alkyl-I(III) species.23 Initial eﬀorts
toward the isolation of cyclopropyl-I(III) intermediates from
mono (styrene) and disubstituted oleﬁns (cyclohexene) at −50
°C were unsuccessful. It is known that the electrocyclic ringopening in substituted cyclopropyl tosylates is kinetically
favored over the nonsubstituted derivatives.17 With this
information, we hoped that trapping the corresponding
cyclopropyl-I(III) intermediate derived from ethylene could be
more feasible. By using reagent 2f and Rh2(Adc)4 as a catalyst,
we were glad to isolate at room temperature cyclopropyl-I(III)
compound 23 as a relative stable white solid in 56% yield,
whose structure was conﬁrmed by single-crystal X-ray
diﬀraction analysis (Scheme 3). To the best of our knowledge,
this is the ﬁrst isolable alkyl-I(III) compound of this class, and
we postulate this result may inspire future endeavors for the
design of novel hypervalent alkyl-I(III) reagents. As a control
experiment, we demonstrated that the treatment of 23 with
Bu4NBr gave the expected allyl bromide 24 with high eﬃciency
(Scheme 3).
In summary, we have developed a Rh-catalyzed carbyne
transfer platform for the catalytic cleavage of C(sp2)C(sp2)
bonds. We have demonstrated that this process is able to
convert feedstock alkenes, styrenes and a broad diversity of

selectivity observed in favor for the Z isomer in the linear
isomer is suggesting the preferential formation of 10, where
substituent R and I(III) moiety are in relative syn disposition.
Subsequently, the electrocyclic ring-opening by disrotatory
mode would conduct to 11, (the R group rotates inwardly),
which undergoes bromide attack at the less hindered
electrophilic carbon site (α position). Moreover, while similar
eﬃciencies and selectivities were obtained for 1-butene (6u)
and 1-hexene (6v), the reaction with styrene provided
excellent yield and selectivities in favor of the linear isomer
6w. On the other hand, we anticipated that 1,2-disubstituted
alkenes such as (E)-2-butene and (E)-β-methyl-styrene would
potentially challenge our methodology: the formation of 12
and subsequent electrocyclic ring-opening, would provide a
trisubstituted allyl cation 13 with two similar electrophilic sites
(α and α′ position), and mixtures of allyl bromides could be
formed (Table 2B). However, we were delighted to ﬁnd that
the reaction gave allyl bromides 6x and 6y with a high regioand stereoselectivity. Furthermore, our insertion reaction
enabled ring expansion in larger rings, including cycloheptene
(6z), cyclooctene (6aa) and cyclododecene (6ab).
An important feature of our C(sp2)C(sp2) bond cleavage
process is the ability to transform alkenes into others with a
higher substitution. We believed that we could provide a new
approach for the synthesis of synthetic challenging tetrasubstituted oleﬁns, which lack a general synthesis approach and
are present in drug molecules and molecular motors.22 Based
on previous results, we anticipated that 1,1-disubstituted
oleﬁns, which are commercially available or easy to make
from ketones by ylide oleﬁnation, could be suitable substrates
to reach the tetrasubstituted oleﬁn core. We were pleased to
ﬁnd that commercial methylenecyclohexane and α-methylstyrene could be eﬃciently converted into tetra-substituted oleﬁns
6ac and 6ad by using Bu 4NO 2 CPh and Bu 4NN 3 as
nucleophile, respectively (Table 2B). It is noteworthy the
high degree of stereoselectivity observed for 6ad (14:1, Z:E),
which can be rationalized based on the preferential formation
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Scheme 3. Synthesis of Cyclopropyl-I(III) Compound 23

Marie Skłodowska-Curie Individual Fellowships (794815) (to
L.J.), as well as AEI for a FPI predoctoral fellowship (BES2017-080163) (to P.S.).

