Rhodium-Catalyzed Denitrogenative Transannulation of N-Sulfonyl-1,2,3-triazoles with Glycals Giving Pyrroline-Fused N-Glycosides

Article abstract of DOI:10.1021/acs.orglett.1c02141

Described here is a selective synthesis of 2,3-dihydropyrrole-fused N-glycosides through rhodium-catalyzed denitrogenative transannulation of N-sulfonyl-1,2,3-triazoles with glycals. A series of pyrroline-fused N-glycosides are afforded in moderate to exc

Full text of DOI:10.1021/acs.orglett.1c02141

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Letter
Rhodium-Catalyzed Denitrogenative Transannulation of N‑Sulfonyl-
1,2,3-triazoles with Glycals Giving Pyrroline-Fused N‑Glycosides
Jingjing Bi,* Qiang Tan, Hao Wu, Qingfeng Liu, and Guisheng Zhang*
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ABSTRACT: Described here is a selective synthesis of 2,3-
dihydropyrrole-fused N-glycosides through rhodium-catalyzed
denitrogenative transannulation of N-sulfonyl-1,2,3-triazoles with
glycals. A series of pyrroline-fused N-glycosides are afforded in
moderate to excellent yields with exclusive regioselectivity and
stereoselectivity. Functional application of such a resultant product
by oxidative addition and epoxidation is also explored. Notably, the
treatment of a pyrroline-fused N-glycoside (3a) with TMSOTf efficiently leads to an interesting unexpected C-nucleoside (9) via a
TMSOTf-inducing ring opening/acetyl migration/ring closing reaction sequence.
-Heterocyclic glycosides, widely present in many natural
Nproducts and bioactive compounds, make up a very
significant class of compounds.1 Nucleosides,2 glycoproteins,
and glycopeptides3 are the three important categories of N-
glycosides, which serve as clinical drugs and essential
components of DNA/RNA, enzymes, and antibodies in living
systems. With the development of glycobiology, more and
more structures containing pyrroline or N-glycosylated hetero-
cycles have been discovered, such as perinadine A,4
( )-aspidophylline A,5 and β-glucosidase inhibitor6 (Figure
1). They exhibit importantly physiological activities such as
antiviral, anticancer, antibacterial, and antifungal activities or
inhibition against several glycosidases.7
leukin inhibitory activity.5,10 As a consequence, various
methods have been developed to synthesize such structural
motifs.11 However, the synthesis of multisubstituted and chiral
DPPs has rarely been studied. Therefore, the development of
new methodologies for synthesizing N-glycosylated hetero-
cycles is desirable.
As special chiral DPPs analogues, 2,3-pyrroline-fused N-
glycosides (PFGs) containing two biologically important N-
glycoside and five-membered azaheterocycle12 motifs might
possess valuable biological activities (Scheme 1a). Further-
more, PFG compounds can be further modified through the
opening of the pyranose ring and hydrogenation,11a cyclo-
addition,13 dihydroxylation,14 or epoxidation15 of the double
bond in the pyrrole ring. However, to the best of our
knowledge, there has not been a general and concise method
for synthesizing structurally diverse PFGs. To date, a sole
synthetic method for the preparation of PFGs through six
reaction steps from glucal was reported by Rainier et al.
(Scheme 1b).16 Therefore, a direct and concise methodology
for the selective synthesis of structure-diverse PFGs will greatly
accelerate the development of new PFG functional molecules
and pharmaceuticals. In view of the versatile synthons of
glycals17 and N-sulfonyl-1,2,3-triazoles,18 we envisaged that the
direct denitrogenative transannulation of glycals with N-
sulfonyl-1,2,3-triazoles would provide a direct and reliable
method for constructing various PFGs (Scheme 1a). Herein,
we present an efficient and straightforward method for the
Figure 1. Biologically important DPPs and N-glycosylated hetero-
cycles.
