Dual Functionalization of α-Monoboryl Carbanions through Deoxygenative Enolization with Carboxylic Acids

Article abstract of DOI:10.1002/anie.201801679

A dual functionalization of 1,1-diborylalkanes through deoxygenative enolization with carboxylic acids was developed. 1,1-Diborylalkanes were activated by MeLi to generate α-monoboryl carbanions. In situ IR spectroscopy indicated an interaction between carboxylic acid and 1,1-diborylalkane before addition of the activation reagent. Release of the active α-monoboryl carbanion from the masked form was necessary for its reaction with carboxylate to afford enolate species. Electrophilic trapping of enolate species with various electrophiles achieved dual functionalization of 1,1-diborylalkanes to afford a variety of α-mono, di-, and tri-substituted ketones.

Full text of DOI:10.1002/anie.201801679

A Journal of the Gesellschaft Deutscher Chemiker
Angewandte
Chemie
International Edition
www.angewandte.org
Accepted Article
Title: Dual Functionalization of α-Monoboryl Carbanion via A
Deoxygenative Enolization with Carboxylic Acids
Authors: Wei Sun, Lu Wang, Chungu Xia, and Chao Liu
This manuscript has been accepted after peer review and appears as an
Accepted Article online prior to editing, proofing, and formal publication
of the final Version of Record (VoR). This work is currently citable by
using the Digital Object Identifier (DOI) given below. The VoR will be
published online in Early View as soon as possible and may be different
to this Accepted Article as a result of editing. Readers should obtain
the VoR from the journal website shown below when it is published
to ensure accuracy of information. The authors are responsible for the
content of this Accepted Article.
To be cited as: Angew. Chem. Int. Ed. 10.1002/anie.201801679
Angew. Chem. 10.1002/ange.201801679
Link to VoR: http://dx.doi.org/10.1002/anie.201801679
http://dx.doi.org/10.1002/ange.201801679

10.1002/anie.201801679
Angewandte Chemie International Edition
COMMUNICATION
Dual Functionalization of α-Monoboryl Carbanion via A
Deoxygenative Enolization with Carboxylic Acids
Wei Sun, Lu Wang, Chungu Xia,* and Chao Liu*
Dedicated to Professor Xiyan Lu on the occasion of his 90th birthday
Abstract: Dual functionalization of 1,1-diborylalkanes via
a
However, in most cases, selective mono-functionalizations were
achieved, due to that the resulting mono-boryl alkanes are
relatively inert coupling partners.
deoxygenative enolization with carboxylic acids strategy has been
developed for the first time. 1,1-Diborylalkanes were activated by
MeLi to generate -monoboryl carbanion. In-situ IR spectroscopy
exhibited the interaction between carboxylic acid and 1,1-
diborylalkane before adding activation reagent. The release of active
-monoboryl carbanion from its masked form was necessary for its
reaction with carboxylate to afford enolate species. Electrophilic
trapping of enolate species with various electrophiles achieved dual
functionalization of 1,1-diborylalkanes to afford a variety of -mono,
di- and tri-substituted ketones.
To achieve di-functionalization of both C-B bonds of 1,1-
diborylalkanes, we envisioned that firstly introducing an acyl
group to form an enolate boron species would facilitate the in-situ
activation of the second C-boryl group. A subsequent trapping
with a proper electrophile (E) would achieve the selective dual
functionalization of 1,1-diborylalkanes (Scheme 1). Esters and
acyl chorides have been used as the acyl synthons for the
enolization of both -diboryl and -monoboryl carbanion via
carbonyl addition processes.[2d, 4a, 6] Matteson has used proton as
the trapping electrophile,[2d, 4a] and very recently, Pattison used
NFSI, trichloroisocyanuric acid and MeI as the trapping
electrophiles in the enolization processes with -diboryl
carbanion.[7] Mukaiyama, Pelter used proton or aldehyde as the
Organoboron compounds are versatile building block in chemical
science. The readily transformable ability of C-B bonds makes
organoboron compounds indispensable in nowadays synthetic
chemistry.[1] Among various organoboron compounds, 1,1-
diborylalkanes have drawn increasing attention in recent years
due to its potential mono- or di-functionalizations to access value-
added chemicals. Moreover, many efforts on the synthesis of this
type of compounds make them readily accessible in nowadays.[2]
However, the selective di-functionalization of those two C-B
bonds of 1,1-diborylalkanes is still underdeveloped.[3]
Due to the empty p-orbital of boron, boryl group not only can
activate its gem-chemical bonds and stabilize its -carbanion, but
also can be activated by Lewis bases. Therefore, there are two
general modes for 1,1-diborylalkane activation. One is the direct
deprotonation of -CH with strong base such as LiTMP to
generate an -diboryl carbanion. However, this approach is
limited to terminal -CH containing 1,1-diborylalkanes and the
activating reagents are limited to strong amine-bases. These
limitations restricted the scope of 1,1-diborylalkanes in synthetic
applications.[2d, 4] The other mode is the coordination of Lewis
base to one boryl group of 1,1-diborylalkanes. In this case, -
monoboryl carbanion is usually presented as a reactive species.
