Br?nsted Base-Mediated Regio- and Stereoselective trans-Silaboration of Propargylamides: Access to 1,2-Vinylborasilanes

Article abstract of DOI:10.1002/chem.201703774

A facile method for the preparation of β-boryl-α-silyl aryl acrylamides using phenyllithium, dimethylphenylsilylpinacolborane, and propargylamides is reported. A key feature of this transition metal-free reaction is the Br?nsted base deprotonation of aryl secondary propargylamide to produce a Lewis base that activates the B?Si bond, which is followed by a sequential intramolecular α-silylation-trans-β-borylation. The reaction proceeds in complete regio- and stereoselectivity. A wide variety of N- and aryl-substituted propargylamides afford trans-1,2-vinylborasilanes in high yield. The vicinal borasilane products undergo a variety of subsequent chemoselective transformations.

Full text of DOI:10.1002/chem.201703774

A Journal of
Accepted Article
Title: Brønsted Base Mediated Regio- and Stereoselective trans
Silaboration of Propargylamides: Access to 1,2-Vinylborasilanes
Authors: Russell Fritzemeier and Webster L Santos
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: Chem. Eur. J. 10.1002/chem.201703774
Link to VoR: http://dx.doi.org/10.1002/chem.201703774
Supported by

10.1002/chem.201703774
Chemistry - A European Journal
FULL PAPER
Brønsted Base Mediated Regio- and Stereoselective trans
Silaboration of Propargylamides: Access to 1,2-Vinylborasilanes
Russell Fritzemeier[a] and Webster L. Santos[a]
Abstract: A facile method for the preparation of β-boryl-α-silyl aryl
and
Sawamura
Ohmiya
acrylamides using phenyllithium, dimethylphenylsilylpinacolborane,
and propargylamides is reported. A key feature of this transition
metal-free reaction is the Brønsted base deprotonation of aryl
secondary propargylamide to produce a Lewis base that activates
the B-Si bond, which is followed by a sequential intramolecular α
silylation-trans β borylation. The reaction proceeds in complete
regio- and stereoselectivity. A wide variety of N- and aryl substituted
propargylamides afford trans 1,2-vinylborasilanes in high yield. The
O
O
Bpin
PhMe2Si
cat. PBu3
Bpin
neat
OEt
R
OEt
SiMe2Ph
,
R
80 °C, 8 h
PhMe2Si
O
via:
B
O
Bu3P
O
OEt
•
R
vicinal borasilane products undergo
chemoselective transformations.
a variety of subsequent
neat
Bpin
O
cat. PBu3
,
O
Bpin
80 °C
NHMe
x
Ar
NHMe
SiMe2Ph
Ar
PhMe2Si
Introduction
Nishihara
Ph
PhMe2Si
PhMe2Si
PdCl
Bpin
Bpin
Bpin
Vinylboronic acids and vinylsilanes are a special class of
functional groups capable of undergoing variety of
Ph
Bpin
KOH
a
2(dppf),
rt, 3 h
transformations through Suzuki-Miyaura and Hiyama coupling
reactions among many.[1] Further, they have demonstrated utility
in medicinal chemistry as key synthetic intermediates[2] as well
as essential features in pharmacophores[3]. Thus, methods for
their synthesis are essential. The concurrent installation of boron
and silicon moieties into alkynes affords the most direct and
atom economical process to access these products.[4] For
example, a handful transition metal catalysts such as Pd,[5] Pt,[5a]
and Au[6] efficiently react with terminal and internal alkynes to
exclusively afford cis products. In sharp contrast, synthetic pro-
tocols to afford trans addition products are scarce. Recently,
Sawamura and Ohmiya elegantly reported an organocatalytic
silaboration of acetylenic esters (Scheme 1).[7] Their method
employed tributylphosphine, which upon 1,4-addition to the
acetylenic ester generates a Lewis basic allenolate that forms a
Suzuki-Miyaura
Ph
Bpin
Ar
PhMe2Si
work
this
O
O
Bpin
PhMe2Si
Bpin
NHMe
Ar
NHMe
Ar
SiMe2Ph
PhLi, 12-crown-4
60 °C, 30 min
trans
product
exclusively
O
O
O
:
via
B
PhMe2Si
NMe
Ar
complex
with
Suginome’s
borosilane
reagent
8]
[dimethylphenylsilylpinacolborane (pinBSiMe2Ph)])[4,
resulting
in a trans and regioselective addition of boryl and silyl
functionalities across the triple bond. However, the protocol is
limited to acetylenic esters, requires elevated temperature, and
long reaction times. Alternatively, Nishihara and co-workers
employed a palladium catalysed silaboration of alkynylboronate
Scheme 1. Approaches to trans 1,2-vinylborasilanes.
