Allylboronates from vinyl triflates and α-chloroboronates by reductive nickel catalysis

Article abstract of DOI:10.1021/acs.orglett.0c01683

Allylboronates are unique building blocks widely used in organic synthesis, but the construction of cyclic allylboranates remains a challenging subject. We demonstrate here a mild and efficient access to this type of compound through the cross-electrophile coupling of vinyl triflates and α-chloroboronates. The reaction proceeded with a good substrate scope and good functional group compatibility. The ready availability of vinyl triflates from ketones, as well as the rich chemistry of allylboranates, makes our method suitable for the divergent modification of biologically active compounds. Preliminary mechanistic studies revealed that α-chloroboronates were activated via a radical process.

Full text of DOI:10.1021/acs.orglett.0c01683

pubs.acs.org/OrgLett
Letter
Allylboronates from Vinyl Triflates and α‑Chloroboronates by
Reductive Nickel Catalysis
Jin-Bao Qiao, Zhen-Zhen Zhao, Ya-Qian Zhang, Kai Yin, Zhi-Xiong Tian, and Xing-Zhong Shu*
Cite This: https://dx.doi.org/10.1021/acs.orglett.0c01683
Read Online
sı
*
Metrics & More
Article Recommendations
Supporting Information
ACCESS
ABSTRACT: Allylboronates are unique building blocks widely
used in organic synthesis, but the construction of cyclic
allylboranates remains a challenging subject. We demonstrate
here a mild and efficient access to this type of compound through
the cross-electrophile coupling of vinyl triflates and α-chlorobor-
onates. The reaction proceeded with a good substrate scope and
good functional group compatibility. The ready availability of vinyl
triflates from ketones, as well as the rich chemistry of allylboranates, makes our method suitable for the divergent modification of
biologically active compounds. Preliminary mechanistic studies revealed that α-chloroboronates were activated via a radical process.
One strategy that could be used to overcome this limitation
would be the reaction of well-defined vinyl species with α-
haloboronates (Scheme 1).10 In this context, the nucleophilic
substitution reactions using vinyl metallic species (e.g., vinyl−
M, M = Li, Mg, Al, Cu) represent the current state-of-the-art
(Scheme 1a). However, partially because of the difficulty in
accessing cyclic vinyl metals, these reactions have rarely been
investigated for the synthesis of cyclic allylboronates. The use
of vinyl electrophiles instead of vinyl metals is advantageous in
availability, and it would provide access to a complementary
scope of synthetically useful products. However, to our
knowledge, there has been no report on the reaction between
vinyl electrophiles and α-haloboronates.
The cross-electrophile coupling has recently emerged as a
powerful tool for forging C−C bonds between electrophiles.11
Among the various coupling partners, the amphoteric reagents
such as α-haloboronates and α-halosilanes are particularly
attractive.12 These reagents possess nucleophilic and electro-
philic sites, thus offering a versatile platform for chemoselective
transformations. Recent elegant work by the Martin group has
demonstrated the possibility of chemoselective arylation and
alkylation of α-haloboronates with aryl bromides and alkenes,
respectively.12b However, the cross-electrophile vinylation
reaction is still unknown. As part of our ongoing interest in
reductive vinylation reactions,13 here we demonstrate a cross-
electrophile coupling of vinyl triflates14 with α-haloboronates
(Scheme 1b). This method provides a mild and efficient
llylboronates are essential building blocks frequently used
Ain the synthesis of natural compounds and pharmaceut-
icals.1 They have widely served as coupling partners in the
Suzuki−Miyaura reaction for the precise installation of an allyl
group.2 They are also used as nucleophiles for additions to
aldehydes and imines to afford homoallylic alcohols and
amines.1 Therefore, the synthesis of allylboronates has received
considerable attention over the past years.3 Approaches to
these compounds typically include,4 but are not limited to, (1)
the boration reactions of allylic substrates such as allyl
nucleophiles,5 electrophiles (e.g., halides, acetates, alcohols),6
and C−H bonds,7 (2) the hydroboration or diboration
reactions of 1,3-dienes,8 and (3) the hydroboration reactions
of allenes.9 Despite these promising advances, these processes
are generally effective for the synthesis of acyclic allylboro-
nates. To date, a method for the construction of cyclic
allylboronates, with the structure shown in Scheme 1b, remains
to be developed.
