Metal catalyst-free photo-induced alkyl C-O bond borylation

Article abstract of DOI:10.1039/d0cc04776g

Metal catalyst free, blue visible light-induced C-O bond borylation of unactivated tertiary alkyl methyl oxalates has been developed to furnish tertiary alkyl boronates. From the secondary alcohols activated with imidazolylthionyl, moderate yields of boronates were attained under standard photo-induced conditions. Preliminary mechanistic studies confirmed the involvement of a (DMF)2-B2cat2 adduct that weakly absorbs light at 437 nm so as to initiate a Bcat radical. A radical-chain process is proposed wherein the alkyl radical is engaged. This journal is

Full text of DOI:10.1039/d0cc04776g

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DOI: 10.1039/D0CC04776G
COMMUNICATION
Metal Catalyst-Free Photo-Induced Alkyl C–O Bond Borylation
Guobin Ma, Changzhou Chen, Sangita Talukdar, Xinluo Zhao, Chuanhu Lei* and Hegui Gong*
Received 00th January 20xx,
Accepted 00th January 20xx
DOI: 10.1039/x0xx00000x
dehalogenation
A
metal catalsyt free, blue visible light-induced C–O bond
Bpin
pinB
Me
Me
Bpin
Me
Me
borylation of unactivated tertiary alkyl methyl oxalates has been
developed to furnish tertiary alkyl boronates. The secondary
alcohols activated with imidazolylthionyl, moderate yields of the
boronates were attained under the standard photo-induced
Ni, Mn, Cu, Fe, Pd, etc.
R
R
X
X = Cl, Br, I
decarboxylation
Ni, Bpin-Bpin
.
B
45%-68% yields
Me
O
Me
conditions.
Preliminary
mechanistic
studies
confirmed
Me
Bpin
R
O
Me
N
involvement of a (DMF)2–B2cat2 adduct that weakly absorbs light
at 437 nm so as to initiate Bcat radical. A redical-chian process is
proposed wherein alkyl radical is engaged.
R
O
O
1. h, B2cat2
2. Pinacol, Et3N
45%-68% yields
(NPI)
deamination
R
Alkyl boronic acids and esters are an important class of
protease inhibitors and are useful functional groups in
synthetic chemistry.1-4 Tremendous efforts to the preparation
of alkylboronate compounds have been implemented in
particularly by direct coupling of alkyl precursors with diboron
esters.5-15 As such, borylation of alkyl electrophiles catalyzed
by Ni,5-6 Cu,7 Zn,8 Fe,9 Mn10 and Pd11 has witnessed
considerable success. Recently, the less straightforward
borylation methods comprising decarboxylation of carboxylic
N-phthalimidine (NPI) under Ni-catalyzed reductive or photo-
induced conditions have redefined the scope of alkyl
precursors for C–B bond formation.12-13 In the case of photo-
induced conditions, Aggarwal proposed that 2,2'-
bibenzo[d][1,3,2]dioxaborole (B2cat2) in N,N-dimethyl aceta-
mide (DMA) results in two equivalents of boron radical
triggered by photo irradiation. Addition of boron radical to the
carbonyl oxygen of the NPI moiety within the alkyl N-
phthalimidoyl carboxylic ester (Scheme 1) led to subsequent
N–O bond fragmentation and decarboxylation giving an alkyl
radical and CO2. The reaction of alkyl radical with B2cat2
affords the alkyl boronate and a boron radical that recycles in
the reaction process. Following this, similar photo-induced
borylation method has been extended to the substrates of
alkyl iodides and alkyl pyridinium salts, which feature
homolytic scission of C–halide and C–N bonds.14-15 However,
the borylation methods pertains to the cleavage of unactivated
Ph
Lewis base
R
N
BF3K
only example
B2cat2
then KHF2
BF4
Ph
Ph
deoxygenation: Ir-induced C-O bond fragmenation
*IrIII
SET
B cat
2
1.
R3
R3
2
R3
.
O
R2
R2
R1
Ir (cat.)
R2
B-B
blue light/
OMe
2. pinacol
R1
Bpin
O
R1
O
catalyst-free deoxygenation borylation (this work)
.
B
R3
B cat
1.
O
bl2ue li2ght
R2
R3
R2
R1
R3
R2
R1
B-B
OMe
.
