Enantioselective Reductive Coupling of Imines Templated by Chiral Diboron

Article abstract of DOI:10.1021/jacs.0c04558

We herein report a general, practical, and highly efficient method for asymmetric synthesis of a wide range of chiral vicinal diamines via reductive coupling of imines templated by chiral diboron. The protocol features high enantioselectivity and stereospecificity, mild reaction conditions, simple operating procedures, use of readily available starting materials, and a broad substrate scope. The method signifies the generality of diboron-enabled [3,3]-sigmatropic rearrangement.

Full text of DOI:10.1021/jacs.0c04558

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Communication
Enantioselective Reductive Coupling of Imines Templated by Chiral Diboron
Mingkang Zhou, Kaidi Li, Dongping Chen, Ronghua Xu, Guangqing Xu, and Wenjun Tang
J. Am. Chem. Soc., Just Accepted Manuscript • DOI: 10.1021/jacs.0c04558 • Publication Date (Web): 27 May 2020
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Enantioselective Reductive Coupling of Imines Templated by Chiral
Diboron
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Mingkang Zhou,† Kaidi Li,† Dongping Chen,† Ronghua Xu,† Guangqing Xu,* †, § and Wenjun Tang*,†,‡,§
†State Key Laboratory of Bio-Organic and Natural Products Chemistry, Center for Excellence in Molecular Synthesis,
Shanghai Institute of Organic Chemistry, University of Chinese Academy of Sciences, 345 Ling Ling Road, Shanghai
200032; ‡School of Chemistry and Material Sciences, Hangzhou Institute for Advanced Study, University of Chinese
Academy of Sciences, 1 Sub-lane Xiangshan, Hangzhou 310024, China. §NingBo Zejun Pharmaceutical Technology Co.,
Ltd, Hangzhou Bay New District, Ningbo 315336, China.
ABSTRACT:. We herein report a general, practical, and highly efficient method for asymmetric synthesis of a wide range of chiral
vicinal diamines via reductive coupling of imines templated by chiral diboron. The protocol features high enantioselectivity and
stereospecificity, mild reaction conditions, simple operating procedures, use of readily available starting materials, and a broad substrate
scope. The method signifies the generality of diboron-enabled [3,3]-sigmatropic rearrangement.
a. Preparation of racemic vicinal diamines
Chiral vicinal diamines are privileged substructures
ubiquitously found in active pharmaceutical ingredients,1 natural
"H-"
N
R
N
R
R
"N"
products,2 agrochemicals,3 as well as a number of ligands or
catalysts in the field of asymmetric catalysis.4 Their syntheses
have drawn considerable attention in organic chemistry. However,
most known methods (Figure 1a) including olefin diamination,5
nucleophilic addition of diimines,6 diimine reduction,7 and radical
coupling of imines only lead to racemic mixtures of vicinal
diamines,8 half of which are undesired waste. Moreover, the often
concomitant formation of the meso diastereomer with most
methods further compromises the yield of the desired product in
addition to the requirement of a tedious purification procedure.
Syntheses from chiral building blocks or auxiliaries provide
improved yields but require additional synthetic steps on the
expenses of valuable chiral starting materials (Figure. 1b).9,10 It
remains a significant challenge for efficient synthesis of chiral
vicinal diamines with excellent yields, selectivities, and
practicality. We herein report a general, simple, and practical
method for the synthesis of a wide range of chiral vicinal
diamines by developing a chiral diboron-templated reductive
coupling of imines. The protocol features excellent yields,
enantioselectivities and stereospecificities, mild reaction
conditions, simple operating procedures, use of readily available
starting materials,11 and a broad substrate scope.
