Construction of Chiral 1,3-Diamines through Rhodium-Catalyzed Asymmetric Arylation of Cyclic N-Sulfonyl Imines

Article abstract of DOI:10.1021/acs.orglett.9b01633

A rhodium/sulfur-olefin complex catalyzed asymmetric 1,2-addition of arylboronic acids to six-membered 1,2,6-thiadiazinane 1,1-dioxide-type cyclic imines to access highly optically active sulfamides (95-99% ee) has been developed. By taking advantage of t

Full text of DOI:10.1021/acs.orglett.9b01633

Letter
pubs.acs.org/OrgLett
Cite This: Org. Lett. XXXX, XXX, XXX−XXX
Construction of Chiral 1,3-Diamines through Rhodium-Catalyzed
Asymmetric Arylation of Cyclic N‑Sulfonyl Imines
Chun-Yan Wu† and Ming-Hua Xu*,†,‡
†State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, 555 Zu-chongzhi
Road, Shanghai 201203, China
‡Shenzhen Grubbs Institute and Department of Chemistry, Southern University of Science and Technology, 1088 Xueyuan
Boulevard, Shenzhen 518055, China
S
* Supporting Information
ABSTRACT: A rhodium/sulfur−olefin complex catalyzed
asymmetric 1,2-addition of arylboronic acids to six-membered
1,2,6-thiadiazinane 1,1-dioxide-type cyclic imines to access
highly optically active sulfamides (95−99% ee) has been
developed. By taking advantage of the simple functional group
transformations, an interesting array of valuable chiral 1,3-
diamines with different substitution patterns can be readily
obtained in a highly enantioenriched manner.
hiral 1,3-diamines are common motifs present in a large
number of organic molecules including natural products,1
transition-metal-catalyzed allylic amination and intramolecular
diastereoselective C−H amination offered new strategies for
the synthesis of optically active 1,3-diamines.9 However, most
of the available methods usually involve lengthy processes, thus
it still remains desirable to develop concise and highly
stereoselective approaches capable of accessing structurally
diverse and synthetically versatile chiral 1,3-diamines.
C
bioactive compounds,2 pharmaceutical agents,3 as well as chiral
ligands and catalysts4 (Figure 1). Due to this great importance,
Rhodium-catalyzed asymmetric addition of organoboron
reagents to imines has proved to be a powerful strategy for the
straightforward synthesis of diverse chiral amines. Recently,
numbers of cyclic imines were employed in rhodium-catalyzed
enantioselective addition of organoboron reagents, allowing for
access to a broad range of highly optically active cyclic amine
compounds containing multifunctional groups.10,11 Among
them, we have succeeded in efficient asymmetric addition to
1,2,5-thiadiazolidine 1,1-dioxide-type cyclic ketimines using a
simple chiral phosphite−olefin as a ligand.11f,k These methods
are useful for the synthesis of highly enantioenriched 1,2-
diamines through ring cleavage. In considering the con-
struction of a 1,3-diamine framework, we envisaged that the
incorporation of one more carbon in the heterocyclic system,
namely, employing 1,2,6-thiadiazinane 1,1-dioxide-type cyclic
imines as substrates for Rh-catalyzed asymmetric addition,
would be a potential protocol for accessing the 1,3-diamine
skeleton. Herein, we describe our successful development of
such an approach that could provide facile access to highly
enantioenriched diversely substituted chiral cyclic sulfamides
bearing 1,3-diamine scaffolds through the use of a simple
sulfur−olefin ligand (Scheme 1). After further synthetic
transformations, versatile acyclic and polycyclic chiral 1,3-
diamines were easily attained.