Scheme 1. Synthesis of Allylboronates from α-
Haloboronates
Received: May 18, 2020
https://dx.doi.org/10.1021/acs.orglett.0c01683
© XXXX American Chemical Society
Org. Lett. XXXX, XXX, XXX−XXX
A

Organic Letters
pubs.acs.org/OrgLett
Letter
a
approach to cyclic allylboronates that can be otherwise difficult
to access. It thus serves as a good complementary to the
existing methodologies for the construction of allylboronates.
We began our investigations by studying the reaction of α-
chloroboronate 1a with vinyl triflate 2a (Table 1). After
Table 2. Substrate Scope of Vinyl Triflates
a
Table 1. Optimization of Reaction Conditions
entry
change of conditions
3a (%)
b
1
2
3
4
5
6
7
8
none
NiCl2
NiI2
Ni(dme)Cl2
Ni(diglyme)Br2
L1 instead of bpy
L2 instead of bpy
L3 instead of bpy
L4 instead of bpy
no NaBr
r.t. instead of −15 °C
Zn instead of Mn
no Ni or Mn
86 (84)
80
82
74
77
61
4
71
35
78
61
22
0
9
10
11
12
13
a
1a (0.18 mmol) and 2a (0.1 mmol) were used. The yields were
b
determined by GC using dodecane as an internal standard. 1a (0.36
mmol) and 2a (0.2 mmol) were used. Isolated yield.
a
screening a range of reaction conditions (see Tables S1−S7),
we found that the combination of NiBr2 (10 mol %), bpy (22
mol %), NaBr (1.0 equiv), and Mn (3.0 equiv) in DMF at −15
°C gave the best result, affording 3a in 84% isolated yield
(entry 1). Compatible results were obtained when NiCl2 or
NiI2 was used, whereas the reactions with Ni(dme)Cl2 or
Ni(glyme)Br2 gave decreased yields (entries 2−5). The
inferior results were obtained when other nitrogen ligands
were used (entries 6−9). The presence of NaBr has a positive
effect on the yield, in which the formation of a vinyl dimer
byproduct was partly inhibited (entry 10). It is possible that
the in situ halide exchange of NaBr with α-chloroboronate
generates α-bromoboronate, which is more reactive and may
couple to vinyl triflate more efficiently. The reaction at room
temperature afforded a significant amount of vinyl dimer,
leading to a decreased yield (entry 11). The reaction with Zn
as a reductant was highly ineffective (entry 12). In the absence
of a nickel catalyst or reductant, no desired product was
observed (entry 13).
With the optimized reaction conditions in hand, we studied
the reaction with respect to the scope of vinyl triflates (Table
2). The cyclic vinyl triflates, ranging from five- to eight-
membered rings, coupled to 1a efficiently to afford the desired
products in moderate to good yields (3a−d). Whereas the 2-
substituted vinyl triflate resulted in a low yield of product 3e,
substitution at the 3- and 4-position was tolerated (3f−k). The
moderate yields of coupling products were obtained when
indenyl triflate (3l) and 3,4-dihydronaphthalenyl triflate (3m)
were used. Nonaromatic heterocycles are essential structural
1a (0.36 mmol) and vinyl triflates (0.2 mmol) were used. Isolated
b
yields. NMR yield was used because of the difficulty in purification
with the dechloro byproduct of α-chloroboronates. 4,7-Diphenyl-
1,10-phenanthroline was used instead of 2,2′-bipyridine. Phenyl
triflate (0.2 mmol) was used.
c
d
motifs found in various pharmaceuticals.15 Our method
provides an efficient approach to produce heterocyclic
allylboronates, including those bearing 3,6-dihydro-2H-thio-
pyran (3n) and 3-piperideine (3o) heterocycles. Reactions
with acyclic vinyl substrates were less effective under the
standard conditions. By changing the ligand to 4,7-diphenyl-
1,10-phenanthroline, the reactions with 1a afforded the desired
products in moderate yields (3p, 3q). Only a trace of product
was observed when all-substituted acyclic vinyl triflate was
used (3r). The use of phenyl triflate afforded the desired
product in 13% yield (3s). The abundance of ketones in nature
prompted us to investigate the potential of our method for the
functionalization of biologically active molecules. Testoster-
one- and estrone-derived vinyl triflates coupled to 1a
efficiently, and allylboronate 3t and 3u were produced in
moderate to good yield.