(i)
(iii)
(iv)
reduction
diamination
R
N
NH HN
"R-"
N
"M"
N
R
R
(ii)
radical coupling
alkylation
R
b. Use of chiral substrates or auxilaries
H2N
NH2
O
HO
OH
HO
R
OH
R
steps
NH HN
R
H
R
R
c. Transition metal-free activation of diboron
ii) homolytic
ii) concerted
i) heterolytic
OMe-
Nu:
Nu:
B
B
N
N
N
N
B
B
B
B
B
B
OMe
B-
B
B
Nu
E+
d. Enantioselective reductive coupling templated by chiral diboron (this work)
Ar
Ar
Ph
O
O
O
O
B
B
Ar
Ar
(1 equiv)
R'
Diborons are often applied to carbon-boron bond-forming
reaction under action of a transition metal catalyst.12 They are also
able to react with electrophiles in the presence of a base under
transition metal-free conditions through heterolytic activation
(Figure. 1c),13,14 or generate radical species via
Ph
NH
R'
N
DB7
: Ar = 2,5-xyl
R
R
or
Ph
Ar
R
OH
OH
O
O
HN
R'
(cat)
B
B
R = Ar, alkyl
R' = H, Me
O
O
Ar
(1 equiv)
Figure. 1. Syntheses of vicinal diamines.
homolytic cleavage in the presence of nucleophiles.15,16
Activation of two reactants by a diboron species in a concerted
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fashion is rarely explored and will be particularly interesting and
prepared from the corresponding aldehydes, aliphatic aldimines 5
were prepared in situ from the corresponding nitriles 4 through
DIBAL-H reduction and applied directly with DB7 for the
reductive coupling.19 Besides chiral vicinal diamines 6a-c, 6n
with primary alkyl substituents, substituents with secondary alkyl
(6d-e), benzyl and substituted benzyl, thiophene-, alkene-, and
alkyne-incorporated alkyl were all compatible. The presence of
halogen, alkene, and alkyne functionalities were amenable for
further derivatization. Cyclic imines 7 were also applicable for
enantioselective reductive couplings.20 Thus, chiral 2,2'-
1
2
3
4
5
6
7
8
synthetically useful in forming a carbon-carbon bond with high
stereochemical fidelity. With the employment of a diboron
modified by a chiral diol, the chiral diboron can act as an
excellent reductive “template” for constructing a carbon-carbon
bond with high stereospecificity and enantioselectivity. We
previously reported a reductive coupling of isoquinolines in high
yields, excellent enantioselectivities, and stereospecificities by
employing a chiral diboron reagent, where a concerted diboron-
enabled [3,3]-sigmatropic rearrangement was discovered to form
a carbon-carbon bond with excellent stereochemical fidelity.17 We
envisioned that the chiral diboron-templated reductive couplings
would be applicable to various imine substrates and the
application of the concerted diboron-enabled [3,3]-sigmatropic
rearrangement can be expanded to a more general term.18 Herein
we report a general, practical, and highly efficient method for the
synthesis of a wide range of chiral vicinal diamines via reductive
coupling of various imines templated by chiral diboron (Figure.
1d).
bipyrrolidine
octahydrobiisoquinoline
(8a),
2,2'-bipiperidine
(8b),
and
1,1'-
5,5'-
9
(8c),
10
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12
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tetrahydrobidibenzo[c,e]azepine (8d) were formed in almost
perfect ee’s and good yields in a single step from corresponding
cyclic imines. N-Methyl aromatic aldimines 9 could also be
efficiently prepared from corresponding aldehyde 1. We were
pleased that such imines were suitable substrates for the diboron-
templated reductive coupling, for a range of N,N’-dimethyl 1,1’-
diaryl-substituted vicinal diamines in excellent ee’s and yields.
Such chiral building blocks required a lengthy synthetic sequence
otherwise, which were applied frequently as ligand in transition
Our proof-of-concept experiment started with reductive
coupling of phenylmethanimine 2a, which can be generated in
situ from benzaldehyde 1a and ammonia. A series of chiral
diboron DB1-7 were applied to the reaction using THF as the
solvent at room temperature (Figure. 2). Encouragingly, the
diboron DB1 derived from chiral pinanediol provided 3a in 80%
yield and 20% ee. Use of DB2 derived from (R)-1,1-
diphenylpropane-1,2-diol formed 3a in 70% yield and 36% ee.