Moreover, compared with O-glycosides, most N-glycosides
show stronger biological activities because they are less likely
to be hydrolyzed under physiological conditions.8 The
introduction of a sugar moiety through the N-glycosidic
bonds can significantly improve the activities of certain
biologically active natural products.9 Therefore, the efficient
and stereoselective synthesis of N-glycosides has attracted a
great deal of attention. Dihydropyrro[2,3-b]pyrans (DPPs)
have two distinct heterocycles of dihydropyrroles and pyrans,
which showed prominent antibacterial activities and inter-
Received: June 25, 2021
https://doi.org/10.1021/acs.orglett.1c02141
© XXXX American Chemical Society
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stereoselective preparation of PFGs through a Rh-catalyzed
denitrogenative transannulation of commercially available
glycals and N-sulfonyl-1,2,3-triazoles (Scheme 1c). Various
desired PFG compounds were obtained in moderate to
excellent yields, and high regioselectivity and stereoselectivity
via control of the substrate, instead of using chiral ligands.
Our initial investigation of the reaction condition was
conducted using the 4-phenyl-1-tosyl-1H-1,2,3-triazole (1a)
and commercially available 3,4,6-O-acetyl-D-glucal (2a) as the
model substrates (Tables S1−S5). After evaluating the catalytic
capacities of different Rh salts, we found that when the reaction
mixture was treated with 1.0 equiv of 1a and 1.2 equiv of 2a by
using Rh2(esp)2 (2 mol %) in 1,2-dichloroethane (DCE) at 80
°C for 0.5 h, the desired product 3a could be obtained in 44%
yield as a single diastereomer (Table S2). When Rh2(oct)4,
Rh2(OAc)4, Rh2(TFA)4, or Rh2(TPA)4 was used, 3a was
obtained in lower yields (entries 2−5, Table S1). The change
in temperature did not improve the efficiency of the reaction
(Table S2). By screening other solvents such as toluene, m-
xylene, C6H5Cl, and CH3CN, we found DCE was still the best
solvent for the process (entries 6−9, respectively, Table S1).
Meanwhile, we found that 1a was consumed rapidly and 3,4,6-
tri-O-acetyl-D-glucal (2a) was consumed slowly. Therefore, we
change the charging sequence for 2a and Rh2(esp)4 in DCE
Scheme 1. Synthesis of Pyrroline-Fused N-Glycosides
a−c
Scheme 2. Substrate Scope Evaluation for the Rh-Catalyzed Transannulation of 1,2,3-Triazoles with D-Glycal
a
Reaction conditions: 2a (0.2 mmol) and Rh2(esp)2 (0.004 mmol) dissolved in DCE (0.5 mL) at 80 °C, 1 (0.4 mmol) in DCE (3 mL) added
b
c
d
dropwise for 1 h, and reacted for an additional 0.5 h. Products formed in >20:1 dr as determined by the crude 1H NMR. Isolation yield. At 90
°C for 1 h. At 90 °C for 1.5 h. For 50 min. At 90 °C for 2 h.
e
f
g
B
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(0.5 mL) by adding 1a dropwise to the reaction mixture. To
our delight, the yield of 3a was increased to 51% (entry 10,
Table S1). To further explore the optimal conditions, different
1a:2a ratios from 1.2:1 to 4:1 in the presence of Rh2(esp)2 (2
mol %) were screened (entries 11−14, Table S1), and we
found that the desired product 3a was afforded in 85% yield
with a 1a:2a ratio of 2:1 (entry 14, Table S1). However,
changing the gas atmosphere to O2 or air furnished 3a in 64−
65% yield (Table S5). According to the screening of conditions
presented above, we determined that the reaction should be
conducted at 80 °C in DCE with the catalyst Rh2(esp)2 (2 mol
%). The structure of 3a was unambiguously determined by X-
ray crystallography.