The substrate scope of α-chloroboronates is shown in Table
3. α-Chloroboronates with different chain lengths of the alkyl
group were tolerated (3v, 3w, 3x). The reactions with sterically
hindered substrates were less effective (3y, 3z). The presence
of an aryl group, bearing either electron-rich or electron-poor
substituents, at the alkyl chain was tolerated (3aa−ad). The
reaction has shown good functional group compatibility. α-
B
https://dx.doi.org/10.1021/acs.orglett.0c01683
Org. Lett. XXXX, XXX, XXX−XXX

Organic Letters
pubs.acs.org/OrgLett
Letter
a
Table 3. Substrate Scope of α-Chloroboronates
Scheme 3. Mechanistic Studies
a
2o (0.20 mmol) and α-chloroboronates (0.36 mmol) were used.
(2a)).16 (2) Under the standard conditions, the reaction of
alkene substrate 1q with 2a afforded the cyclized product 11 in
14% yield (Scheme 3 (2b)). (3) The reaction of racemic 1a
afforded allylboronate 12 in 22% ee when chiral ligand L* was
used (Scheme 3 (3)). These results are consistent with a
pathway in which a radical process might be involved in the
activation of α-chloroboronates.
Although the detailed mechanism for this reaction requires
further investigation, on the basis of the above results and on
reports presented by other investigators,17 we tentatively
proposed a catalytic cycle, as shown in Scheme 4. The
b
Isolated yields. Reactions for 36 h.
Chloroboronates with functionalities, such as alkene (3ae),
nitrile (3af), alkyl chloride (3ag), ether (3ah), and silyl ether
(3ai), could be selectively vinylated to afford the products in
moderate to good yields.
The modification of biologically active compounds repre-
sents a promising approach to alter their pharmacological
profiles. Our method offers the opportunity for the divergent
modification of these compounds. For example, estrone-
derived vinyl triflates could be functionalized with 1b on the
gram scale to afford allylboronate 3aj (Scheme 2). Because of
Scheme 4. Proposed Mechanism
Scheme 2. Synthetic Application
the rich chemistry of allylboronate, compound 3aj could
undergo divergent transformation to provide the hydration
product 4, the vinylation product 5, and the addition product
6.
In the presence of 1,1-diphenylethylene, the reaction of 1a
with 2a afforded 3a in 80% yield, along with 13% of alkene
trapping product 7 (Scheme 3 (1)). This result suggests that
α-chloroboronates might be activated via a radical mechanism.
To confirm this hypothesis, several control experiments were
performed. (1) The reaction of cyclopropyl substrate 1p with
2a exclusively produced the ring-opening product (Scheme 3
oxidative addition of vinyl triflate to Ni(0) would afford vinyl−
Ni(II) (A), which may trap an alkyl radical to afford complex
C.17a The reductive elimination of compound C would give the
desired product 3 and generate Ni(I). Alkyl radical B might be
generated via the single-electron reaction of α-chloroboronates
1 with Ni(I).17c
In summary, we have demonstrated the cross-electrophile
coupling of vinyl triflates with α-chloroboronates. This
C
https://dx.doi.org/10.1021/acs.orglett.0c01683
Org. Lett. XXXX, XXX, XXX−XXX

Organic Letters
pubs.acs.org/OrgLett
Letter
́
Compounds; Wiley: Hoboken, NJ, 2012. (d) Yus, M.; Gonzalez-
reaction offers a mild and efficient approach for the synthesis
of cyclic allylboronates, which are difficult to access otherwise.
The synthetic utility of this method was demonstrated by its
application to the divergent modification of biologically active
molecules. Preliminary mechanistic experiments revealed that a
radical process was involved in the activation of α-
chloroboronates. Further studies on the reductive vinylation
reactions are ongoing in our laboratories.
́
Gomez, J. C.; Foubelo, F. Diastereoselective Allylation of Carbonyl
Compounds and Imines: Application to the Synthesis of Natural
Products. Chem. Rev. 2013, 113, 5595.
(2) Selected references: (a) Sebelius, S.; Olsson, V. J.; Wallner, O.