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(1) Hartwig, J. F. Organotransition Metal Chemistry From Bonding to
Catalysis; University Science Books, 2010.
(2) (a) Fischer, E. O.; Kreis, G.; Kreiter, C. G.; Müller, J.; Huttner,
G.; Lorenz, H. trans-Halogeno[alkyl(aryl)carbyne]tetracarbonyl
Complexes of Chromium, Molybdenum, and Tungsten -A New
Class of Compounds Having a Transition Metal-Carbon Triple Bond.
Angew. Chem., Int. Ed. Engl. 1973, 12, 564−565. (b) Guggenberger, L.
J.; Schrock, R. R. Tantalum carbyne complex. J. Am. Chem. Soc. 1975,
97, 2935−2935.
(3) Fürstner, A. Alkyne Metathesis on the Rise. Angew. Chem., Int.
Ed. 2013, 52, 2794−2819.
(4) Engel, P. F.; Pfeffer, M. Carbon-Carbon and CarbonHeteroatom Coupling Reactions of Metallacarbynes. Chem. Rev.
1995, 95, 2281−2309.
(5) Wang, Z.; Herraiz, A. G.; del Hoyo, A. M.; Suero, M. G.
Generating Carbyne Equivalents with Photoredox Catalysis. Nature
2018, 554, 86−91.
(6) For a review in photoredox catalysis, see: Shaw, M. H.; Twilton,
J.; MacMillan, D. W. C. Photoredox Catalysis in Organic Chemistry. J.
Org. Chem. 2016, 81, 6898−6926.
(7) (a) Minh, T. D.; Gunning, H. E.; Strausz, O. P. Formation and
Reaction of Monovalent Carbon Intermediates. I. Photolysis of
Diethyl Mercuribisdiazoacetate. J. Am. Chem. Soc. 1967, 89, 6785−
6787. (b) Strausz, O. P.; Thap, D. M.; Font, J. Formation and
Reactions of Monovalent Carbon Intermediates. II. Further Studies
on the Decomposition of Diethyl Mercurybisdiazoacetate. J. Am.
Chem. Soc. 1968, 90, 1930−1931. (c) Strausz, O. P.; Kennepohl, G. J.
A.; Garneau, F. X.; Minh, T. D.; Kim, B.; Valenty, S.; Skell, P. S.
Formation and Reactions of Monovalent Carbon Intermediates. III.
Reaction of Carbethoxymethyne with Olefins. J. Am. Chem. Soc. 1974,
96, 5723−5732. (d) Patrick, T. B.; Kovitch, G. H. Photolysis of
Diethyl Mercurybisdiazoacetate and Ethyl Diazoacetate in Chloroalkanes. J. Org. Chem. 1975, 40, 1527−1528. (e) Patrick, T. B.; Wu,
T. T. Photodecomposition of Diethyl Mercurybis(Diazoacetate) in
Several Heterocyclic Systems. J. Org. Chem. 1978, 43, 1506−1509.
(f) Bino, A. Formation of a Carbon-Carbon Triple Bond by Coupling
Reactions In Aqueous Solution. Science 2005, 308, 234−235.
(g) Bejot, R.; He, A.; Falck, J. R.; Mioskowski, C. Chromium−
Carbyne Complexes: Intermediates for Organic Synthesis. Angew.
Chem., Int. Ed. 2007, 46, 1719−1722. (h) Bogoslavsky, B.; Levy, O.;
Kotlyar, A.; Salem, M.; Gelman, F.; Bino, A. Do Carbyne Radicals
Really Exist in Aqueous Solution? Angew. Chem., Int. Ed. 2012, 51,
90−94. (i) Levy, O.; Bino, A. Metal Ions Do Not Play a Direct Role in
the Formation of Carbon-Carbon Triple Bonds during Reduction of
Trihaloalkyls by CrII or VII. Chem. - Eur. J. 2012, 18, 15944−15947.
(j) Zeng, T.; Wang, H.; Lu, Y.; Xie, Y.; Wang, H.; Schaefer, H. F.;
Ananth, N.; Hoffmann, R. Tuning Spin-States of Carbynes and
Silylynes: A Long Jump with One Leg. J. Am. Chem. Soc. 2014, 136,
13388−13398.
(8) (a) Weiss, R.; Seubert, J.; Hampel, F. α-Aryliodonio Diazo
Compounds: SN Reactions at the α-C Atom as a Novel Reaction Type
for Diazo Compounds. Angew. Chem., Int. Ed. Engl. 1994, 33, 1952−
1953. (b) Schnaars, C.; Hennum, M.; Bonge-Hansen, T. Nucleophilic
Halogenations of Diazo Compounds, a Complementary Principle for
the Synthesis of Halodiazo Compounds: Experimental and Theoretical Studies. J. Org. Chem. 2013, 78, 7488−7497. (c) Taylor, M. T.;
Nelson, J. E.; Suero, M. G.; Gaunt, M. J. A Protein Functionalization
Platform Based on Selective Reactions at Methionine Residues.
Nature 2018, 562, 563−568. For reviews in hypervalent iodine
chemistry, see: (d) Zhdankin, V. V.; Stang, P. J. Chemistry of
Polyvalent Iodine. Chem. Rev. 2008, 108, 5299−5358. (e) Li, Y.; Hari,
D. P.; Vita, M. V.; Waser, J. Cyclic Hypervalent Iodine Reagents for