In addition, D-galactals with Ac, Bz, and Bn protecting groups
were also good substrates for obtaining the desired PFGs (3i′,
88%; 3j′, 51%; 3k′, 55%). For L-rhamnal (3l′), the
cycloaddition could also successfully occur, and the structure
of 3l′ was unambiguously confirmed by X-ray crystallographic
analyses.
To demonstrate the potential of this chemistry, a gram scale
study was performed, and 3a was afforded in 51% yield
(Scheme 3a).
Scheme 3. Gram Scale Preparation and Synthetic
Applications of 3a
With the optimized reaction conditions in hand, we explored
the scope and generality of this methodology (Scheme 2).
Using 3,4,6-tri-O-acetyl-D-glucal (2a) as a model glycal, the
modified aryl groups of the triazoles (1) were first examined in
the Rh-catalyzed cycloaddition. Both electron-donating func-
tional groups (EDGs) and electron-withdrawing functional
groups (EWGs) on the benzene ring of 4-aryl-1-tosyl-1,2,3-
triazoles 1 with 2a could work well to form the desired
products 3a−3o in yields of 45−85%. The substituent position
and electronic effects obviously affected the reaction yields.
The products carrying EDGs (3b and 3l) and weak EWGs (3f,
3h, and 3j) were obtained in higher yields of 73−84%
compared to the moderate yields of those carrying strong
EWGs (3m and 3n). The products carrying the substituents at
the para position of the phenyl ring (3b, 3f, 3h, 3j, and 3l)
showed higher yields of 73−84% compared to the 61−67%
yields of those bearing the substituents at the meta position
(3c, 3e, 3g, 3i, and 3k). The substituent at the ortho position
of the phenyl ring (1d) afforded the product 3d in a much
lower yield of 45%. It was gratifying that the reaction of a
thienyl triazole (1o) also proceeded smoothly to produce the
desired 3o in a yield of 70%. However, when the substituent
was cyclohexyl, no desired product 3p was produced with the
consumption of triazole. A possible reason is that the stability
of cyclohexyl rhodium carbenoid was poor. Meanwhile, the
substituent was 1-naphthyl, the reaction also hardly occurred,
and a trace of product 3q was found.
At the same time, the N-sulfonyl groups of the triazole
substrates were also examined (3r−3z). When the substrates
with less reactive groups such as methanesulfonyl, isopropa-
nesulfonyl, and p-chlorobenzenesulfonyl groups were subjected
to the Rh-catalyzed cycloaddition, the desired products (3r−
3t) were produced in 61%, 57%, and 54% yields, respectively.
The reactions of N-phenylsulfonyl triazole (1u) and methyl-
and methoxyl-substituted phenylsulfonyl triazoles (1v−1x)
proceeded well in high yields of 70−80%. Unfortunately, we
did not obtain the desired product 3y when the phenyl ring
had a strong electron-withdrawing ester group. In addition,
when the aromatic ring is a naphthalene ring on the sulfonyl
group, the reaction hardly occurred.
Subsequently, diverse synthetic transformations from 3a
were carried out as illustrated in Scheme 3b−e. The
deprotection of 3a was attempted under alkaline conditions
with K2CO3 or NaOMe to afford 4 in 95% yield (Scheme 3b),
which constitutes the backbone of important biologically active
substances.7 Furthermore, oxidative addition of 3a with
mCPBA directly formed monoprotected diol 5 as a sole
stereoisomer in good yield,19 which was confirmed by HSQC,
HMBC NMR spectra, and a selective excitation experiment.
Then, the epoxidation of 3a with DMDO15 could yield 6 and
6′ in 90% yield with high diastereoselectivity (10/1 dr).
Next, we had a try to open the cyclic N,O-acetal moiety of 3
into polyhydroxy alkylpyrroles that possess potential biological
activities10,11 through an acid-catalyzed ring opening reaction.