O
2. pinacol
Bpin
R1
O
O
B
R3
O
O
R2
R1
R3
OMe
O
.
R2
R1
O
OMe
I
-1
O
O
MeOC(O)CO2Bcat
R3
O
R2
N
O
O
.
B
.
O
h
R1
I
NMe2
O
-2
initiation
H
R2
R3
O
O
O
R1
B
B
O
B
O
O
O
H
NMe2
a. College of Sciences, Center for Supramolecular Chemistry and Catalysis,
Department of Chemistry and Department of Physics, Shanghai
University, 99 Shang-Da Road, Shanghai 200444, China
chlei@shu.edu.cn; Hegui_gong@shu.edu.cn
Scheme 1. Methods for the Formation of Tertiary Alkyl Borates.
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alkyl C–O bonds remains a challenge. Since alcohols are
7
8
9
10
11
12
13c
14e
1/2
1/2
1/2
1/2
1/2.5
1/3
DMI
DMSO
CH3CN
DCE
DMF
DMF
DMF
DMF
30
30
22%
trace
trace
trace
67%
View Article Online
DOI: 10.1039/D0CC04776G
ubiquitous in nature, development of a borylation method
based on easily accessible alcohol derivatives is synthetically
useful and appealing. Recently, we discovered that dialkyl
oxalates derived from tertiary alcohols are amenable for
radical C–O bond scission and generates tertiary alkyl radicals
under Zn/MgCl2 conditions, wherein chelation of oxalates with
MgCl2 is crucial for activation of the oxalates.16 Such a
discovery prompted us to quest the feasibility of preparation
of tertiary alkyl boronates via the reaction of diboron with
tertiary alkyl oxalates under photo-induced conditions
(Scheme 1). Similar to Aggarwal’s borylation of carboxylic NP
esters (Scheme 1),13a the key in the C-O bond borylation is the
viability of addition of a boron radical to the carbonyl oxygen
of oxalates, which subsequently leads to a tertiary alkyl radical
via C-O bond fragmentation (Scheme 1). Addition of the
tertiary alkyl radical to diboron will ultimately give rise to the
alkylboronate products (Scheme 1).
During the course of preparation of the manuscript, Studer
reported a Ir-catalyzed photoredox borylation of tertiary alkyl
methyl oxalates.17 Therein an excited *IrIII intermediate was
proposed to serve as a strong reducing reagent that undergoes
single electron transfer to oxalate leading to homolytic
cleavage of C–O bond and affords tertiary alkyl radical, which
adds to diboron to give tertiary alkyl boronate. Herein, we
report that generation of boron radicals from B2cat2 under
transition metal free photoinduced conditions. Such a process
allowed us to develop a facile method for the preparation of
alkyl boronates via borylation of readily accessible tertiary
alkyl oxalates without a photoredox catalyst. The borylation
process can also be extended to the preparation of secondary
alkyl boronates using imidazole modified carbonthioates as the
C–O bond sources, although moderate efficiencies are
generally observed. We believe the present work
30
30
30
30
30
--
75%
91% (87%)d
0
1/3
1/3
Reaction Conditions: 450 nm LED, 1 (0.3 mmol), pinacol (3 equiv. based on
B2cat2), Et3N (1 mL), 24 h. a NMR yield using 2,5-Dimethylfuran as the internal
standard. b Room temp. c 48 h. d Isolated yield. e In dark, 55 oC.
To begin with, we set out to examine the coupling of 1 with
2.0 equiv of 2,2'-bibenzo[d][1,3,2]dioxaborole (B2cat2) under
blue light irradiation (power 0.5 W) in DMF for 24 h. We were
delighted to obtain the desired tertiary alkyl–Bpin product 2 in
16% yield (Table 1, entry 1) after quenching the unstable alkyl–
cat with pinacol.22 An extensive screening of the reaction
solvents and the power of the light bulb led us to identify that
DMF and 30 w of the light bulb were the optimal (entries 3–
10). With the increase of the stoichiometry of B2cat2 from 2 to
2.5 and to 3 equivalents, 2 was obtained in 51%, 67% and 75%
yields, respectively (entries 3, 11–12). By extending the
reaction time to 48 h, the yield for 2 was boosted to an
isolated 87% (entry 13). Thus, we chose the conditions in entry
13 that used 3 equiv of B2cat2 for further investigations.