Since the Lewis base can be variated from hydroxide, alkoxide to
alkylates, diverse transformations could be designed and
developed.[5] Therefore, more attention has been paid to this
activation mode for the transformation of 1,1-diborylalkanes.
trapping electrophiles in the enolization processes with -
6d]
monoboryl carbanion.[6c,
However, the direct utilization of
carboxylic acids as the acyl synthons for such enolization process
has not been disclosed to date. Carboxylic acids are widely
accesible yet they are relatively inert towards addition process
and the acidic proton may cause the carbanions quenching
problem. We reckoned that the potential coordination of
carboxylate to the boryl group may activate its carbonyl and thus
accomplishing the hypothesis. Herein, we demonstrated our
recent progress on the application of carboxylic acids as the acyl
synthons for the enolization of -monoboryl carbanion, followed
by electrophilic trapping with a variety of electrophiles. As a result,
a process of dual functionalization of 1,1-diborylalkanes was
established. Importantly, various -mono-, di- and tri-substituted
ketones can be selectively obtained by tuning R1, R2 and E groups
(Scheme 1). Moreover, the experimental manipulation is simple.
Directly mixing 1,1-diborylalkane and acid in toluene, adding
methyllithium (MeLi) under a low temperature, followed by heating
at 100 oC gave the desired enolate species. Further electrophilic
trapping generated ketones as the dual functionalization products.
[*]
W. Sun, Dr. L. Wang, Prof. Dr. C. Xia, Prof. Dr. C. Liu
State Key Laboratory for Oxo Synthesis and Selective Oxidation
Suzhou Research Institute of LICP, Lanzhou Institute of Chemical
Physics (LICP), Chinese Academy of Sciences
Lanzhou 730000, P. R. China
Scheme 1. Dual Functionalization of -Monoboryl Carbanion via
A
Deoxygenative Enolization with Carboxylic Acids.
Considering that acid may protonate the C-B bonds in 1,1-
diborylalkanes during the activation process, MeLi was applied as
the activating reagent. Consequently, the acidic proton will be
converted into methane which will not affect the following reaction
process. Meanwhile, MeLi has been demonstrated as a practical
reagent for 1,1-diborylalkane activation to generate -monoboryl
E-mail: cgxia@licp.cas.cn; chaoliu@licp.cas.cn
W. Sun
University of Chinese Academy of Sciences
Beijing, 100049 (China)
Supporting information for this article is given via a link at the end of
the document.
This article is protected by copyright. All rights reserved.

10.1002/anie.201801679
Angewandte Chemie International Edition
COMMUNICATION
8]
carbanion.[6d,
3-Phenyl-1,1-diborylpropane (1a) and benzoic
acid (2a) were used as the standard substrates. Theoretically,
MeLi was used to convert 2a to PhCOOLi and to activate 1a to
form an -monoboryl carbanion. Thus, 2.5 equivalents of MeLi
were added to the mixture of 1a (1.5 equiv) and 2a (1.0 equiv) in
o
toluene at -30 C. No coupling product was observed at room
temperature. Upon heating the mixture at 100 oC for 8 hours, the
desired -deuterated ketone 3aa-1 was isolated in 88% yield by
using D2O as the trapping electrophile (3aa-1; H2O gave 90%
yield of 3aa-2, Eq.1). Furthermore, 1H NMR spectrum of the
reaction between 1a and 2a without electrophilic quenching
showed an enolate -CH signal at 4.45 ppm. Its IR spectrum
clearly showed no carbonyl absorbance. However, after being
quenched by HCl, the 1689 cm-1 peak of 3aa-2 appeared
obviously (by comparison with its standard spectrum, See SI).