When 10% TfOH,11 BF3·Et2O,20 or BCl3,21 was used in the
acid-catalyzed ring opening reactions, complex mixtures were
obtained, even at low temperatures. To our surprise, when 3a
was treated with TMSOTf,22 an unexpected product C-
nucleoside 7a was obtained in 67% yield instead of the ring
opening product polyhydroxy alkylpyrrole (Scheme 3e). The
structure of 7a was confirmed by mass spectra, HSQC, HMBC
NMR spectra, and a selective excitation experiment. Similarly,
7x can be obtained with a yield of 74% by treating 3x with
TMSOTf. C-Glycoside is an important structural unit with a
wide range of biological activities, such as cytotoxic and
antifungal activities.23 This unexpected transformation might
go by a three-step mechanism, including ring opening of the
epoxy, acetyl group migration,24 and nucleophilic substitution,
and provide a new alternative approach to such C-nucleosides
Finally, the scope of glycal substrates was examined. The Rh-
catalyzed cycloaddition of D-glycals containing various
protecting groups, such as methyl, benzyl (Bn), and benzoyl
(Bz), proceeded smoothly, forming the corresponding
products 3a′−3e′ in moderate to high yields (45−72%).
Notably, the allyl group could be tolerated, though the desired
N-glycoside 3f′ was afforded in 22% yield. The low yield of 3f′
might be attributed to the reactivity of the allyl group with
triazole. The glycal-containing Br or Ts groups were also able
to give the target products in high yields (3g′, 71%; 3h′, 80%).
C
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(Figure S1). Subsequently, the removal of the acetyl group of
C-nucleoside 7a under the alkaline condition gave compound
8 in quantitative yield.
On the basis of the observations presented above and
previous reports,11 a possible mechanism of the Rh-catalyzed
denitrogenative transannulation is depicted in Scheme 4. First,
AUTHOR INFORMATION
■
Corresponding Authors
Guisheng Zhang − Collaborative Innovation Center of Henan
Province for Green Manufacturing of Fine Chemicals, Key
Laboratory of Green Chemical Media and Reactions,
Ministry of Education, NMPA Key Laboratory for Research
and Evaluation of Innovative Drug, School of Chemistry and
Chemical Engineering, Henan Normal University, Xinxiang,
Henan 453007, China; orcid.org/0000-0001-9880-
950X; Email: zgs@htu.cn
Scheme 4. Proposed Mechanism
Jingjing Bi − Collaborative Innovation Center of Henan
Province for Green Manufacturing of Fine Chemicals, Key
Laboratory of Green Chemical Media and Reactions,
Ministry of Education, NMPA Key Laboratory for Research
and Evaluation of Innovative Drug, School of Chemistry and
Chemical Engineering, Henan Normal University, Xinxiang,
Henan 453007, China; Email: bijingjing@htu.cn
N-sulfonyl-1,2,3-triazole 1a provides α-diazoimine A by the
reversible ring-chain tautomerization. Then α-diazoimine A
interacts with rhodium(II) to yield α-imino rhodium(II)
carbenoid B through an irreversible process, along with the
release of nitrogen gas. The following electrophilic addition of
B to the double bond of glycal 2a produces cyclopropyl imine
C by neighboring group participation of 3-OAc.25 Then ring
opening of the cyclopropane occurred in the effect of the
electron-donating cycloalkoxy group to provide intermediate
D. Finally, the desired N-glycosides can be afforded by a
nucleophilic attack of the nitrogen atom of D by a cationic
oxocarbenium from the β face.25,26 In addition, the addition of
carbenoid B to the double bond of glycal 2a to afford the
desired N-glycoside by a [3+2] cycloaddition is another
pathway.
In summary, we have reported an efficient Rh-catalyzed N-
glycosylation approach for the stereoselective synthesis of
pyrroline-fused N-glycosides from commercially available
glycals and N-sulfonyl-1,2,3-triazoles. A mass of N-heterocyclic
glycosides could be afforded on the basis of the Rh-catalyzed
denitrogenative cycloaddition in good yields and exclusive
stereoselectivity without the use of chiral ligands or reagents.