51% ee was obtained when DB3 prepared from (1R,2R)-1,2-
diphenylethane-1,2-diol was employed. Interestingly, the diboron
DB4 derived from a non-C2-symmetric chiral diol was also
applicable, forming 3a in 57% ee. Use of a sterically bulkier
diboron DB5 provided an excellent yield (87%), but did not give a
better ee. Pleasingly, product 3a was formed in 80% ee when DB6
derived from a more hindered chiral diol, (R)-2-phenyl-1,1-di-o-
tolylethane-1,2-diol, was employed. Further optimization of the
diboron structure led to the development of DB7, which provided
an excellent yield (90%) and ee (95%).
metal-catalyzed cross-coupling reactions.21 Unfortunately,
a
bulkier N-alkyl aromatic aldimines such as N-ethyl benzaldimine
was inactive.
O
O
O
O
NH
NH2
O
B
B
*
*
NH3, THF, rt
H
H
THF, rt, 24 h, work-up
NH2
1a
2a
3a
Ph
Ph
Ph
Ph
O
O
O
O
O
O
B
O
O
O
O
Ph
B
B
B
B
B
Ph
Ph
O
O
Ph
DB1
DB2
DB3
80% yield, 20% ee
70% yield, 36% ee
75% yield, 51% ee
Ph
Ph
Ph
Ph
O
O
O
O
O
O
O
Ph
Ph
B
B
The chiral diboron DB7 proved to be highly effective for
reductive coupling of a wide range of aromatic aldimines.
Excellent ee’s and yields were achieved through the single-step
process for a series of 1,1’-diaryl-substituted vicinal diamines 3.
Various substituents either with electron-donating or withdrawing
properties regardless at para, ortho, meta position of the benzene
ring were all compatible. A number of functionalities such as
halogen, ester, alkoxy, alkynyl, and tertiary amine were well
tolerable. Heterocycles such as furan and thiophene as well as
naphthalene ring were applicable. It should be noted that no
formation of meso diamine side-product was observed in every
example listed in Figure 3, and most products were formed in
extremely high enantioselectivities (99% ee’s). A chiral steroid
skeleton was also compatible, while the chirality of the diamine
moiety in homocoupling product was dictated by the chirality of
the diboron, leading to a diastereomeric mixture of 3bb or 3cc
with either ~9:1 or ~1:9 ratio. Besides aromatic aldimines,
aliphatic aldimines could also be applied to the single-step
protocol to form a series of 1,1’-dialkyl-substituted vicinal
B
B
O
Ph
Ph
DB4
DB5
87% yield, 42% ee
80% yield, 57% ee
Ph
Ph
O
O
O
O
O
O
B
B
B
B
O
O
Ph
Ph
DB6
86% yield, 80% ee
DB7
90% yield, 95% ee
Figure. 2. Proof-of-concept experiment. Reactions were carried
out at rt in THF (2 mL) with 1a (0.5 mmol) and ammonia (15
equiv, 7.5 mmol, 7 M in MeOH) for 1 h followed by addition of
chiral diboron (0.5 equiv, 0.25 mmol). The mixture was further
stired at rt for 24 h. Isolated yields. The ee values were
determined by chiral HPLC analysis.
diamines
6
in satisfactory yields and almost perfect
enantioselectivities. Unlike aromatic aldimines which could be
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Journal of the American Chemical Society
NH
NH2
O
a.