The generality of the present borylation method was
evidenced for the preparation of a range of linear and ring-
containing tertiary alkyl–Bpin products (Figure 1). The tertiary
alkyl–Bpin 3–7a, 8–20 containing geminal dimethyl groups
were obtained in good to high yields. The functional group
compatibility proved to be broad; ester, F, Cl, CF3 and ether
were all tolerated. Replacement of a geminal methyl group in
7a by ethyl and n-butyl afforded 7b and 7c in 58% and 41%
yields, respectively, suggesting that increase of the sizes of the
tertiary alkyl groups may erode the borylation efficiency. This
notion was also supported by the formation of tertiary alkyl–
Bpin 13–18; the secondary alkyl moieties adjacent to the
boron-connected tertiary carbon centers seemingly resulted in
lower borylation yields than those of 8–11. The borylation
protocol was also applied to the oxalates derived from (+)-
estrone and lithocholic acid, affording the products 19 and 20
in synthetically useful yields. Access to the tertiary alkyl–Bpin
products featuring boron on 4-, 5-, 6-, 12-, and 15-membered
rings proved to be viable using the borylation protocol, as
evidenced by the examples of 21–29. The hetero oxygen and
sulfur atoms as in 26–27 were also compatible with the
reaction conditions. Finally, borylation of a benzylic tertiary
oxalates delivered an unexpected diboronate product 30 in a
complements the concurrent methods for the construction of
12, 13a, 17-18
sterically demanding tertiary alkyl boronates.6,
A
more careful study suggests the formation of a (DMF)2–B2cat2
adduct that absorbs light at 437 nm and gives Bcat radical to
initiate the radical addition process shown in Scheme 1.19
Finally, we discovered that the reaction of diboron with
alkenes effectively afforded alkyl diboronates under thermally
driven conditions without an exogenous additive.20-22
Table 1. Optimization for the formation of 2.
O
1.
B
O
2
h (450 nm LED) , DMF
Me
Bpin
O
Me
Me
Me
, 55 oC, 24 h
OMe
BzO
BzO
O
2. pinacol, Et3N
2
1
O
ratio of
1/B2cat2
Power
yielda
high yield. This result was inferred by in situ E-2 elimination of
the tertiary oxalates to give 2-methyl styrene followed by
diborylation.
Thus, we investigated the suitability of prop-1-en-2-
ylbenzene for the diborylation process under the standard
method. To our delight, 30 was obtained in 91% yield,
confirming that our speculation of in situ formation of alkenes
entry
solvent
(W)
0.5
0.5
30
30
30
1b
2 b
3
4
5
1/2
1/2
1/2
1/2
1/2
1/2
DMF
DMA
DMF
DMA
NMP
DMPU
16%
4%
51%
30%
43%
17%
6
30
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O
Me
View Article Online
Me
Me
BPin
Me
BPin
Et
Me
Me
Me
Me
BPin
Me
BPin
Me
Me
n-C9H19
DOI: 10.1039/D0CC04776G
Ph BPin
Me
BPin
O
Ph
Me
MeO
Me
a
3
4
5
6
7a
7b
: 58%
: 84%
: 71%
: 60%
: 52%(78% )
: 80%
OMe
Me
Cl
R
Me
Me
BPin
Ph
MeO
MeO
Me
BPin
Me
Me
Me
Me
Me
BPin
Me
BPin
: 41%
n-Pr
BPin
Ph
BPin
9a
, R = H: 83%
Ph
Cl
9b
9c
9d
9e
9f,
, R = Ph: 71%
, R = OBn: 75%
, R = F: 74%
, R = Cl: 66%
R = CF3: 82%
7c
8
10
11
12
: 60%
: 72%
: 74%
Me
: 52%
Me
Me
BPin
Me
BPin
Me
BPin
Me
Me
BPin
Ph
F
MeO
Me
Me
BPin
Me
BPin
Me
Me
O
Me
Me
Ph
Me
Me
13
14
15
16
17
18
: 30%
: 53%
: 45%
: 38%
: 43%
: 71%
Me
Me
Me
Me
BPin
O
Me
Me
BPin
Me
BPin
H
H
Me Me
H
H
Ph
BPin
: 87%
Me
Me
BPin
H
H
H
23
: 71%
21
22
: 63%
O
MeO
20
: 65%
19
58%
BPin
BPin
Me
BPin
Me
Me
BPin
Me
BPin
Me
Et
Me
BPin
BPin
: 46%
BPin
O
S
Ph
25
a
24
26
27
28
29
30
: 91%
: 39% (58% )
: 54%(dr = 4.4:1)
: 59%
: 43%
: 67%
Figure 1. The scope of tertiary alkyl methyl oxalates using the standard reaction conditions as in Table 1, entry 13, 450 nm LED, unactivated tertiary alkyl
methyl oxalates (0.3 mmol), B2cat2 (3 - 4.5 equiv.), DMF (1.2 mL), 55oC, 48 - 72h. a GC yield.