A.; Szabo, K. J. Palladium-Catalyzed Coupling of Allylboronic Acids
with Iodobenzenes. Selective Formation of the Branched Allylic
Product in the Absence of Directing Groups. J. Am. Chem. Soc. 2006,
128, 8150. (b) Glasspoole, B. W.; Ghozati, K.; Moir, J. W.; Crudden,
C. M. Suzuki-Miyaura cross-couplings of secondary allylic boronic
esters. Chem. Commun. 2012, 48, 1230. (c) Yang, Y.; Buchwald, S. L.
Ligand-Controlled Palladium-Catalyzed Regiodivergent Suzuki-
Miyaura Cross-Coupling of Allylboronates and Aryl Halides. J. Am.
Chem. Soc. 2013, 135, 10642.
(3) An elegant review: Diner, C.; Szabo, K. J. Recent Advances in the
Preparation and Application of Allylboron Species in Organic
Synthesis. J. Am. Chem. Soc. 2017, 139, 2.
(4) For other represented approaches, see: (a) Yamamoto, Y.;
Takahashi, M.; Miyaura, N. Synthesis of Pinacol Allylic Boronic Esters
via Olefin Cross-Metathesis between Pinacol Allylboronate and
Terminal or Internal Alkenes. Synlett 2002, 1, 128. (b) Althaus, M.;
ASSOCIATED CONTENT
* Supporting Information
■
sı
The Supporting Information is available free of charge at
https://pubs.acs.org/doi/10.1021/acs.orglett.0c01683.
Detailed optimization of reaction conditions, part of the
mechanistic studies, detailed experimental procedures,
1
characterization data, and copies of H and 13C NMR
spectra for new compounds (PDF)
́
AUTHOR INFORMATION
Corresponding Author
Mahmood, A.; Suarez, J. R.; Thomas, S. P.; Aggarwal, V. K.
■
Application of the Lithiation-Borylation Reaction to the Preparation
of Enantioenriched Allylic Boron Reagents and Subsequent In Situ
Conversion into 1,2,4-Trisubstituted Homoallylic Alcohols with
Complete Control over All Elements of Stereochemistry. J. Am.
Chem. Soc. 2010, 132, 4025. (c) Potter, B.; Edelstein, E. K.; Morken, J.
P. Modular, Catalytic Enantioselective Construction of Quaternary
Carbon Stereocenters by Sequential Cross-Coupling Reactions. Org.
Lett. 2016, 18, 3286. (d) Edelstein, E. K.; Namirembe, S.; Morken, J.
P. Enantioselective Conjunctive Cross-Coupling of Bis(alkenyl)
Borates: A General Synthesis of Chiral Allylboron Reagents. J. Am.
Chem. Soc. 2017, 139, 5027.
Xing-Zhong Shu − State Key Laboratory of Applied Organic
Chemistry (SKLAOC), College of Chemistry and Chemical
Engineering, Lanzhou University, Lanzhou 730000, China;
orcid.org/0000-0002-0961-1508; Email: shuxingzh@
lzu.edu.cn
Authors
Jin-Bao Qiao − State Key Laboratory of Applied Organic
Chemistry (SKLAOC), College of Chemistry and Chemical
Engineering, Lanzhou University, Lanzhou 730000, China
Zhen-Zhen Zhao − State Key Laboratory of Applied Organic
Chemistry (SKLAOC), College of Chemistry and Chemical
Engineering, Lanzhou University, Lanzhou 730000, China
Ya-Qian Zhang − State Key Laboratory of Applied Organic
Chemistry (SKLAOC), College of Chemistry and Chemical
Engineering, Lanzhou University, Lanzhou 730000, China
Kai Yin − Shangyu Economic and Technological Development
Zone, Zhejiang Nanjiao Chemistry Co., Ltd., Shangyu 312369,
China
(5) (a) Roush, W. R.; Ando, K.; Powers, D. B.; Palkowitz, A. D.;
Halterman, R. L. Asymmetric Synthesis Using Diisopropyl Tartrate
Modified (E)- and (Z)-Crotylboronates: Preparation of the Chiral
Crotylboronates and Reactions with Achiral Aldehydes. J. Am. Chem.
Soc. 1990, 112, 6339. (b) Beckmann, E.; Hoppe, D. Synthesis of an
Enantioenriched a-Carbamoyloxy-crotylboronate and Its Homoaldol
Reaction with Aldehydes. Synthesis 2005, 217.