These results supported that boron enolate species was
generated in the reaction mixture.
Scheme 2. Investigation on trapping electrophiles. Reaction conditions: 1) 1
(0.375 mmol), 2 (0.25 mmol), MeLi (0.625 mmol), toluene or THF (2.0 mL), -30
oC, 5 min then 100 oC, 8 h; 2) E+ (0.50 mmol), 100 oC, 6 h; [a] E4 (1.2 equiv); [b]
E4, 24 h, r.t.; Yields based on isolated products.
Since boron enolate was successfully generated from 1,1-
diborylalkanes and carboxylic acids, it allows for further
electrophilic functionalization with various electrophiles to finally
result in versatile hetero di-functionalization of 1,1-diborylalkanes.
Then, 1a and 2a were majorly applied to test various electrophiles
(Scheme 2 and Scheme 3). Using 1-iodohexane (E1) as the
electrophile resulted in the alkylation product 3aa-3 in 58% yield.
When 4-methoxybenzoyl chloride (E2) was used, the
corresponding unsymmetrical di-acylation of 1a was achieved to
give 1,3-diketone 3aa-4. When methyl bromoacetate (E3) was
used, 1,4-dicarbonyl compound 3aa-5 was obtained in 52% yield.
Those dicarbonyl compounds 3aa-4 and 3aa-5 are appealing
precursors of heteroaromatic cycles. Using Eschenmoser’s salt
(E4) as the trapping electrophile accordingly provided the free
Mannich Base 3aa-6 in 84% yield when 1.2 equivalents of E4 was
used. Interestingly, 2.0 equivalents of E4 gave an ,-unsaturated
ketone 3aa-7 in 60% yield, indicating that 3aa-6 was further
alkylated by excess E4 and eliminated to give 3aa-7 under the
reaction condition.[5b] Further applications of allyl chloride (E5),
propynyl bromide (E6), iodoacetonitrile (E7), and benzylic halides
(E8, E9) afforded their corresponding electrophilic trapping
products 3aa-8, 3aa-9, 3aa-10, 3aa-11, and 3aa-12 in moderate
to excellent yields. Secondary benzylic bromide E10 also worked
well to afford 3aa-13 in 81% yield, while secondary cyclohexyl
bromide only produced trace amount of the desired coupling
product. In those cases, -mono- and di-substituted ketones were
obtained with 1a as the substrate. When non-terminal 1,1-
diborylalkanes were applied, -tri-substituted ketones 3aa-14 and
3aa-15 were obtained by using E9 as the trapping electrophile. It
was worthy of note that aryl bromides were also successfully
applied as the trapping electrophiles in the presence of palladium
catalyst (Scheme 3).[9] Phenyl bromides bearing p-OMe (E11), m-
OMe (E12) or p-NMe2 (E13) groups were well tolerated. Other
aromatic bromides, such as naphthyl (E14), indolyl (E15) and
quinolyl (E16) afforded their corresponding -arylative ketones in
moderate yields (3aa-19, 3aa-20 and 3aa-21).
Scheme 3. Aryl bromides as the trapping electrophiles. Reaction conditions: 1)
1a (0.45 mmol), 2a (0.30 mmol), MeLi (0.75 mmol), THF (2.0 mL), -30 oC, 5 min
then 100 oC, 8 h; 2) Ar’Br (0.20 mmol), Pd(dba)2 (3.0 mol%) and DtBuPF (3.6
mol%), 100 oC, 12 h; [a] 1a: 2a: E11 = 1.5:1:1 (0.25 mmol scale). Yields based
on isolated products.