in the case of tertiary benzyl oxalate (vide supra, Figure 1).
Interestingly, the same reaction also proceeded without blue
carbothioate, which allowed transformation of secondary
alcohols to the corresponding boronates, as exemplified by
36–41 (Figure 3). The more sterically demanding substrates
were much less efficient as evidenced by the examples of 40–
41. The primary alcohols proved to be incompatible as verified
by the example of 42.
light, wherein 30 was obtained in 89% yield. In the previously
reported diborylation of alkenes with diboron, catalytic bases
were generally required.20-22 Thus, our diborylation method
can be viewed as a catalyst and base-free one. The scope of
alkenes for this diborylation approach proved to be broad. The
formation of secondary and tertiary boronates was
exemplified by 31–35. Functionalization of fattic acids
containing an internal alkene delivered 35 effectively. The
formation of cis-diboronates as in 33 and 34 suggest that
diborylation is a concerted process.21e
O
1.
B
O
2
h (450 nm LED) , DMF,
R1
N
R1
O
N
55oC, 32h
Bpin
R2
O
R2
S
2. pinacol, Et3N, 1h
B
1.
O
2
Bpin
Bpin
Me
Me
w/o h
DMF, 60 oC, 32 h
2. pinacol, Et3N
Bpin
Bpin
Bpin
Ph
Bpin
40%
36
37
38
39
: 38%
30
: 43%
Bpin
46%
: 89% yield
Bpin
Bpin
Bpin
Me
Me
Bpin
Bpin
Ph
Bpin Bpin
Bpin Ph
CO2Me
7
Me
7
Bpin
42
: trace
Ph
Me
Me
n
Bpin
35
a
33
34
, n =1: 96%
, n = 3, 90%
: 86%
40
: 12% (dr >20:1)
31
32
: 40%
: 95%
41
: 25%
a
Figure 3. Borylation of secondary alkyl imidazole-1-carbothioates.
Figure 2. Diborylation of alkenes under photo or thermal conditions. aonly
syn-addition product was observed.
To confirm that fragmentation of the C–O bond of tertiary
alkyl oxalates is a radical process, 43 was subjected to the
standard reaction conditions (Table 1, entry 13), which
provided the cyclization/borylation product 44 in a moderate
While No reaction occurred for secondary alkyl oxalates,23
the photo-induced catalyst-free borylation conditions were
also moderately effective for the imidazole-modified 1-
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ChemComm
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ARTICLE
Journal Name
yield (eq 1).23 This result is supportive of radical deoxgenation
of C–O bond. Subsequent C–B bond formation via radical
addition to B–B bond was proposed in a similar manner
suggested by Aggarwal (Scheme 1).23 Noteworthy is that the
cyclization involves conversion of a more stable tertiary alkyl
radical to a primary one, indicating that borylation of the latter
is kinetically more facile.
J. L. Stymiest, V. Bagutski, R. M. French and V. K. Aggarwal,
View Article Online
Nature, 2008, 456, 778.
5
(a) N. A. Owston and G. C. Fu, J. Am.DCOhIe: m10..1S0o39c./,D200C1C00,4717362G,
11908; (b) B. Saito and G. C. Fu, J. Am. Chem. Soc., 2007, 129,
9602.
A. S. Dudnik and G. C. Fu, J. Am. Chem. Soc., 2012, 134,
10693.
(a) C.-T. Yang, Z.-Q. Zhang, H. Tajuddin, C.-C. Wu, J. Liang, J.-
H. Liu, Y. Fu, M. Czyzewska, P. G. Steel, T. B. Marder and L.
Liu, Angew. Chem. Int. Ed., 2012, 51, 528; (b) H. Ito and K.