Transition metal-mediated introduction of boryl and silyl
groups on alkenes to afford geminal borasilanes have been
reported.[9] Interestingly, the complementary metal-free
silaborations involving activation of the Si-B bond through
pyramidalization of boron have been disclosed for alkenes,[10]
allenes,[11] and hydrazones.[12] Inspired by these and our
investigations on the corresponding trans diboration of alkynes,
we surmised that a metal-free silaboration is propargylamides
possible.[13] We hypothesized that a Brønsted base could
faciliate the deprotonation of propargylamides to form a Lewis
to
form
1-phenyl-1-silyl-2,2-diborylethene,
which
chemoselectively underwent a Suzuki-Miyaura cross coupling
reaction to yield trans 1,2-vinylborasilane.[2] Notwithstanding the
merit of developing economical and environmentally friendly
reaction conditions, methods for the preparation of trans 1,2-
vinylborasilanes are needed.
[a]
R. Fritzemeier and Prof. Dr. W. L. Santos
Department of Chemistry
Virginia Tech
acid-base complex, transferring silicon to the
α carbon
900 West Campus Drive, Blacksburg, VA 24061 (USA)
E-mail: santosw@vt.edu
regioselectively, and intramolecularly trapping Bpin to afford the
desired trans 1,2-vinylborasilanes (Scheme 1). Interestingly,
such a proposal is mechanistically distinct from the method
developed by Sawamura and Ohmiya. Herein, we disclose a
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/chem.201703774
Chemistry - A European Journal
FULL PAPER
novel transition-metal free Brønsted base-mediated reaction of
Suginome’s reagent with propargylamides to afford β-boryl-α-
silylacrylamides.
13
O
O
B
O
Results and Discussion
NHMe
Ph
SiMe2
We initiated our studies using conditions previously de-
veloped for alkyne diboration.[13] Unfortunately, treating N-methyl
phenylpropiolamide (2a) with NaH in the presence of crown
ether failed to generate the desired product 3a (entry 1, Table 1).
Other bases such as LiH, NaOMe, NaOAc, NaHMDS were also
inefficient in yielding 3a (entries 2-5). To our delight, switching to
an organolithium base such as n-BuLi in THF afforded 3a in
60% yield (entry 6). Performing the reaction in solvents such as
toluene, 1,4-dioxane and tert-butylmethyl ether was less
effective (entries 7-9). Removing the chelating agent (12-crown-
4) severely decreased the reaction yield, highlighting the im-
portance of a naked anion utilized to activate the B-Si bond.
Other
50
45
40
35
30
25
20
f1 (ppm)
15
10
5
0
-5
-10
Figure 1. 11B NMR of 3a.
organolithiums resulted in a slight increase in reaction yield
and PhLi proved to be the best (entries 11-12). Neither a
Grignard reagent nor DBU was successful. Fortunately,
under the optimized reaction conditions (entry 12), the
reaction is complete within 30 min. 11B NMR analysis of 3a
revealed a tetrahedral coordination on boron, suggesting
the trans configuration between the boryl and silyl groups
(Figure 1).
With optimized reaction conditions in hand (entry 12), a
variety of aryl substituted propargylamides were screened to
determine substrate scope and limitations (Table 2). Aryl
substituted propargylamides containing alkyl groups (2b-2d) at
varying positions as well as steric size afforded silaborated
products 3b-3d in moderate to good yields. However, when a
sterically encumbered mesityl group (2e) was used, the reaction
was inefficient possibly as a result of steric class with the
incoming borylsilane reagent. Gratifyingly, a more electron-
donating methoxy group either on the para (2f) or ortho (2g)
position performed moderately well generating the products in
~50% yield. Electron with drawing substituents were equally
efficient substrates. For example, chloro substitution at the ortho
(2h) or para (2i) position affording 3h-i in 65% yields.