Ar
DB7
( 1 equiv)
NH3, THF, rt
R2 NH2
1
2
H
H
Ar
Ar
Ar
THF, rt, 24 h, work-up
NH2
( 2 equiv)
1
2
3
R4
3
4
F
F
R1
F
NH2
NH2
NH2
NH2
R3
R4
R3
NH2 R2
: R2 = Cl, 92% yield, 99% ee
: R2 = Br, 90% yield, 99% ee
: R2 = Me, 89% yield, 85% ee
R4
5
6
NH2
NH2
F
NH2
3j
NH2
F
F
R1
R4
3k
3l
: R3 = Cl, 91% yield, 92% ee
: R3 = CF3, 82% yield, 99% ee
R
3 = EtO, 86% yield, 99% ee
3o
3p
7
: R4 = F, 90% yield, 99% ee
: R4 = Me, 90% yield, 99% ee
: R2 = OMe, 90% yield, 83% ee
3r
3m
3n
: R1 = F, 94% yield, 99% ee
3b
3c
8
: R2 = Ph, 75% yield, 91% ee
3q:
3s
3t
: 86% yield, 93% ee
: R1 = Cl, 90% yield, 99% ee
: R1 = Br, 96% yield, 99% ee
: R1 = Me, 96% yield, 99% ee
9
3d
3e
3f
S
NH2
S
NH2
NH2
O
O
NH2
10
11
12
13
14
15
16
17
18
19
20
21
22
23
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25
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53
54
55
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59
60
: R1 = MeO, 95% yield, 90% ee
: R1 = CF3O, 79% yield, 99% ee
: R1 = COOMe, 83% yield, 99% ee
3g
S
NH2
NH2
S
O
NH2
NH2
O
3h
3i
: R1 = CCH, 93% yield, 99% ee
3u
3v
3w
3x
: 90% yield, 96% ee
: 91% yield, 99% ee
: 89% yield, 96% ee
: 91% yield, 99% ee
O
Me
H
N
NH2
NH2
NH2
NH2
NH2
Bz
NH2
H
H
1
1'
H
H
Bz
NH2
N
NH2
H
Me
3bb
: 70% yield, 88:12 (RR:SS)
O
3y:
3z
3aa
3cc
DB7
)
90% yield, 99% ee
: 80% yield, 73% ee
: 90% yield, 96% ee
: 68% yield, 89:11 (SS:RR) (ent-
b.
NH2
NH
DIBAL-H, -78 o
MeOH
C
DB7
(1 equiv)
R
R
R
CN
R
THF, rt, 24 h, work up
H
NH2
(2 equiv)
4
5
6
NH2
NH2
NH2
NH2
NH2
NH2
NH2
NH2
: 54% yield, 99% ee
NH2 Br
NH2
NH2
6a
6b
6c
6d
6e
: 70% yield, 99% ee
: 53% yield, 99% ee
NH2
: 50% yield, 99% ee
: 40% yield, 99% ee
NH2
NH2
NH2
Cl
S
S
Cl
NH2
Br
6g
NH2
NH2
NH2
NH2
6i
: 85% yield, 99% ee
NH2
6f
6h
6j
: 76% yield, 99% ee
: 70% yield, 99% ee
NH2
: 70% yield, 99% ee
NH2
: 72% yield, 99% ee
NH2
NH2
NH2
NH2
NH2
6k
6l
6m
6n
: 65% yield, 99% ee
: 87% yield, 99% ee
: 85% yield, 99% ee
: 86% yield, 99% ee
H
c.
N
DB7
(1 equiv)
N
n
n
THF, rt, 24 h, work up
n
N
H
(2 equiv)
8
7
H
N
NH
NH
NH
HN
N
H
HN
8d
: 55% yield, 99% ee
HN
8a
8b
8c
: 68% yield, 98% ee
: 71% yield, 99% ee
: 80% yield, 99% ee
Me
d.