Kubota, Org. Lett., 2012, 14, 890.
S. K. Bose, K. Fucke, L. Liu, P. G. Steel and T. B. Marder,
Angew. Chem. Int. Ed., 2014, 53, 1799.
6
7
Me
Bpin
O
Me
Me
O
standard method
Me
OMe
O
(1)
8
9
O
O
43
44
51%
T. C. Atack, R. M. Lecker and S. P. Cook, J. Am. Chem. Soc.,
2014, 136, 9521.
10 T. C. Atack and S. P. Cook, J. Am. Chem. Soc., 2016, 138,
6139.
11 A. Joshi-Pangu, X. Ma, M. Diane, S. Iqbal, R. J. Kribs, R.
Huang, C.-Y. Wang and M. R. Biscoe, J. Org. Chem., 2012, 77,
6629.
12 C. Li, J. Wang, L. M. Barton, S. Yu, M. Tian, D. S. Peters, M.
Kumar, A. W. Yu, K. A. Johnson, A. K. Chatterjee, M. Yan and
P. S. Baran, Science, 2017, 356, eaam7355.
13 (a) A. Fawcett, J. Pradeilles, Y. Wang, T. Mutsuga, E. L. Myers
and V. K. Aggarwal, Science, 2017, 357, 283; (b) D. Hu, L.
Wang and P. Li, Org. Lett., 2017, 19, 2770; (c) J.-J. Zhang, X.
Duan, Y. Wu, J. Yang and L. Guo, Chem. Sci., 2019, 10, 161.
14 (a) J. Hu, G. Wang, S. Li and Z. Shi, Angew. Chem. Int. Ed.,
2018, 57, 15227; (b) J. Wu, L. He, A. Noble and V. K.
Aggarwal, J. Am. Chem. Soc., 2018, 140, 10700; (c) F.
Sandfort, F. Strieth-Kalthoff, F. J. R. Klauck, M. J. James and F.
Glorius, Chem.-Eur. J., 2018, 24, 17210.
Conclusions
In summary, we have developed an efficient C–B bond
forming method via borylation of unactivated tertiary alkyl
methyl oxalates that was induced by blue light. The reaction
did not require external photoredox metal cata-lysts, and
displayed excellent compatibility with a wide range of linear
and cyclic tertiary alcohol-derived oxalates. We believe this
work should add a new entry to the preparation of tertiary
alkyl boronates that are complementary to the concurrent
methods. Our catalyst-free borylation conditions (without light)
are suitable for diborylation of a wide range of alkenes
affording diboronates. The use of imidazole modified
carbonthioate allowed borylation of a number of secondary
alcohols in moderate efficiencies.
15 For a metal catalyst-free photo-induced borylation of organo
iodides: Y. Cheng, C. Mück-Lichtenfeld and A. Studer, Angew.
Chem. Int. Ed., 2018, 57, 16832.
16 Y. Yang, H. Chen, J. L. Sessler and H. Gong, J. Am. Chem. Soc.,
2019, 141, 820.
17 F. W. Friese and A. Studer, Angew. Chem., Int. Ed., 2019, 58,
9561.
Conflicts of interest
There are no conflicts to declare.
18 J. A. Myhill, L. Zhang, G. J. Lovinger and J. P. Morken, Angew.
Chem., Int. Ed., 2018, 57, 12799.
19 For a detailed discussion based on UV, 11B NMR and ESI
studies, see Figure S1-S13 in the Supplementary Information.
20 D. Shi, L. Wang, C. Xia and C. Liu, Angew. Chem. Int. Ed.,
2018, 57, 10318.
Acknowledgments
Financial support was provided by the Chinese NSF (Nos.
21871173). We thank Dr. Deli Sun for initial studies of the
secondary alcohols, and Prof. Jiarong Chen (Center China
Normal University) for use of UV-NIR spectrometer.
21 (a) F. Alonso, Y. Moglie, L. Pastor-Pérez and A. Sepálveda-
Escribano, ChemCatChem, 2014, 6, 857; (b) C. Pubill-
Ulldemolins, M. Poyatos, C. Bo, and E. Fernández, Dalton
Trans., 2013, 42, 746; (c) N. Miralles, J. Cid, A. B. Cuenca, J. J.