Trifluoromethyl (2j) or difluoro (2k) groups resulted in slightly
diminished yields while a cyano moiety (2l) gave a 32% yield,
Table 1. Reaction Optimization[a]
O
O
Bpin
PhMe2Si
Bpin
NHMe
NHMe
base, solvent,
chelating
60 °C, 30 min
Ph
agent
SiMe2
2a
Base
NaH
LiH
3a
Entry
1
Solvent
THF
Crown ether
Yield[b]
15-crown-5
12-crown-4
15-crown-5
15-crown-5
15-crown-5
12-crown-4
12-crown-4
12-crown-4
12-crown-4
-
0
2
THF
0
3
NaOMe
NaOAc
NaHMDS
nBuLi
nBuLi
nBuLi
nBuLi
nBuLi
MeLi
THF
0
4
THF
0
5
THF
0
6
THF
60
23
50
Trace
21
63
67
0
7
Toluene
Dioxane
TBME
THF
8
likely as
a complication of butyllithium reacting with the
9
benzonitrile. Other aryl groups such as thiophene (2m) and
naphthalene (2n) were also tolerated, albeit in moderate yields.
Unfortunately, an alkyl substituted propargylamide (2o) was
unable to undergo this transformation presumably due to the
lack of delocation of electrons from the resulting carbanionic
intermediate. Finally, protecting groups such as benzyl (2p),
methoxymethylether (2q) and allyl (2r) generated silaborated
products in good yields.
We next turned our attention to investigating the effect of N-
substitutions on the propargylamides (Table 3). Under the same
reaction conditions, secondary propargylamides reacted
smoothly toward substrates with high steric demand (i.e.,
isopropyl 4a). Benzyl (4b) as well as phenyl (4c) groups were
well tolerated to produce the products in up to 66% yield. The
10
11
12
13
14
THF
12-crown-4
12-crown-4
-
PhLi
THF
EtMgBr
DBU
THF
THF
-
0
[a] General procedure: propargylamide (1 equiv.), base (1.4 equiv.), and
crown ether (1.4 equiv.) dissolved in THF (0.3M) at -78 °C for 15 min.
pinBSiMe2Ph (1.4 equiv.) was added dropwise and allowed to warm to rt.
Reaction was then heated to 60 °C for 30 min. [b] Isolated yields.
This article is protected by copyright. All rights reserved.

10.1002/chem.201703774
Chemistry - A European Journal
FULL PAPER
Table 2. Aryl substituted N-methyl propargylamides[a]
Table 3. N-substituted phenyl propargylamides[a]
O
O
PhMe2Si
Bpin
PhLi, THF
B
O
pin
Ar
B
O
pin
PhMe2Si
Bpin
NHMe
NHR
NHMe
NHR
Z
(
)-exclusive
12-crown-4
min
PhLi, THF
12-crown-4
60 °C, 30 min
Ar
SiMe2Ph
60 °C, 30
SiMe2Ph
2b-q
3b-r
4a-e
5a-e
B
O
pin
Entry
1
Substrate
Product
O
Yield (%)[b]
B
O
B
O
pin
pin
Me
NHMe
SiMe2Ph
NHMe
SiMe2Ph
B
B
NHMe
SiMe2Ph
pin
O
t-Bu
n
-Bu
N
H
69
3c
3b
(59%)
3d
N
H
(69%)
(55%)
SiMe2Ph
5a
Ph
Ph
4a
B
O
MeO pin
B
O
B
O
Me
pin
pin
O
pin
O
NHMe
NHMe
SiMe2Ph
NHMe
SiMe2Ph
2
3
4
5
6
66
47
57
44[c]
0
NHBn
SiMe2Ph
NHBn
NHPh
MeO
SiMe2
Ph
Me
Me
3g
4b
5b
(49%)
3f
3e
(47%)
(0%)
B
O
pin
pin
B
O
pin
B
pin
O
O
Cl
B
pin
O
NHPh
SiMe2Ph
5c
NHMe
SiMe2Ph
NHMe
NHMe
SiMe2Ph
SiMe2Ph
Ph
Ph
4c
Cl
F3C
b
3i
(66%)
3j
3h
(44%)
(64%)
B
O
O
N
H
B
O
pin
N
H
B
pin
O
SiMe2Ph
5d
F
NHMe
4d
NHMe
SiMe2Ph
SiMe2Ph
NC
O
B
B
O
pin
F
3k
3l
(40%)
(32%)
O
NH2
SiMe2Ph
5e
NH2
B
O
pin
B
O
B
Ph
Ph
pin
4e
pin
NHMe
SiMe2Ph
NHMe
SiMe2Ph
(37%)
NHMe
SiMe2Ph
S
O
pin
O
3o
(0%)
3n
3m
(30%)
NMe2
SiMe2Ph
5f
NMe2
4f
B
O
B
O
pin
B
O
pin
pin
NHMe
SiMe2Ph
NHMe
SiMe2Ph
NHMe
[a] Reaction conditions: propargylamide (1 equiv.), phenyllithium (1.4 equiv.),
and 12-crown-4 (1.4 equiv.) were dissolved in THF (0.3M) at -78 °C for 15 min.