O
NMe
H
NH
Ar
CH3NH2 DCM
DB7 (1 equiv)
H
Ar
Ar
Ar
THF, 24 h, work up
HN
Me
(2 equiv)
1
9
10
Me
R5
Me
R6 NH
F
Me
NH
NH
Me
Me
R7
NH
NH
R7
HN
R6
F
HN
F
HN
Me
R5
Me
Me
HN
HN
: R6 = Cl, 88% yield, 97% ee
Me
Me
10j
: R1 = H, 92% yield, 98% ee
: R5 = F, 80% yield, 98% ee
: R5 = Cl, 85% yield, 98% ee
: R5 = Br, 95% yield, 99% ee
: R5 = Me, 85% yield, 97% ee
10k
10l
: R6 = Br, 84% yield, 95% ee
10n
10o
10p
: R7 = Cl,82% yield, 99% ee
: R7 = F, 90% yield, 98% ee
: R7 = EtO, 87% yield, 99% ee
10a
10b
10c
10d
10e
10f
F
: R6 = Me, 85% yield, 90% ee
: R6 = OMe, 88% yield, 99% ee
: 87% yield, 99% ee
Me
: 80% yield, 99% ee
Me
10m
10q
10r
Me
Me
Me
O
S
NH
NH
O
NH
NH
S
NH
: R5 = MeO, 85% yield, 99% ee
5
10g
10h
: R = CF3O, 77% yield, 96% ee
HN
O
HN
HN
S
HN
HN
O
S
5
Me
:65% yield,40% ee
Me
Me
: 88% yield, 99% ee
Me Me
10w
: 84% yield, 97% ee : 90% yield, 99% ee
: R = COOMe, 83% yield, 99% ee
5
10i
: R = CCH, 93% yield, 99% ee
10s
10t
10u
10v
: 85% yield, 97% ee
Figure. 3. Chiral diboron-templated enantioselective reductive coupling of imines. All yields are of isolated products. The ee values
were determined by chiral HPLC analysis. a. Reactions were carried out at rt in THF (1 mL) with 1 (0.2 mmol) and ammonia (15 equiv,
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3.0 mmol, 7 M in MeOH) for 1 h followed by addition of DB7 (0.1 mmol). The mixture was further stired at rt for 24 h. b. Reactions were
o
1
2
3
4
carried out in THF (1 mL) at -78 C with nitrile 4 (0.6 mmol) and DIBAL-H (0.6 mmol) for 3h, and then warmed to rt, followed by the
addition of DB7 (0. 3 mmol) and MeOH (0.66 mmol) at -78 oC. The mixture was further stirred at rt for 12 h. c.Reactions were carried out
at rt in THF (1 mL) with 7 (1.0 mmol) and DB7 (0.5 mmol) for 12 h. d. Imine 9 was prepared from 1 and MeNH2 in DCM. Reductive
couplings of 9 were carried out at rt in THF (1 mL) with 9 (0.5 mmol) and DB7 (0.25 mmol) for 12 h
5
6
7
8
The chiral diboron templated reductive coupling of imines
were not limited to the stoichiometric use of chiral diboron DB7.
For reductive coupling of stable aromatic imines 2 or 9, the
employment of a stoichiometric amount of (BNeop)2 (11) and a
catalytic amount of chiral diol 12 for the enantioselective
reductive coupling was equally effective (Figure. 4). Thus, by
employing bis(neopentyl glycolato)diboron as the nonchiral
diboron source and 30 mol % of chiral diol 12 as the catalyst, the
enantioselective reductive coupling of 9a proceeded
(168 g) and the mixture was stirred at rt for 24 h. Acidic/basic
work-up provided product 3a (40 g) as white solid in 80% isolated
yield and 95% ee, along with 90% recovery of chiral diol 12 (147
g). The method constituted one of most efficient protocols for the
synthesis of a wide array of chiral vicinal diamines.
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
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a. A scale-up experiment
OTMS
OMe
MgBr
THF, reflux
B2(OH)4
DB7
12
THF, reflux
O
Ph
OH
16
R'
BNeop
Ar'
N
(cat)
(99% ee)
62%
(99% ee)
99%
Ar
Ar
O
O
O
O
OH
12
NR'
B
B
+
Ar'
Ar'
N
Ar = 2,5-xylyl
BNeop
R'
11
: (BNeop)2
2
9
or
13
+
NH3
+
+
12
(7 M in MeOH)
(1.1 L)
1a
(50 g)
DB7
(168 g)
3a
(40 g)
12
(147 g)
OH
95% ee, 80% yield 90% diol recovery
OH
14
b.