Figure 1. Examples of chiral 1,3-diamine-based bioactive compounds.
the construction of chiral 1,3-diamine scaffolds is known as an
important subject in organic synthesis. Accordingly, various
synthetic methods to access molecules containing a chiral 1,3-
diamine framework have been developed. Asymmetric
Mannich-type reaction using a certain type of nucleophiles
such as nitriles or enamides can lead to 1,3-dinitrogen-
containing products, but the generation of 1,3-diamines often
requires further reduction with hydride reagents.5 The
stereoselective ring-opening reaction of the substituted
aziridines with nucleophiles could also provide highly
enantioenriched 1,3-diamines efficiently.6 Additionally, chiral
1,3-diamines can be prepared by asymmetric conjugate
addition reaction7 and enantioselective 1,3-dipolar cyclo-
addition reaction8 followed by ring cleavage. Notably,
Received: May 8, 2019
© XXXX American Chemical Society
A
DOI: 10.1021/acs.orglett.9b01633
Org. Lett. XXXX, XXX, XXX−XXX

Organic Letters
Letter
a
Scheme 1. Addition Strategy to Chiral 1,3-Diamines
Table 1. Optimization of Reaction Conditions
b
c
d
entry
solvent
additive
yield (%)
ee (%)
1
2
3
4
5
6
7
8
toluene
toluene
toluene
toluene
toluene
toluene
dioxane
DCE
KF (1.0 equiv)
73
77
64
57
86
88
44
trace
82
78
73
99
98
99
99
99
99
98
-
K3PO4 (1.0 equiv)
KHF2 (1.0 equiv)
NEt3 (1.0 equiv)
KOH (1.0 equiv)
KOH (1.5 equiv)
KOH (1.5 equiv)
KOH (1.5 equiv)
KOH (1.5 equiv)
KOH (1.5 equiv)
KOH (1.5 equiv)
The six-membered 1,2,6-thiadiazinane 1,1-dioxide-type
cyclic imine substrates could be readily prepared by reaction
of sulfuric diamide with 1,1,3,3-tetramethoxypropane or 1,3-
dicarbonyl compounds through hydrogen chloride-promoted
dehydration.12 We began our work by evaluating the reaction
between 1a and p-methoxyphenylboronic acid 2a in KF (1.5
M)/toluene at 60 °C, in the presence of 2.5 mol % of
[Rh(COE)2Cl]2 and 5 mol % of various representative chiral
olefin ligands (L1−L5) that are prepared in our laboratory
(Scheme 2). Surprisingly, the use of the Rh/phosphite−olefin
e
9
10
11g
toluene
toluene
toluene
99
99
99
g
a
The reaction was carried out with 0.2 mmol of cyclic N-sulfonyl
aldimine 1a and 2.0 equiv of p-methoxyphenylboronic acid 2a in the
presence of 5 mol % of [Rh]/L3 with 2.0 mL of solvent at 60 °C for 8
h. Unless noted, 1.5 M solution was used. Isolated yield.
Determined by Chiral HPLC. The reaction was carried out in the
presence of 3 mol % of [Rh]/L3. With 1.5 equiv of p-
b
c
Scheme 2. Ligand Screening
d
e
f
g
methoxyphenylboronic acid 2a. With 1.2 equiv of p-methoxyphe-
nylboronic acid 2a.
observed when we tried to lower the catalyst loading to 3 mol
% (entry 9). When the reaction was carried out with the use of
less amount of arylboronic acid, a decrease of the yield was
observed while maintaining excellent enantioselectivity (entries
10 and 11).
With the optimal conditions in hand, we next investigated
the substrate scope of this asymmetric arylation (Scheme 3).
As revealed in Scheme 3, we were pleased to find that the Rh/
sulfur−olefin (L3) catalyst system could nicely apply to various
arylboronic acids with either electron-donating or -with-
drawing group(s) on the phenyl ring at different positions,
allowing the formation of the corresponding 3-aryl-substituted
sulfamide products with extremely high enantioselectivities
(98−99% ee, 3a−3l). Sterically bulky boronic acids can also
provide the desired 1,2-adducts smoothly (3l, 3m). Notably,
the reaction of heterocyclic boron reagents also proceeded
well. With 3-thienylboronic acid and 3-furanboronic acid, the
addition products were obtained with extremely high
enantioselectivity (98% ee) and medium yield (3o, 3p).