pinBSiMe2Ph (1.4 equiv.) was added dropwise and allowed to warm to rt.
Reaction was then heated to 60 °C for 30 min. [b] Isolated yields. [c] 1.5
equiv. phenyllithium used.
SiMe2Ph
O
MOMO
BnO
3p
3r
3q
(45%)
(45%)
(40%)
[a] Reaction conditions: propargylamide (1 equiv.), phenyllithium (1.4 equiv.),
and 12-crown-4 (1.4 equiv.) were dissolved in THF (0.3M) at -78 °C for 15 min.
pinBSiMe2Ph (1.4 equiv.) was added dropwise and allowed to warm to rt.
Reaction was then heated to 60 °C for 30 min. [b] 1.8 equiv. phenyllithium
used.
Me
Me
,
KOH
4
Pd(PPh3)
NaOMe, Br2
3a
O
4-bromotoluene
THF, rt, 16 h
73%
rt
to
O
-78
DCM,
°C
95%
Ph
NHMe
reaction condition also demonstrated chemoselective reactivity
in the presence of allylamide (4d) to generate a highly
functionalized allylamide 5d. Furthermore, an electronically
deactivated primary amide (4e) acted as an efficient substrate.
As expected, tertiary amide 4f was unreactive. This result, along
with the necessity for a chelating agent such as a crown ether,
supports our mechanistic proposal that a strong Lewis base
generated by a naked anion is needed to activate Suginome’s
reagent and facilitate the silaboration process. Consistent with
3a, 11B NMR of all 1,2-vinylborasilane products show a single
peak at 10-15 ppm indicative of internal coordination of the
Ph
NHMe
Ph
SiMe2
Br
6
7
NHMe
O
OMe
TEA
2, CuI,
Pd(dppf)Cl
Me
THF, rt,
36
h
Ph
4-ethynylanisole,
45%
8
O
O
Oxone, AcOH
3a
Ph
NHMe
rt, 5 min
82%
9
carbonyl oxygen with
a
tetrahedral boron atom (see
supplemental information for details).
Scheme 2. Synthetic application and transformations of 3a.
To demonstrate the utility of trans 1,2-vinylborasilanes, we
subjected compound 3a to several chemical transformations
(Scheme 2). Under standard Suzuki-Miyaura cross-coupling
conditions, 3a chemoselectively reacts to install the tolyl group
on the beta carbon, affording 6 in 73% yield. In the presence of
This article is protected by copyright. All rights reserved.

10.1002/chem.201703774
Chemistry - A European Journal
FULL PAPER
sodium methoxide and bromine, bromodesilylation occurred in
95% yield to form vinyl bromide 7. Subsequent Sonogashira
cross coupling conditions using Pd(dppf)Cl2 and 4-
Acknowledgements
We acknowledge financial support by the National Science
Foundation (CHE-1414458).
ethynylanisole at room temperature afforded
a
densely
substituted alkene 8 bearing a highly conjugated enyne moiety;
this is a product that is previously inaccessible. In addition, 3a
underwent rapid oxidation and desilylation within minutes to
generate β-ketoamide 9. β-ketoamides are key intermediates in
the synthesis of dipeptidyl peptidase IV inhibitor, Sitaligpin
(Januvia), which is an FDA approved drug for the treatment of
Type 2 diabetes mellitus.[14]
Keywords: chemoselectivity • diastereoselectivity • synthetic
methods • boron • silicon
[1]
a) A. Barbero, F. J. Pulido, Acc. Chem. Res. 2004, 37, 817-825; b) I.
Fleming, R. Henning, D. C. Parker, H. E. Plaut, P. E. J. Sanderson, J.