Ar
Ar
R'
H
12
Ar'
N
N
B
Ar
O
B
O
O
N
Ph
Ph
Ar
Ar
Ph
2
9
or
H2O
Ar
O
B
DB7
[
]
O
O
B(OH)3
Ar'
O
B
R'
N
Ph
O
3a
15
H
Ar
Ar
NMe
11
12
(0.75 equiv)
(30 mol %)
1)
NHMe
Ar = 2,5-Me2Ph
A
H
THF, rt, 12 h
NHMe
Figure. 5. A scale-up experiment and stereochemical model
9a
2) MeOH
10a
88% yield, 96% ee
(1 equiv)
The high yields and enantioselectivities achieved on a variety
of chiral vicinal diamines and the fact that no meso products were
observed in any case further corroborated the generality of
diboron-enabled [3,3]-sigmatropic rearrangement process. The
successful protocol of employment of (BNeop)2 as the diboron
source and diol 12 as the catalyst further proved the importance of
the chiral diboron structure in promoting both reactivity and
enantioselectivity. It appeared that the sterically bulky and rigid
dioxaborolane of the diboron are crucial in providing an effective
six-membered ring transition state A (Figure. 5b), thereby
allowing the highly efficient reductive coupling to proceed. With
the compact and rigid diboron moiety with four 2,5-xylyl
substituents, the chirality on the diboron can be effectively
translated to the aldimine boron coordination, leading to excellent
stereocontrol. Interestingly, the ortho-methyl groups are in close
proximity to the aldimine coordination, manifesting their
importance in enhancing the enantioselectivity.
NHMe
NHMe
1) Zn/Me3SiCl
2) H2O
3) Li/isoprene
4) TA
9a
10a
NHMe
10a
NHMe
10a
(meso+rac)-
rac-
reference 33, 4 steps, 23% overall yield
Figure. 4. Asymmetric reductive coupling with a catalytic
amount of chiral diol
smoothly to form 10a, an effective chiral ligand for asymmetric
hydrogenation, in 88% yield and 96% ee. Besides a much simpler
operation procedure, the yield was significantly better than the
reported 23% yield using the zinc-mediated radical coupling-
lithium-mediated isomerization-resolution protocol.22 Noteworthy
was the dramatic acceleration effect by chiral diol 12. No
reductive coupling was observed when (BNeop)2 was mixed with
9a. The reaction proceeded to completion over 24 h when 12 was
added, indicating the significance of chiral diboron DB7 in
promoting both enantioselectivity and reactivity.
We anticipate that this simple, effective, and practical
synthetic methodology will significantly facilitate the chemistry of
chiral vicinal dimines as ligands and building blocks for
pharmaceutical and fine chemistry. From a view of basic science,
the enriched diboron-enabled [3,3]-sigmatropic rearrangement
from this study has provided a new addition to the repertoire of
valuable pericyclic reactions in organic chemistry, and the
discovery of new interesting reactions and applications is expected
by further exploiting this theory.
To test the scalability of the reaction, synthesis of 3a at a
decagram scale was pursued (Figure. 5a). Treatment of (R)-
mandelic acid derivative 16 with 2,5-xylyl Grignard reagent
formed chiral diol 12 in 62% yield. Reaction of 12 with
tetrahydroxydiboron in THF formed DB7 in almost quantitative
yield, which was prepared in a kilogram scale. To a solution of 1a
(50 g) dissolved in NH3/MeOH (7 M, 1.1 L) was charged DB7
4
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Journal of the American Chemical Society
ASSOCIATED CONTENT
Supporting Information
(DPPBA)-based
palladium-catalyzed
asymmetric
allylic
1
2
3
4
5
6
7
8
alkylation reactions:ꢀ A working model. Acc. Chem. Res. 2006, 39,
747. (f) Doyle, A. G.; Jacobsen, E. N. Small-molecule H-bond
donors in asymmetric catalysis. Chem. Rev. 2007, 107, 5713.