Carbó and E. Fernández, Chem. Commun., 2015, 51, 1693; (d)
A. Farre, K. Soares, R. A. Briggs, A. Balanta, D. M. Benoit and
A. Bonet, Chem.-Eur. J., 2016, 22, 17552; (e) A. Bonet, C.
Sole, H. Gulyás and E. Fernández, Org. Biomol. Chem., 2012,
10, 6621; (f) D. J. Blair, D. Tanini, J. M. Bateman, H. K. Scott,
E. L. Myers and V. K. Aggarwal, Chem. Sci., 2017, 8, 2898; (g)
J. Liu, M. Nie, Q. Zhou, S. Gao, W. Jiang, L. W. Chung, W.
Tang and K. Ding, Chem. Sci., 2017, 8, 5161; (h) X.-X. Wang, L.
Li, T.-J. Gong, B. Xiao, X. Lu and Y. Fu, Org. Lett., 2019, 21,
4298.
Notes and references
1
(a) P. Andrés, G. Ballano, M. I. Calaza and C. Cativiela, Chem.
Soc. Rev., 2016, 45, 2291; (b) R. Smoum, A. Rubinstein, V. M.
Dembitsky and M. Srebnik, Chem. Rev., 2012, 112, 4156. (c)
E. C. Neeve, S. J. Geier, I. A. I. Mkhalid, S.A. Westcott, and T.B.
Marder. Chem. Rev., 2016, 116, 9091-9161.
2
3
(a) G. A. Molander and N. Ellis, Acc. Chem. Res., 2007, 40,
275; (b) M. Norio, Bull. Chem. Soc. Jpn., 2008, 81, 1535-1553;
(c) J. A. Milligan, J. P. Phelan, S. O. Badir and G. A. Molander,
Angew. Chem. Int. Ed., 2019, 58, 6152.
(a) D. Leonori and V. K. Aggarwal, Acc. Chem. Res., 2014, 47,
3174; (b) B. S. L. Collins, C. M. Wilson, E. L. Myers and V. K.
Aggarwal, Angew. Chem. Int. Ed., 2017, 56, 11700; (c) I. A. I.
Mkhalid, J. H. Barnard, T. B. Marder, J. M. Murphy and J. F.
Hartwig, Chem. Rev., 2010, 110, 890.
22 (a) T. P. Blaisdell, T. C. Caya, L. Zhang, A. Sanz-Marco and J. P.
Morken, J. Am. Chem. Soc., 2014, 136, 9264; (b) L. Fang, L.
Yan, F. Haeffner and J. P. Morken, J. Am. Chem. Soc., 2016,
138, 2508.
23 See the Supporting Information for details.
24 For the discussion of the formation of B2Cat2-DMF complex,
see the SI. C. Kleeberg, A. G. Crawford, A. S. Batsanov, P.
Hodgkinson, D. C. Apperley, M. S. Cheung, Z. Lin, T. B. Marder, J.
Org. Chem., 2012, 77, 785-789.
4
(a) L. Zhang, G. J. Lovinger, E. K. Edelstein, A. A. Szymaniak,
M. P. Chierchia and J. P. Morken, Science, 2016, 351, 70; (b)
4 | J. Name., 2012, 00, 1-3
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DOI: 10.1039/D0CC04776G
Metal Catalyst-Free Photo-Induced Alkyl C–O Bond Borylation
Guobin Ma, Changzhou Chen, Sangita Talukdar, Xinluo Zhao, Chuanhu Lei* and Hegui Gong*
† College of Science, Center for Supramolecular Chemistry and Catalysis, Department of Chemistry and
Department of Physics, Shanghai University, 99 Shang-Da Road, Shanghai 200444, China
E-mail: chlei@shu.edu.cn and hegui_gong@shu.edu.cn
Tertiary alkyl boronates were prepared via C–O bond borylation of corresponding oxalates under
catalyst-free/(DMF)2–B2cat2 initiated visible light-induced conditions.
R2
R3
metal free
atomic economy
eco-friendly
R3
R1
O
Bpin
previliged scaffolds
36 examples
R2
R1
OMe
O
1. B2Cat2
Blue LED
O
up to 87% yield
2. pinacol
Et3N
R2
R2
S
R1
Bpin
wide FG tolerance
mild conditions
scalable
R1
O
N
N
6 examples
up to 46% yield