This transformation can be a practical method for directly
converting various carboxylic acids to ketones. With 1a as the
standard and H2O as the trapping electrophile, a broad scope of
aromatic and aliphatic carboxylic acids were tested (Scheme 4).
Functional groups such as p-NMe2, p-OMe, m-OMe, p-F, p-CF3
and 3,5-dichloro were well tolerated and produced their
corresponding ketones 3ba-3ga in good yields. Other aromatic
and heteroaromatic acids like 2-naphthoic acid (3ha), 2-furoic
acid (3ia), N-Me indole-2-carboxylic acid (3ja) and picolinic acid
(3ka) all afforded their ketones in moderate to good yields. An
aromatic diacid, isophthalic acid, generated the desired diketone
3la in 61% yield. Considering that 1,3-diacyl benzene can be
suitable precurors for NCN-type diimine ligands,[10] this method
may diversify the synthesis of those ligands. Aliphatic acids were
smoothly converted to unsymmetrical aliphatic ketones.
Hydrocinnamic acid derivatives gave their corresponding ketones
3ma-3oa in good to excellent yields. Caproic acid was converted
to ketone 3pa in 90% yield. Aliphatic CF3 group was well tolerated
(3qa). Various steric hindered aliphatic acids at -position
proceeded well to generate ketones 3ra-3ua. Only the pivalic acid
afforded its tert-butyl ketone 3ua in a relatively low yield. Recently,
it was reported that C=C bond could react with -monoboryl
carbanion.[5b] While using a 3,3-disubstituted acrylic acid in
current study produced the desired ,-unsaturated ketone 3va
This article is protected by copyright. All rights reserved.

10.1002/anie.201801679
Angewandte Chemie International Edition
COMMUNICATION
in a good yield without observation of reaction at the C=C bond.
Lithocholic acid derivative was converted to its corresponding
ketone 3wa in 55% yield, indicating the potential application of
this method in nature product modifications.
with MeLi showed a peak at 1558 cm-1, which is different from that
in the reaction mixture (1567 cm-1). Moreover, the free PhCOOLi
is slightly soluble in toluene and a suspension was observed.
However, a clear solution was obtained after the addition of MeLi
to the mixture of 1a and 2a (See SI). These phenomena further
indicated the interaction between [PhCOO-] and the activated 1a.
Such a reaction mixture did not proceed further transformation
below room temperature. However, when heating the mixture at
100 oC, the peak at 1567 cm-1 quickly decreased. Meanwhile the
peak at 1558 cm-1 (the same as the free [PhCOO-] absorbance)
appeared and quickly reached to the highest point (Figure 1b),
along with the observation of suspension in the reaction mixture.
This peak quickly decreased until the completion of the reaction.
Those observations suggested the release of [PhCOO-] from a
complex and further being consumed at high temperature.
Figure 1. The 3D FTIR profile of the reaction of 1a (0.75 mmol), 2a (0.50 mmol),
MeLi (1.25 mmol) in toluene (3.0 mL).
Based on those results, a tentative reaction pathway was
proposed in Scheme 5. The initial interaction between 1a and 2a
generated a complex I-1. Upon the addition of MeLi, acidic proton
in I-1 was removed and one of the boron centers was coordinated
by Me group to give species I-2. Heating the reaction mixture at
100 oC promoted the generation of reactive -monoboryl
carbanion species I-4 from I-2 by releasing carboxylate I-3. Then,
the interaction of I-4 with the carbonyl of I-3 via I-5 generated the
desired enolate 3aa-en. The release of active -monoboryl
carbanion I-4 from its masked form I-2 is necessary for its
reaction with carboxylate. Then, electrophilic trapping of 3aa-en
achieves various di-functionalization of 1,1-diborylalkanes.
Scheme 4. Substrate scope of carboxylic acids and 1,1-diborylalkanes with H2O
as the trapping electrophile. Reaction conditions: 1) 2 (0.25 mmol), 1a (0.375
mmol), MeLi (0.625 mmol), toluene (2.0 mL), -30 oC, 5 min then 100 oC, 8 h; 2)
Quenched by H2O. Yields based on isolated products. [a] 1a (0.75 mmol) and
MeLi (1.0 mmol), THF, 24 h.