Chem. Soc. Perkin Trans. 1 1995, 317-337; c) K. Tamao, N. Ishida, T.
Tanaka, M. Kumada, Organometallics 1983, 2, 1694-1696; d) A. J. J.
Lennox, G. C. Lloyd-Jones, Chem. Soc. Rev. 2014, 43, 412-443; e) N.
Miyaura, A. Suzuki, Chem. Rev. 1995, 95, 2457-2483; f) S. E. Denmark,
J. H. C. Liu, Angew. Chem. Int. Ed. 2010, 49, 2978-2986; Angew.
Chem. 2010, 122, 3040-3049; g) Y. Nakao, T. Hiyama, Chem. Soc.
Rev. 2011, 40, 4893-4901.
Conclusions
In conclusion, we have developed a novel Brønsted base-
mediated silaboration method that exclusively affords (Z)-α-silyl-
β-boryl acrylamides in a manner that is both mild and transition
metal-free. The installation of the boryl and silyl group in a trans
fashion is achieved through Lewis acid-base adduct formation
[2]
[3]
J. Jiao, K. Nakajima, Y. Nishihara, Org. Lett. 2013, 15, 3294-3297.
a) A. Adamczyk-Woźniak, O. Komarovska-Porokhnyavets, B.
Misterkiewicz, V. P. Novikov, A. Sporzyński, Appl. Organomet. Chem.
2012, 26, 390-393; b) B. A. Teicher, G. Ara, R. Herbst, V. J. Palombella,
J. Adams, Clin. Cancer Res. 1999, 5, 2638-2645; c) E. Sonoiki, C. L.
Ng, M. C. S. Lee, D. Guo, Y.-K. Zhang, Y. Zhou, M. R. K. Alley, V.
Ahyong, L. M. Sanz, M. J. Lafuente-Monasterio, C. Dong, P. G. Schupp,
J. Gut, J. Legac, R. A. Cooper, F.-J. Gamo, J. DeRisi, Y. R. Freund, D.
A. Fidock, P. J. Rosenthal, Nat. Commun. 2017, 8, 14574.
with Suginome’s reagent and sequential intramolecular
α
silylation-β borylation. A wide variety of N- and aryl substitutions
are tolerated with products being indefinitely stable to air at
ambient conditions. The utility of 1,2-vinylborasilanes is
demonstrated by chemoselective cross-coupling reactions and
subsequent chemical transformations.
[4]
[5]
M. Oestreich, E. Hartmann, M. Mewald, Chem. Rev. 2013, 113, 402-
441.
a) M. Suginome, T. Matsuda, H. Nakamura, Y. Ito, Tetrahedron 1999,
55, 8787-8800; b) M. B. Ansell, J. Spencer, O. Navarro, ACS Catal.
2016, 6, 2192-2196; c) T. Ohmura, K. Oshima, H. Taniguchi, M.
Suginome, J. Am. Chem. Soc. 2010, 132, 12194-12196; d) M.
Suginome, H. Nakamura, Y. Ito, Chem. Commun. 1996, 2777-2778; e)
H. N. M. Suginome, T. Hasui, M. Murakami, Bull. Chem. Soc. Jpn. 2005,
78, 323-326; f) J. Carlos Araujo Da Silva, M. Birot, J.-P. Pillot, M.
Pétraud, J. Organomet. Chem. 2002, 646, 179-190; g) S.-y. Onozawa,
Y. Hatanaka, M. Tanaka, Chem. Commun. 1997, 1229-1230; h) T.
Ohmura, K. Oshima, M. Suginome, Chem. Commun. 2008, 1416-1418.
C. Gryparis, M. Stratakis, Org. Lett. 2014, 16, 1430-1433.
Experimental
General procedure
Under nitrogen atmosphere, a solution of propargylamide (1
equiv.) and 12-crown-4 (1.4 equiv.) in THF at -78 °C was added
phenyllithium (1.4 equiv.) dropwise and stirred at -78 °C for 15
min. The borosilane (pinBSiMe2Ph, 1.4 equiv) was then added
dropwise and the solution was allowed to warm to rt, then
heated to 60 °C for 30 min. The reaction mixture was
concentrated in vacuo and subsequently purified by column
chromatography using a 10-40% gradient of ethyl acetate in
DCM to yield the desired product.