Moreover, further functionalization of pyrroline-fused N-
glycosides by oxidative addition, epoxidation, and ring opening
also has been successfully applied. Further studies with respect
to the biological evaluations of pyrroline-fused N-glycosides
and the synthesis of complex N-heterocyclic glycosides using
our approach are ongoing in our laboratory and will be
reported in due course.
Authors
Qiang Tan − Collaborative Innovation Center of Henan
Province for Green Manufacturing of Fine Chemicals, Key
Laboratory of Green Chemical Media and Reactions,
Ministry of Education, NMPA Key Laboratory for Research
and Evaluation of Innovative Drug, School of Chemistry and
Chemical Engineering, Henan Normal University, Xinxiang,
Henan 453007, China
Hao Wu − Collaborative Innovation Center of Henan Province
for Green Manufacturing of Fine Chemicals, Key Laboratory
of Green Chemical Media and Reactions, Ministry of
Education, NMPA Key Laboratory for Research and
Evaluation of Innovative Drug, School of Chemistry and
Chemical Engineering, Henan Normal University, Xinxiang,
Henan 453007, China
Qingfeng Liu − Collaborative Innovation Center of Henan
Province for Green Manufacturing of Fine Chemicals, Key
Laboratory of Green Chemical Media and Reactions,
Ministry of Education, NMPA Key Laboratory for Research
and Evaluation of Innovative Drug, School of Chemistry and
Chemical Engineering, Henan Normal University, Xinxiang,
Henan 453007, China
Complete contact information is available at:
https://pubs.acs.org/10.1021/acs.orglett.1c02141
Notes
The authors declare no competing financial interest.
ASSOCIATED CONTENT
* Supporting Information
The Supporting Information is available free of charge at
https://pubs.acs.org/doi/10.1021/acs.orglett.1c02141.
ACKNOWLEDGMENTS
■
■
sı
This project was financially supported by the National Natural
Science Foundation of China (21877206, 21702051, and
U1604285), the Postdoctoral Science Foundation of Henan
Province (001802033), the Henan Science and Technology
Program (212102311022), and the Henan Key Laboratory of
Organic Functional Molecules and Drug Innovation.
Experimental details, characterization data of com-
pounds, NMR spectra, and X-ray crystallographic data
(PDF)
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REFERENCES
■
CCDC 1914996−1914997 contain the supplementary crys-
tallographic 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
Cambridge Crystallographic Data Centre, 12 Union Road,
Cambridge CB2 1EZ, UK; fax: +44 1223 336033.
(1) (a) Elshahawi, S. I.; Shaaban, K. A.; Kharel, M. K.; Thorson, J. S.
A Comprehensive Review of Glycosylated Bacterial Natural Products.
Chem. Soc. Rev. 2015, 44, 7591−7697. (b) Pałasz, A.; Ciez, D.;
̇
Trzewik, B.; Miszczak, K.; Tynor, G.; Bazan, B. In the Search of
Glycoside-based Molecules as Antidiabetic Agents. Top. Curr. Chem.
2019, 377, 19.
D
https://doi.org/10.1021/acs.orglett.1c02141
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pubs.acs.org/OrgLett
Letter
(2) Ramesh, D.; Vijayakumar, B. G.; Kannan, T. Advances in
Nucleoside and Nucleotide Analogues in Tackling Human
Immunodeficiency Virus and Hepatitis Virus Infections. ChemMed-
Chem 2021, 16, 1403−1419.
(19) Tiso, S.; Palombi, L.; Vignes, C.; Di Mola, A.; Massa, A.
Organocatalysts and Sequential Asymmetric Cascade Reactions in the
Synthesis of Functionalized Isoindolinones and Benzoindolizidinones.