Then, several other 1,1-diborylalkanes were further tested
(Scheme 4, 3bb-3bg). These 1,1-diborylalkanes were easily
accessed by our recent development on the gem-diborylation of
aldehydes and ketones.[2j] Picolinic acid was applied as the
coupling partner to exhibit the advantage of this method on the
synthesis of various electron-deficient aromatic ketones. Both
terminal and non-terminal 1,1-diborylalkanes were suitable for
this transformation and afforded the desired products in moderate
to good yields (3bb, 3bc, 3bd, 3be, 3bf and 3bg).
To get insightful information of this transformation, the mixture
of 1a and 2a in toluene was monitored by in-situ IR spectroscopy
(Figure 1). From IR spectra, 2a has a characteristic peak at 1696
cm-1. 1a has no specific absorbance at the region from 1650 to
1750 cm-1 (See spectra in SI). However, when 1a was added, the
absorbance of 2a at 1696 cm-1 decreased to a certain extent and
a new peak at 1728 cm-1 immediately appeared (Figure 1a). This
observation indicated that there is interaction between 1a and 2a.
We deduced that the interaction may be caused by the
coordination of acid oxygens to the boron centers of 1a. Upon the
addition of MeLi, the methide will first remove the acidic proton
and then coordinate to boron. When MeLi was added, the peaks
at 1696 cm-1 and 1728 cm-1 decreased immediately, meanwhile a
new peak at 1567 cm-1 increased immediately (Figure 1a and 1b),
which was assigned to be the featured absorbance of [PhCOO-].
However, the free PhCOOLi by deprotonation of PhCOOH (2a)
Scheme 5. Proposed reaction pathway
In summary, we have developed a dual functionalization of 1,1-
diborylalkanes via deoxygenative enolization with carboxylic
acids followed by electrophilic trapping strategy. MeLi was applied
to activate 1,1-diborylalkanes, in which -monoboryl carbanion
was generated as the active species. Various -mono, di- and tri-
substituted ketones were obtained. In-situ IR spectroscopy
exhibited the interaction between carboxylic acid and 1,1-
diborylalkane. The release of active -monoboryl carbanion from
This article is protected by copyright. All rights reserved.

10.1002/anie.201801679
Angewandte Chemie International Edition
COMMUNICATION
[4] a) D. S. Matteson, R. J. Moody, Organometallics 1982, 1, 20-28; b) K. Endo,
M. Hirokami, T. Shibata, J. Org. Chem. 2010, 75, 3469-3472; c) E. Kohei,
S. Akira, O. Takahiro, S. Takanori, Chem. Lett. 2011, 40, 1440-1442; d) J.
R. Coombs, L. Zhang, J. P. Morken, Org. Lett. 2015, 17, 1708-1711; e) E.
La Cascia, A. B. Cuenca, E. Fernández, Chem. Eur. J. 2016, 22, 18737-
18741; f) T. C. Stephens, G. Pattison, Org. Lett. 2017, 19, 3498-3501.
[5] a) J. Park, S. Choi, Y. Lee, S. H. Cho, Org. Lett. 2017, 19, 4054-4057; b)
X. Liu, T. M. Deaton, F. Haeffner, J. P. Morken, Angew. Chem. Int. Ed.
2017, 56, 11485-11489; c) J. Kim, K. Ko, S. H. Cho, Angew. Chem. Int. Ed.
2017, 56, 11584-11588; d) C. Hwang, W. Jo, S. H. Cho, Chem. Commun.
2017, 53, 7573-7576; e) Z.-Q. Zhang, B. Zhang, X. Lu, J.-H. Liu, X.-Y. Lu,
B. Xiao, Y. Fu, Org. Lett. 2016, 18, 952-955; f) M. Zhan, R.-Z. Li, Z.-D. Mou,
C.-G. Cao, J. Liu, Y.-W. Chen, D. Niu, ACS Catal. 2016, 6, 3381-3386; g)
B. Potter, E. K. Edelstein, J. P. Morken, Org. Lett. 2016, 18, 3286-3289; h)
J. Park, Y. Lee, J. Kim, S. H. Cho, Org. Lett. 2016, 18, 1210-1213; i) S. A.
Murray, J. C. Green, S. B. Tailor, S. J. Meek, Angew. Chem., Int. Ed. 2016,
55, 9065-9069; j) J. Kim, S. Park, J. Park, S. H. Cho, Angew. Chem., Int.