(6) Selected recent references, see: (a) Guzman-Martinez, A.;
Hoveyda, A. H. Enantioselective Synthesis of Allylboronates Bearing a
Tertiary or Quaternary B-Substituted Stereogenic Carbon by NHC-
Cu-Catalyzed Substitution Reactions. J. Am. Chem. Soc. 2010, 132,
10634. (b) Park, J. K.; Lackey, H. H.; Ondrusek, B. A.; McQuade, D.
T. Stereoconvergent Synthesis of Chiral Allylboronates from an E/Z
Mixture of Allylic Aryl Ethers Using a 6-NHC-Cu(I) Catalyst. J. Am.
Chem. Soc. 2011, 133, 2410. (c) Zhou, Q.; Srinivas, H. D.; Zhang, S.;
Watson, M. P. Accessing Both Retention and Inversion Pathways in
Stereospecific, Nickel-Catalyzed Miyaura Borylations of Allylic
Pivalates. J. Am. Chem. Soc. 2016, 138, 11989. (d) Miralles, N.;
Zhi-Xiong Tian − State Key Laboratory of Applied Organic
Chemistry (SKLAOC), College of Chemistry and Chemical
Engineering, Lanzhou University, Lanzhou 730000, China
Complete contact information is available at:
https://pubs.acs.org/10.1021/acs.orglett.0c01683
́
́
Gomez, J. E.; Kleij, A. W.; Fernandez, E. Copper-Mediated SN2’Allyl-
Alkyl and Allyl-Boryl Couplings of Vinyl Cyclic Carbonates. Org. Lett.
2017, 19, 6096. (e) Zhou, Y.; Wang, H.; Liu, Y.; Zhao, Y.; Zhang, C.;
Qu, J. Iron-catalyzed boration of allylic esters: an efficient approach to
allylic boronates. Org. Chem. Front. 2017, 4, 1580. (f) Chen, P.-P.;
Zhang, H.; Cheng, B.; Chen, X.; Cheng, F.; Zhang, S.-Q.; Lu, Z.;
Meng, F.; Hong, X. How Solvents Control the Stereospecificity of Ni-
Catalyzed Miyaura Borylation of Allylic Pivalates. ACS Catal. 2019, 9,
9589. (g) Ge, Y.; Cui, X.-Y.; Tan, S. M.; Jiang, H.; Ren, J.; Lee, N.;
Lee, R.; Tan, C.-H. Guanidine-Copper Complex Catalyzed Allylic
Borylation for the Enantioconvergent Synthesis of Tertiary Cyclic
Allylboronates. Angew. Chem., Int. Ed. 2019, 58, 2382.
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
We thank the National Natural Science Foundation of China
for its financial support (21772072). We acknowledge the
NMR facility at SKLAOC and Mr. Fengming Qi and Mr.
Songqing Liu for their expert assistance.
REFERENCES
■
́
(7) (a) Deng, H.-P.; Eriksson, L.; Szabo, K. J. Allylic sp3 C-H
(1) For selected reviews, see: (a) Denmark, S. E.; Fu, J. Catalytic
Enantioselective Addition of Allylic Organometallic Reagents to
Aldehydes and Ketones. Chem. Rev. 2003, 103, 2763. (b) Ramachan-
dran, P. V.; Burghardt, T. E. Recent developments in the chiral
synthesis of homoallylic amines via organoboranes. Pure Appl. Chem.
2006, 78, 1397. (c) Hall, D. G.; Lachance, H. Allylboration of Carbonyl
borylation of alkenes via allyl-Pd intermediates: an efficient route to
allylboronates. Chem. Commun. 2014, 50, 9207. (b) Tao, Z.-L.; Li, X.-
H.; Han, Z.-Y.; Gong, L.-Z. Diastereoselective Carbonyl Allylation
with Simple Olefins Enabled by Palladium Complex-Catalyzed C-H
Oxidative Borylation. J. Am. Chem. Soc. 2015, 137, 4054. (c) Mao, L.;
D
https://dx.doi.org/10.1021/acs.orglett.0c01683
Org. Lett. XXXX, XXX, XXX−XXX

Organic Letters
pubs.acs.org/OrgLett
Letter
́
Bertermann, R.; Rachor, S. G.; Szabo, K. J.; Marder, T. B. Palladium-
Catalyzed Oxidative Borylation of Allylic C-H Bonds in Alkenes. Org.