Moreover, substrates bearing various functional groups such as
halogen, vinyl, and phenyl at the 4-position were also suitable
for this catalytic system, providing the corresponding products
(3q−3t) in satisfactory yields with uniformly high enantiose-
lectivities. To further extend the substrate scope, we also
investigated the cyclic imines with other alkyl groups on the
nitrogen. To our delight, when substrates having N-methyl and
N-PMB groups were employed, the corresponding products
(3u, 3v) were obtained in 68% and 98% yields with no change
of the enantioselectivity (99% ee). It is noteworthy that the
reaction at 1 mmol scale with 1a and 2b proved also successful,
affording 3b in nearly quantitative yield with no notable loss of
enantioselectivity (95% yield, 99% ee).
(L1) catalyst system that works well for the previous five-
membered 1,2,5-thiadiazolidine 1,1-dioxide-type ketimines11k
could only deliver the desired product 3a in low yield (33%)
and poor enantioselectivity (47% ee). It was exciting to notice
that the branched sulfur−olefin ligand L3 exhibited excellent
catalytic reactivity and stereocontrol for 1,2-addition, giving
nearly optically pure cyclic sulfamide 3a with commendable
yield (73% yield, 99% ee). C1-symmetric chiral diene L4 also
displayed good reactivity and great enantioselectivity in the
reaction (60% yield, 97% ee). Other ligands including BINAP
can also produce the desired adduct, although the yields and
ee’s were inferior (L5, L6).
Encouraged by the promising result obtained with branched
chiral sulfur−olefin ligand L3, further investigations on
additives, solvents, and catalyst loading were carefully
conducted (Table 1). Among the various additives screened
(entries 1−5), KOH was found to be the best and gave the
highest yield (86%) with maintaining enantioselectivity (99%
ee) (entry 5). In the presence of 1.5 equiv of aqueous KOH
(1.5 M), the reaction afforded 3a in a slightly increased yield
(88%, entry 6). Solvent screening showed that toluene was the
best choice (entries 6−8). Slightly declined reaction yield was
To showcase the synthetic utility of this protocol, we next
carried out a series of experiments for product transformation
to construct structurally diverse chiral 1,3-diamines (Scheme
4). By taking advantage of the enamide functionality, allylation
B
DOI: 10.1021/acs.orglett.9b01633
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Organic Letters
Letter
Scheme 3. Rh-Catalyzed Asymmetric Addition of Cyclic N-
Sulfonyl Imines 1 with Arylboronic Acids
Scheme 4. Synthesis of Chiral 1,3-Diamines
a b c
, ,
a
The reaction was carried out with 0.2 mmol of cyclic imine 1, 2.0
equiv of arylboronic acid 2 in the presence of 5.0 mol % of [Rh]/L3,
and KOH (1.5 M, 1.5 equiv) in 2.0 mL of toluene at 60 °C for 2∼12
Figure 2. X-ray crystal structure of the cyclic sulfamide 4.
b
c
d
h. Isolated yield. Determined by Chiral HPLC. 4.0 equiv of
arylboronic acid was used.
6 under ring-opening conditions followed by the treatment
with MsCl/TEA led to a sequential cyclization to afford a
pyrrolidine-based chiral 1,3-diamine 7, which is otherwise
difficult to prepare. In the other case, triethylsilane reduction of
adduct 3b under trifluoroacetic acid conditions gave the cyclic
sulfamide product 8 without losing enantioselectivity. Accord-
ingly, a simple 1-substituted 1,3-diamine 9 could be attained
after ring cleavage. Derivatization of the sulfamide 8 to form a
polycyclic compound 10 has also been achieved by N-
acetylation and subsequent Friedel−Crafts reaction. In another
experiment, hydrogenation of 4-phenyl-substituted adduct 3r
over Pd/C in EA/ethanol at 40 °C was performed.