Ed. 2016, 55, 1498-1501; k) W. Jo, J. Kim, S. Choi, S. H. Cho, Angew.
Chem., Int. Ed. 2016, 55, 9690-9694; l) S. Xu, X. Shangguan, H. Li, Y.
Zhang, J. Wang, J. Org. Chem. 2015, 80, 7779-7784; m) M. V. Joannou, B.
S. Moyer, S. J. Meek, J. Am. Chem. Soc. 2015, 137, 6176-6179; n) M. V.
Joannou, B. S. Moyer, M. J. Goldfogel, S. J. Meek, Angew. Chem., Int. Ed.
2015, 54, 14141-14145; o) Z.-Q. Zhang, C.-T. Yang, L.-J. Liang, B. Xiao,
X. Lu, J.-H. Liu, Y.-Y. Sun, T. B. Marder, Y. Fu, Org. Lett. 2014, 16, 6342-
6345; p) C. Sun, B. Potter, J. P. Morken, J. Am. Chem. Soc. 2014, 136,
6534-6537; q) B. Potter, A. A. Szymaniak, E. K. Edelstein, J. P. Morken, J.
Am. Chem. Soc. 2014, 136, 17918-17921; r) H. Li, Z. Zhang, X. Shangguan,
S. Huang, J. Chen, Y. Zhang, J. Wang, Angew. Chem., Int. Ed. 2014, 53,
11921-11925; s) K. Hong, X. Liu, J. P. Morken, J. Am. Chem. Soc. 2014,
136, 10581-10584; t) K. Endo, T. Ohkubo, T. Ishioka, T. Shibata, J. Org.
Chem. 2012, 77, 4826-4831; u) K. Endo, T. Ohkubo, T. Shibata, Org. Lett.
2011, 13, 3368-3371; v) K. Endo, T. Ohkubo, M. Hirokami, T. Shibata, J.
Am. Chem. Soc. 2010, 132, 11033-11035.
its masked form was necessary for its reaction with carboxylate to
afford enolate species.
Acknowledgements
This work was supported by the NNSFC (91745110, 21673261,
21603245, 21633013 and 21703265) and a Start-up funding from
LICP. Support from the Young Elite Scientist Sponsorship
Program by CAST, CAS Interdisciplinary Innovation Team, the
Key Program of CAS (QYZDJ-SSW-SLH051), the Youth
Innovation Promotion Association CAS (2018458) and the ‘Light
of West China’ Program were also acknowledged.
Keywords: 1,1-diborylalkane • Carboxylic acid • Boron enolate •
Ketone synthesis • -Monoboryl Carbanion
[1] a) D. G. Hall, H. Lachance, Allylboration of carbonyl compounds, Wiley,
Hoboken, NJ, 2012; b) D. G. Hall, Boronic Acids: Preparation and
Applications in Organic Synthesis, Medicine and Materials, Vol. 1 and 2,
2nd ed., Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim, Germany,
2011; c) N. Miyaura, A. Suzuki, Chem. Rev. 1995, 95, 2457-2483; d) E. C.
Neeve, S. J. Geier, I. A. I. Mkhalid, S. A. Westcott, T. B. Marder, Chem.
Rev. 2016, 116, 9091-9161.
[2] a) H. Abu Ali, I. Goldberg, M. Srebnik, Organometallics 2001, 20, 3962-
3965; b) H. Abu Ali, I. Goldberg, D. Kaufmann, C. Burmeister, M. Srebnik,
Organometallics 2002, 21, 1870-1876; c) V. M. Dembitsky, H. Abu Ali, M.
Srebnik, Appl. Organomet. Chem. 2003, 17, 327-345; d) D. S. Matteson, R.