(5) (a) Chong, A. O.; Oshima, K.; Sharpless, K. B.
The Supporting Information is available free of charge on the
ACS Publications website at DOI:
Full experimental details and analytical data (PDF)
Synthesis
of
dioxobis(tert-alkylimido)osmium(VIII)
and
oxotris(tert-alkylimido)osmium(VIII) complexes. Stereospecific
vicinal diamination of olefins. J. Am. Chem. Soc. 1977, 99, 3420.
(b) Becker, P. N.; White, M. A.; Bergman, R. G. A new method
AUTHORINFORMATION
Corresponding Authors
for1,2-diamination
of
alkenes
using
cyclopenta-
Guangqing Xu Email: xugq@sioc.ac.cn
Wenjun Tang Email: tangwenjun@sioc.ac.cn
dienylnitrosylcobalt dimer/NO/LiAlH4. J. Am. Chem. Soc. 1980,
102, 5676. (c) Du, H.; Yuan, W.; Zhao, B.; Shi, Y. Catalytic
asymmetric diamination of conjugated dienes and triene. J. Am.
Chem. Soc. 2007, 129, 11688. (d) Fu, N.; Sauer, G. S.; Saha, A.;
Loo, A.; Lin, S. Metal-catalyzed electrochemical diazidation of
alkenes. Science. 2017, 357, 575. (e) Wu, M.; Fan, T.; Chen, S.;
Han, Z.; Gong L. Pd(II)-catalyzed asymmetric oxidative 1,2-
diamination of conjugated dienes with ureas. Org. Lett. 2018, 20,
2485. (f) Tao, Z.; Gilbert, B. B.; Denmark, S. E. Catalytic,
enantioselective syn-diamination of alkenes. J. Am. Chem. Soc.
2019, 141, 19161.
(6) (a) Roland, S.; Mangeney, P. A practical and efficient
synthesis of enantiomerically pure di-tert-butyl-ethanediamine.
Synthesis, 1999, 2, 228. (b) Alvaro, G. Grepioni, F.; Grilli, G.;
Maini, L.; Martelli, D.; Savoia, D. Asymmetric synthesis of 1,2-
diamines by the addition of allylic zinc and magnesium reagents
to N,N′-Bis[(S)-1-phenylethyl)]ethane-diimine. Synthesis, 2000,
4, 581. (c) Vemula, R., Wilde, N. C., Goreti, R., Corey, E. J. A
new, short, and stereocontrolled synthesis of C2-symmetric 1,2-
diamines. Org. Lett. 2017, 19, 3883.
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Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENT
The work is dedicated to the 70th anniversary of Shanghai Institute
of Organic Chemistry, Chinese Academy of Sciences. Financial
support is provided by the Strategic Priority Research Program of
the Chinese Academy of Sciences XDB20000000, CAS
(QYZDY-SSW-SLH029),
21572246, 21702223), STCSM-18520712200, and K.C. Wong
Education Foundation.
NSFC
(21725205,
21432007,
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TOC graphic
Ar
Ph
Ar
R'
O
B
O
B
Ar
Ar
NH
R'
Ph
N
O
R
O
R
R'
N
N R'
R
HN
R'
R
R
NHMe
NH2
NH2
n
n
Ar
Ar
R
N
N
R
Ar
Ar
H
H
NHMe
NH2
28 examples
up to 96% yield
up to 99% ee
NH2
14 examples
up to 88% yield
up to 99% ee
n = 1, 2, 3
4 examples
23 examples
up to 95% yield
up to 99% ee
up to 80% yield
up to 99% ee
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