[6]
[7]
[8]
[9]
K. Nagao, H. Ohmiya, M. Sawamura, Org. Lett. 2015, 17, 1304-1307.
M. Suginome, T. Matsuda, Y. Ito, Organometallics 2000, 19, 4647-4649.
a) M. Suginome, H. Nakamura, Y. Ito, Angew. Chem. Int. Ed. 1997, 36,
2516-2518; Angew. Chem. 1997, 109, 2626-2628; b) M. Gerdin, M.
Penhoat, R. Zalubovskis, C. Pétermann, C. Moberg, J. Organomet.
Chem. 2008, 693, 3519-3526; c) M. Suginome, T. Matsuda, T.
Yoshimoto, Y. Ito, Org. Lett. 1999, 1, 1567-1569; d) M. Suginome, T.
Matsuda, T. Yoshimoto, Y. Ito, Organometallics 2002, 21, 1537-1539.
(Z)-2-(dimethyl(phenyl)silyl)-N-methyl-3-phenyl-3-(4,4,5,5-
tetramethyl-1,3,2-dioxaborolan-2-yl)acrylamide
(3a):
[10] a) H. Ito, Y. Horita, E. Yamamoto, Chem. Commun. 2012, 48, 8006-
8008; b) T. Kurahashi, T. Hata, H. Masai, H. Kitagawa, M. Shimizu, T.
Hiyama, Tetrahedron 2002, 58, 6381-6395.
propargylamide (50 mg, 0.31 mmol); phenyllithium (230 µL, 0.44
mmol); pinBSiMe2Ph (120 µL, 0.44 mmol); 12-crown-4 (71 µL,
0.44 mmol). White solid; 1H NMR (400 MHz, CDCl3) δ 7.56-7.51
(m, 2H), 7.46-7.39 (m, 3H), 7.34-7.28 (m, 2H), 7.25-7.20 (m, 3H),
5.60 (brs, 1H), 2.70 (d, J = 5.2, 3H), 1.05 (s, 12H), 0.11 (s, 6H).
13C NMR (100 MHz, CDCl3) δ 177.9, 141.8, 137.5, 134.3, 130.6,
129.6, 129.0, 127.4, 126.6, 125.7, 80.3, 28.7, 25.4, -1.27. 11B
NMR (128 MHz, CDCl3) δ 13.0. HRMS: (ESI) [M+H]+ calc for
C24H33BNO3Si, 422.2323, observed, 422.2313.
[11] M. Shimizu, T. Kurahashi, H. Kitagawa, T. Hiyama, Org. Lett. 2003, 5,
225-227.
[12] H. Li, X. H. Shangguan, Z. K. Zhang, S. Huang, Y. Zhang, J. B. Wang,
Org. Lett. 2014, 16, 448-451.
[13] A. Verma, R. F. Snead, Y. Dai, C. Slebodnick, Y. Yang, H. Yu, F. Yao,
W. L. Santos, Angew. Chem. Int. Ed. 2017, 56, 5111; Angew. Chem.
2017, 129, 5193.
[14] K. B. Hansen, Y. Hsiao, F. Xu, N. Rivera, A. Clausen, M. Kubryk, S.
Krska, T. Rosner, B. Simmons, J. Balsells, N. Ikemoto, Y. Sun, F.
Spindler, C. Malan, E. J. J. Grabowski, J. D. Armstrong, J. Am. Chem.
Soc. 2009, 131, 8798-8804.
This article is protected by copyright. All rights reserved.

10.1002/chem.201703774
Chemistry - A European Journal
FULL PAPER
Entry for the Table of Contents (Please choose one layout)
FULL PAPER
Author(s), Corresponding Author(s)*
•
•
•
•
O
PhMe
PhLi, THF
2Si
Bpin
B
O
trans exclusive
transition metal free
pin
Ar
Page No. – Page No.
NHR
NHR
and
chemo-
wide substrate
regioselective
scope
12-crown-4
60 °C, 30 min
Ar
Ph
SiMe2
Brønsted Base Mediated Regio- and
Stereoselective trans Silaboration of
Propargylamides: Access to 1,2-
Vinylborasilanes
Complexation is the trick: Substrate-assisted Lewis acid-base interaction leads to
trans silaboration in complete regio- and chemoselectivity. Intramolecular B-O
coordination in the products afford highly stabile and effective substrates for
subsequent reactions.
This article is protected by copyright. All rights reserved.