Lett. 2017, 19 (24), 6590.
(14) (a) Busacca, C. A.; Eriksson, M. C.; Fiaschi, R. Cross Coupling
of Vinyl Triflates and Aikyl Grignard Reagents Catalyzed by
Nickel(0)-Complexes. Tetrahedron Lett. 1999, 40, 3101. (b) Cho,
E. J.; Buchwald, S. L. The Palladium-Catalyzed Trifluoromethylation
of Vinyl Sulfonates. Org. Lett. 2011, 13, 6552. (c) Liao, L.; Jana, R.;
Urkalan, K. B.; Sigman, M. S. A Palladium-Catalyzed Three-
Component Cross-Coupling of Conjugated Dienes or Terminal
Alkenes with Vinyl Triflates and Boronic Acids. J. Am. Chem. Soc.
2011, 133, 5784. (d) Chen, H.; Sun, S.; Liao, X. Nickel-Catalyzed
Decarboxylative Alkenylation of Anhydrides with Vinyl Triflates or
Halides. Org. Lett. 2019, 21, 3625.
(15) Ferles, M.; Pliml, J. Adv. Heterocycl. Chem. 1970, 12, 43−101.
(16) Stevenson, J. P.; Jackson, W. F.; Tanko, J. M. Cyclo-
propylcarbinyl-Type Ring Openings. Reconciling the Chemistry of
Neutral Radicals and Radical Anions. J. Am. Chem. Soc. 2002, 124,
4271.
(8) (a) Wu, J. Y.; Moreau, B.; Ritter, T. Iron-Catalyzed 1,4-
Hydroboration of 1,3-Dienes. J. Am. Chem. Soc. 2009, 131, 12915.
(b) Ely, R. J.; Morken, J. P. Regio- and Stereoselective Ni-Catalyzed
1,4-Hydroboration of 1,3-Dienes: Access to Stereodefined (Z)-
Allylboron Reagents and Derived Allylic Alcohols. J. Am. Chem. Soc.
2010, 132, 2534. (c) Peng, S.; Yang, J.; Liu, G.; Huang, Z. Ligand
controlled cobalt catalyzed regiodivergent 1,2-hydroboration of 1,3-
dienes. Sci. China: Chem. 2019, 62, 336. (d) Wang, M.; Gao, S.; Chen,
M. Stereoselective Syntheses of (E)-γ,δ-Bisboryl-Substituted syn-
Homoallylic Alcohols via Chemoselective Aldehyde Allylboration.
Org. Lett. 2019, 21, 2151.
(9) Yuan, W.; Song, L.; Ma, S. Copper-Catalyzed Borylcupration of
Allenylsilanes. Angew. Chem., Int. Ed. 2016, 55, 3140.
(17) (a) Biswas, S.; Weix, D. J. Mechanism and Selectivity in Nickel-
Catalyzed Cross-Electrophile Coupling of Aryl Halides with Alkyl
Halides. J. Am. Chem. Soc. 2013, 135, 16192. (b) Everson, D. A.;
Weix, D. J. Cross-Electrophile Coupling: Principles of Reactivity and
Selectivity. J. Org. Chem. 2014, 79, 4793. (c) Diccianni, J. B.; Diao, T.
Mechanisms of Nickel-Catalyzed Cross-Coupling Reactions. Trends in
Chemistry 2019, 1, 830.
(10) (a) Brown, H. C.; De Lue, N. R.; Yamamoto, Y.; Maruyama, K.;
Kasahara, T.; Murahashi, S.; Sonoda, A. Organoboranes. 23. Reaction
of Organolithium and Grignard Reagents with α-Bromoalkylboronate
Esters. A Convenient, Essentially Quantitative Procedure for the
Synthesis of Tertiary Alkyl-, Benzyl-, Propargyl-, and Stereospecific
Allylboranes. J. Org. Chem. 1977, 42, 4088. (b) Matteson, D. S.;
Majumdar, D. α-Chloro Boronic Esters from Homologation of
Boronic Esters. J. Am. Chem. Soc. 1980, 102, 7588. (c) Nyzam, V.;
́
Belaud, C.; Villieras, J. Preparation of (2-methoxycarbonyl)-
allylboronates from (ol-methoxycarbonyl)vinylalanate. Tetrahedron
Lett. 1993, 34, 6899. (d) Kennedy, J. W. J.; Hall, D. G. Novel
Isomerically Pure Tetrasubstituted Allylboronates: Stereocontrolled
Synthesis of r-Exomethylene γ-Lactones as Aldol-Like Adducts with a
Stereogenic Quaternary Carbon Center. J. Am. Chem. Soc. 2002, 124,
898.