J. Moody, J. Am. Chem. Soc. 1977, 99, 3196-3197; e) L. Li, T. Gong, X. Lu,
B. Xiao, Y. Fu, Nat. Commun. 2017, 8, 345; f) K. Endo, M. Hirokami, T.
Shibata, Synlett 2009, 1331-1335; g) Z. Zuo, Z. Huang, Org. Chem. Front.
2016, 3, 434-438; h) S. Lee, D. Li, J. Yun, Chem. Asian J. 2014, 9, 2440-
2443; i) H. Li, X. Shangguan, Z. Zhang, S. Huang, Y. Zhang, J. Wang, Org.
Lett. 2014, 16, 448-451; j) L. Wang, T. Zhang, W. Sun, Z. He, C. Xia, Y.
Lan, C. Liu, J. Am. Chem. Soc. 2017, 139, 5257-5264; k) T. C. Atack, S. P.
Cook, J. Am. Chem. Soc. 2016, 138, 6139-6142; l) J. C. H. Lee, R.
McDonald, D. G. Hall, Nat. Chem. 2011, 3, 894-899; m) X. Feng, H. Jeon,
J. Yun, Angew. Chem., Int. Ed. 2013, 52, 3989-3992; n) W. N. Palmer, J.
V. Obligacion, I. Pappas, P. J. Chirik, J. Am. Chem. Soc. 2016, 138, 766-
769; o) S. H. Cho, J. F. Hartwig, Chem. Sci. 2014, 5, 694-698; p) W. N.
Palmer, C. Zarate, P. J. Chirik, J. Am. Chem. Soc. 2017, 139, 2589-2592.
[3] R. Nallagonda, K. Padala, A. Masarwa, Org. Biomol. Chem. 2018, 16,
1050-1064.
[6] a) D. S. Matteson, K. Arne, J. Am. Chem. Soc. 1978, 100, 1325-1326; b)
D. S. Matteson, D. Majumdar, Organometallics 1983, 2, 230-236; c) A.
Pelter, L. Warren, J. W. Wilson, Tetrahedron 1993, 49, 2888-3006; d) T.
Mukaiyama, M. Murakami, T. Oriyama, M. Yamaguchi, Chem. Lett. 1981,
10, 1193-1196.
[7] C. E. Iacono, T. C. Stephens, T. S. Rajan, G. Pattison, J. Am. Chem. Soc.
2018, 140, 2036-2040.
[8] H. C. Brown, S. P. Rhodes, J. Am. Chem. Soc. 1969, 91, 4306-4307.
[9] D. U. Nielsen, C. Lescot, T. M. Gøgsig, A. T. Lindhardt, T. Skrydstrup,
Chem. Eur. J. 2013, 19, 17926-17938.
[10] M. Stol, D. J. M. Snelders, M. D. Godbole, R. W. A. Havenith, D. Haddleton,
G. Clarkson, M. Lutz, A. L. Spek, G. P. M. van Klink, G. van Koten,
Organometallics 2007, 26, 3985-3994.
This article is protected by copyright. All rights reserved.

10.1002/anie.201801679
Angewandte Chemie International Edition
COMMUNICATION
COMMUNICATION
Wei Sun, Lu Wang, Chungu Xia,* and
Chao Liu*
Page No. – Page No.
Dual Functionalization of α-
Monoboryl Carbanion via A
Deoxygenative Enolization with
Carboxylic Acids
Dual functionalization of 1,1-diborylalkanes via a deoxygenative enolization with
carboxylic acids as the acylative synthon followed by electrophilic trapping strategy
was developed for the first time. -Monoboryl carbanion was generated as the active
species by activation of 1,1-diborylalkanes with methyllithium. A variety of carboxylic
acids, 1,1-diborylalkanes and electrophiles were demonstrated to selectively afford
-mono, di- and tri-substituted ketones. In-situ IR spectroscopy studies exhibited the
interaction between carboxylic acid and 1,1-diborylalkane before adding activation
reagent. The release of active -monoboryl carbanion from its masked form is
necessary for the reaction with carboxylate to afford enolate species.
This article is protected by copyright. All rights reserved.