simple nucleophiles into valuable allylic building blocks. The
value of the constructive scission of C(sp2)C(sp2) bonds in
alkenes for the synthesis of more substituted ones is
remarkable and is well exempliﬁed with the synthesis of allcarbon tetrasubstituted alkenes from readily available starting
materials. The isolation of a cyclopropyl-I(III) compound,
which opens following the Woodward−Hoﬀmann−DePuy
rules, clearly proves the involvement of these species as
intermediates in the reaction. We anticipate that the insertion
of a monovalent carbon unit in C(sp2)−C(sp2) bonds
underscores an opportunity as a tool in skeletal editing that
will be relevant to reach previously unattainable chemical space
in drug discovery.24

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ASSOCIATED CONTENT

S
* Supporting Information

The Supporting Information is available free of charge on the
ACS Publications website at DOI: 10.1021/jacs.9b08632.
X-ray crystallographic data for 6n (CIF)
X-ray crystallographic data for 6g (CIF)
X-ray crystallographic data for 23 (CIF)
Experimental procedures and spectral data (PDF)

■

REFERENCES

AUTHOR INFORMATION

Corresponding Author

*mgsuero@iciq.es
ORCID

Zhaofeng Wang: 0000-0002-0547-8172
Liyin Jiang: 0000-0002-6150-1787
Pau Sarró: 0000-0002-0957-2481
Marcos G. Suero: 0000-0001-9796-7768
Author Contributions
‡

These authors contributed equally to this work.

Notes

The authors declare no competing ﬁnancial interest.