(11) For recent reviews of the cross-electrophile reactions, see:
̈
(a) Knappke, C. E. I.; Grupe, S.; Gartner, D.; Corpet, M.; Gosmini,
C.; Jacobi von Wangelin, A. Reductive Cross-Coupling Reactions
between Two Electrophiles. Chem. - Eur. J. 2014, 20, 6828.
(b) Moragas, T.; Correa, A.; Martin, R. Metal-Catalyzed Reductive
Coupling Reactions of Organic Halides with Carbonyl Type
Compounds. Chem. - Eur. J. 2014, 20, 8242. (c) Weix, D. J. Methods
and Mechanisms for Cross-Electrophile Coupling of Csp2 Halides
with Alkyl Electrophiles. Acc. Chem. Res. 2015, 48, 1767. (d) Gu, J.;
Wang, X.; Xue, W.; Gong, H. Nickel-catalyzed Reductive Coupling of
Alkyl Halides with Other Electrophiles: Concept and Mechanistic
Considerations. Org. Chem. Front. 2015, 2, 1411. (e) Lucas, E. L.;
Jarvo, E. R. Stereospecific and Stereoconvergent Cross-couplings
between Alkyl Electrophiles. Nat. Rev. Chem. 2017, 1, 0065.
(f) Richmond, E.; Moran, J. Recent Advances in Nickel Catalysis
Enabled by Stoichiometric Metallic Reducing Agents. Synthesis 2018,
50, 499.
(12) (a) Hofstra, J. L.; Cherney, A. H.; Ordner, C. M.; Reisman, S.
E. Synthesis of Enantioenriched Allylic Silanes via Nickel-Catalyzed
Reductive Cross-Coupling. J. Am. Chem. Soc. 2018, 140, 139. (b) Sun,
S.-Z.; Martin, R. Nickel-Catalyzed Umpolung Arylation of Ambiphilic
α-Bromoalkyl Boronic Esters. Angew. Chem., Int. Ed. 2018, 57, 3622.
̈
(c) Sun, S.-Z.; Borjesson, M.; Martin-Montero, R. M.; Martin, R. Site-
Selective Ni-Catalyzed Reductive Coupling of α-Haloboraneswith
Unactivated Olefins. J. Am. Chem. Soc. 2018, 140, 12765.
(13) (a) Tian, Z.-X.; Qiao, J.-B.; Xu, G.-L.; Pang, X.; Qi, L.; Ma, W.-
Y.; Zhao, Z.-Z.; Duan, J.; Du, Y.-F.; Su, P.; Liu, X.-Y.; Shu, X.-Z.
Highly Enantioselective Cross-Electrophile Aryl-Alkenylation of
Unactivated Alkenes. J. Am. Chem. Soc. 2019, 141, 7637. (b) Pan,
F.-F.; Guo, P.; Li, C.-L.; Su, P.; Shu, X.-Z. Enones from Acid Fluorides
and Vinyl Triflates by Reductive Nickel Catalysis. Org. Lett. 2019, 21,
3701. (c) He, R.-D.; Li, C.-L.; Pan, Q.-Q.; Guo, P.; Liu, X.-Y.; Shu, X.-
Z. Reductive Coupling between C-N and C-OElectrophiles. J. Am.
Chem. Soc. 2019, 141, 12481. (d) Duan, J.; Du, Y.-F.; Pang, X.; Shu,
X.-Z. Ni-catalyzed cross-electrophile coupling betweenvinyl/aryl and
alkyl sulfonates: synthesis of cycloalkenes and modification of
peptides. Chem. Sci. 2019, 10, 8706.
E
https://dx.doi.org/10.1021/acs.orglett.0c01683
Org. Lett. XXXX, XXX, XXX−XXX