Interestingly, it was found that the reaction proceeded with
excellent diastereoselectivity (96% de) and gave syn-4,5-
substituted product 11 with high enantioselectivity (99% ee).
Removal of sulfonyl could then provide enantioenriched 1,2-
disubstituted 1,3-diamine 12. Thus, we were able to flexibly
construct an interesting array of 1-substituted, 1,2-disubsti-
of 3a with allyltrimethylsilane successfully proceeded in the
presence of TFA, furnishing the sole 3,5-anti-substituted 1,2,6-
thiadiazinane 1,1-dioxide 4 in excellent yield in a highly
enantiomerically enriched manner (99% ee).13 The structure
of 4 was confirmed by X-ray diffraction analysis, and the
absolute configurations of two carbon stereogenic centers were
determined to be (3R, 5S) (Figure 2). Assuming an analogous
addition mechanism, the same stereochemistry of the obtained
products 3 could be assigned. Ring cleavage of the cyclic
sulfamide 4 with trimethylenediamine under reflux condi-
tions,9b followed by the N-Boc-protection, could lead to acyclic
chiral 1,3-disubstituted 1,3-diamine 5 bearing useful allyl and
aryl functional groups without any loss of enantiopurity (99%
ee). On the other hand, hydroboration of the terminal alkenyl
of cyclic sulfamide 4 gave alcohol intermediate 6. Exposure of
C
DOI: 10.1021/acs.orglett.9b01633
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Organic Letters
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be useful in organic synthesis and medicinal chemistry.
To summarize, we have developed a highly effective
rhodium/sulfur−olefin ligand catalytic system for asymmetric
addition of arylboronic acids to six-membered 1,2,6-thiadiazi-
nane 1,1-dioxide-type cyclic imines bearing an enamide moiety.
The reaction facilitates the preparation of diverse cyclic
sulfamides in high yields with excellent enantioselectivities
(95−99% ee) under mild conditions. More importantly, a
series of valuable chiral 1,3-diamines with different substitution
patterns can be readily obtained in a highly enantioenriched
manner by simple conversions. Given the great importance of
chiral 1,3-diamines, we believe that this protocol would find
applications in related drug discovery studies and asymmetric
organic synthesis.
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ASSOCIATED CONTENT
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Experimental procedures and spectroscopic data of all
new compounds (PDF)
Accession Codes
CCDC 1914877 contains the supplementary crystallographic
data for this paper. These data can be obtained free of charge
via www.ccdc.cam.ac.uk/data_request/cif, or by emailing
data_request@ccdc.cam.ac.uk, or by contacting The Cam-
bridge Crystallographic Data Centre, 12 Union Road,
Cambridge CB2 1EZ, UK; fax: +44 1223 336033.
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AUTHOR INFORMATION
Corresponding Author
■
*E-mail: xumh@simm.ac.cn or xumh@sustech.edu.cn.
2007, 9, 1553. (c) Rueping, M.; Maji, M. S.; Kucu̧ k, H. B.; Atodiresei,
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(e) Pradipta, A. R.; Tanaka, K. Bull. Chem. Soc. Jpn. 2016, 89, 337.
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(c) Liu, Y.; Xie, Y.-J.; Wang, H.-L.; Huang, H.-M. J. Am. Chem. Soc.
2016, 138, 4314.
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Chem. Soc. 2012, 134, 5056. (b) Luo, Y.-F.; Carnell, A. J.; Lam, H. W.
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ORCID
Ming-Hua Xu: 0000-0002-1692-2718
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
We thank the National Science & Technology Major Project
“Key New Drug Creation and Manufacturing Program”, China
(2018ZX09711002-006), and the National Natural Science
Foundation of China (81521005, 21472205, 21325209) for
financial support.
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