■

ACKNOWLEDGMENTS
The ICIQ Starting Career Programme, Agencia Estatal de
Investigación (AEI) of the Ministerio de Ciencia, Innovación y
Universidades (CTQ2016-75311-P, FEDER-EU), the CELLEX Foundation through the CELLEX-ICIQ high-throughput
experimentation platform and the CERCA Programme
(Generalitat de Catalunya) are gratefully acknowledged for
ﬁnancial support. We thank the European Union for a Marie
Curie-COFUND postdoctoral fellowship (to Z.W.) and for a
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Atom-Transfer Reactions: Beyond Trifluoromethylation. Angew.
Chem., Int. Ed. 2016, 55, 4436−4454.
(9) (a) Doyle, M. P.; Forbes, D. C. Recent Advances in Asymmetric
Catalytic Metal Carbene Transformations. Chem. Rev. 1998, 98, 911−
936. (b) Davies, H. M. L.; Beckwith, R. E. J. Catalytic Enantioselective
C-H Activation by Means of Metal-Carbenoid-Induced C-H
Insertion. Chem. Rev. 2003, 103, 2861−2904.
(10) Okuyama, T.; Takino, T.; Sueda, T.; Ochiai, M. Solvolysis of
Cyclohexenyliodonium Salt, a New Precursor for the Vinyl Cation:
Remarkable Nucleofugality of the Phenyliodonio Group and Evidence
for Internal Return from an Intimate Ion−Molecule Pair. J. Am. Chem.
Soc. 1995, 117, 3360−3367.
(11) Vougioukalakis, G. C.; Grubbs, R. H. Ruthenium-Based
Heterocyclic Carbene-Coordinated Olefin Metathesis Catalysts.
Chem. Rev. 2010, 110, 1746−1787.
(12) Ludwig, J. R.; Zimmerman, P. M.; Gianino, J. B.; Schindler, C.
S. Iron(III)-catalysed Carbonyl−olefin Metathesis. Nature 2016, 533
(7603), 374−379.
(13) Jiménez-Núñez, E. S.; Echavarren, A. M. Gold-Catalyzed
Cycloisomerizations of Enynes: A Mechanistic Perspective. Chem.
Rev. 2008, 108, 3326−3350.
(14) For recent selected examples, see: (a) Xia, Y.; Lu, G.; Liu, P.;
Dong, G. Catalytic Activation of Carbon-Carbon Bonds in Cyclopentanones. Nature 2016, 539 (7630), 546−550. (b) Roque, J. B.;
Kuroda, Y.; Gö ttemann, L. T.; Sarpong, R. Deconstructive
Fluorination of Cyclic Amines by Carbon-Carbon Cleavage. Science
2018, 361, 171−174. (c) Xu, Y.; Qi, X.; Zheng, P.; Berti, C. C.; Liu,
P.; Dong, G. Deacylative Transformations of Ketones via Aromatization-promoted C−C Bond Activation. Nature 2019, 567, 373−378.
(d) Smaligo, A. J.; Swain, M.; Quintana, J. C.; Tan, M. F.; Kim, D. A.;
Kwon, O. Hydrodealkenylative C(Sp3)−C(Sp2) Bond Fragmentation.
Science 2019, 364, 681−685. For a review: (e) Souillart, L.; Cramer,
N. Catalytic C-C Bond Activations via Oxidative Addition to
Transition Metals. Chem. Rev. 2015, 115, 9410−9464.
(15) (a) Trost, B. M.; Crawley, M. L. Asymmetric Transition-MetalCatalyzed Allylic Alkylations:Applications in Total Synthesis. Chem.
Rev. 2003, 103, 2921−2944. (b) López, F.; Minnaard, A. J.; Feringa,
B. L. Catalytic Enantioselective Conjugate Addition and Allylic
Alkylation Reactions Using Grignard Reagents. Chem. Rev. 2008, 108,
2824−2852. (c) Cheng, Q.; Tu, H.-F.; Zheng, C.; Qu, J.-P.;
Helmchen, G.; You, S.-L. Iridium-Catalyzed Asymmetric Allylic
Substitution Reactions. Chem. Rev. 2019, 119, 1855−1969.
(16) Newton, C. G.; Wang, S.-G.; Oliveira, C. C.; Cramer, N.
Catalytic Enantioselective Transformations Involving C−H Bond
Cleavage by Transition-Metal Complexes. Chem. Rev. 2017, 117,
8908−8976.
(17) (a) von R. Schleyer, P.; Van Dine, G. W.; Schöllkopf, U.; Paust,
J. Steric and Electrocyclic Control of Cyclopropyl Tosylate Solvolysis
Rates. J. Am. Chem. Soc. 1966, 88, 2868−2869. (b) Baird, M. S.;
Lindsay, D. G.; Reese, C. B. Thermal Rearrangement of
Halogenocarbene Adducts of Cyclic Olefins. J. Chem. Soc. C 1969,
8, 1173−1178. (c) Fedoryński, M. Syntheses of Gem-Dihalocyclopropanes and Their Use in Organic Synthesis. Chem. Rev. 2003, 103,
1099−1132.
(18) (a) Woodward, R. B.; Hoffmann, R. Stereochemistry of
Electrocyclic Reactions. J. Am. Chem. Soc. 1965, 87, 395−397.
(b) DePuy, C. H. The Chemistry of Cyclopropanols. Acc. Chem. Res.
1968, 1, 33−41. (c) Nieto Faza, O.; Silva López, C.; Á lvarez, R.; De
Lera, Á . R. Solvolytic Ring-Opening Reactions of Cyclopropyl
Bromides. An Assessment of the Woodward-Hoffmann-DePuy Rule.
J. Org. Chem. 2004, 69, 9002−9010.
(19) Espino, C. G.; Fiori, K. W.; Kim, M.; Du Bois, J. Expanding the
Scope of C-H Amination through Catalyst Design. J. Am. Chem. Soc.
2004, 126, 15378−15379.
(20) At present, the exact mechanisms by which Rh-carbynoid 3
evolves, instead of cyclopropanation, is not fully understood. The
dimerization by coupling with 2e or C−H insertion with CH2Cl2, are
a priori the potential undesired pathways; however, we did not ﬁnd
reaction products that support such evolutions.

(21) See Supporting Information for further optimization.
(22) Flynn, A. B.; Ogilvie, W. W. Stereocontrolled Synthesis of
Tetrasubstituted Olefins. Chem. Rev. 2007, 107, 4698−4745.
(23) (a) Dence, J. B.; Roberts, J. D. Efforts Toward the Synthesis of
Aliphatic Iodonium Salts. J. Org. Chem. 1968, 33, 1251−1253.
(b) Olah, G. A.; De Member, J. R. Friedel-Crafts chemistry. IV.
Dialkylhalonium ions and their possible role in Friedel-Crafts
reactions. J. Am. Chem. Soc. 1969, 91, 2113−2115. (c) Morris, D.
G.; Shepherd, A. G. 4-Tricyclyliodonium Bis(m-Chlorobenzoate): A
Stable Aliphatic Trivalent Iodine Diester. J. Chem. Soc., Chem.
Commun. 1981, 24, 1250−1251. (d) Zhdankin, V. V.; Tykwinski, R.;
Caple, R.; Berglund, B.; Koz’min, A. S.; Zefirov, N. S. Reaction of
PhIO·HBF4/silyl Enol Ether Adduct with Olefins as General
Approach to Carboncarbon Bond Formation in AdE Reactions
Using Hypervalent Iodine Reagents. Tetrahedron Lett. 1988, 29,
3703−3704. For recent reviewshighlighting the prevalence of alkylI(III) as reactive intermediates, see: (e) Flores, A.; Cots, E.; Bergès, J.;
Muñ iz, K. Enantioselective Iodine(I/III) Catalysis in Organic
Synthesis. Adv. Synth. Catal. 2019, 361, 2−25. (f) Muñiz, K.;
Bosnidou, A. E. Alkyliodines in High Oxidation State: Enhanced
Synthetic Possibilities and Accelerated Catalyst Turn-Over. Chem. Eur. J. 2019, DOI: 10.1002/chem.201902687.
(24) Campos, K. R.; Coleman, P. J.; Alvarez, J. C.; Dreher, S. D.;
Garbaccio, R. M.; Terrett, N. K.; Tillyer, R. D.; Truppo, M. D.;
Parmee, E. R. The Importance of Synthetic Chemistry in the
Pharmaceutical Industry. Science 2019, 363, No. eaat0805.

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DOI: 10.1021/jacs.9b08632
J. Am. Chem. Soc. 2019, 141, 15509−15514