RSC Adv. 2013, 3, 19380−19387.
(20) Ungureanu, I.; Bologa, C.; Chayer, S.; Mann, A. Phenylaziridine
as a 1,3-dipole. Application to the Synthesis of Functionalized
Pyrrolidines. Tetrahedron Lett. 1999, 40, 5315−5318.
(21) Ungureanu, I.; Klotz, P.; Schoenfelder, A.; Mann, A. The
Reactivity of N-Tosylphenylaziridine Versus N-Tosylphenylazetidine
in Heterocyclization Reactions. Tetrahedron Lett. 2001, 42, 6087−
6091.
(3) Balana, A. T.; Moon, S. P.; Pratt, M. R. O-GlcNAcylated
Peptides and Proteins for Structural and Functional Studies. Curr.
Opin. Struct. Biol. 2021, 68, 84−93.
(4) Saleem, M.; Ali, M. S.; Hussain, S.; Jabbar, A.; Ashraf, M.; Lee, Y.
S. Marine Natural Products of Fungal Origin. Nat. Prod. Rep. 2007,
24, 1142−1152.
(5) Subramaniam, G.; Hiraku, O.; Hayashi, M.; Koyano, T.;
Komiyama, K.; Kam, T.-S. Biologically Active Aspidofractinine,
Rhazinilam, Akuammiline, and Vincorine Alkaloids from Kopsia. J.
Nat. Prod. 2007, 70, 1783−1789.
(6) Doddi, V. R.; Kokatla, H. P.; Pal, A. P. J.; Basak, R. K.; Vankar, Y.
D. Synthesis of Hybrids of D-Glucose and D-Galactose with
Pyrrolidine-Based Iminosugars as Glycosidase Inhibitors. Eur. J. Org.
Chem. 2008, 2008, 5731−5739.
(7) Reddy, B. G.; Vankar, Y. D. The Synthesis of Hybrids of D-
galactose with 1-Deoxynojirimycin Analogues as Glycosidase
Inhibitors. Angew. Chem., Int. Ed. 2005, 44, 2001−2004.
(8) El-Khoury, R.; Damha, M. J. 2′-Fluoro-arabinonucleic Acid
(FANA): A Versatile Tool for Probing Biomolecular Interactions. Acc.
Chem. Res. 2021, 54, 2287−2297.
(9) Sangwan, R.; Khanam, A.; Mandal, P. K. An Overview on the
Chemical N-Functionalization of Sugars and Formation of N-
Glycosides. Eur. J. Org. Chem. 2020, 37, 5949−5977.
(10) (a) Kam, T. S.; Tan, S. J.; Ng, S. W.; Komiyama, K.
Bipleiophylline, an Unprecedented Cytotoxic Bisindole Alkaloid
Constituted from the Bridging of Two Indole Moieties by an
Aromatic Spacer Unit. Org. Lett. 2008, 10 (17), 3749−3752.
(11) (a) Kim, C.-E.; Park, Y.; Park, S.; Lee, P. H. Diastereoselective
Synthesis of Tetrahydrofurano- and Tetrahydropyrano-dihydropyr-
roles Containing N,O-Acetal Moieties via Rhodium-Catalyzed Trans-
annulation of N-Sulfonyl-1,2,3-triazoles with Oxacycloalkenes. Adv.
Synth. Catal. 2015, 357, 210−220. (b) Spangler, J. E.; Davies, H. M.
Catalytic Asymmetric Synthesis of Pyrroloindolines via a Rhodium-
(II)-Catalyzed Annulation of Indoles. J. Am. Chem. Soc. 2013, 135,
6802−6805.
(22) Rajasekar, S.; Anbarasan, P. Rhodium-Catalyzed Trans-
annulation of 1,2,3-Triazoles to Polysubstituted Pyrroles. J. Org.
Chem. 2014, 79, 8428−8434.
(23) Yang, Y.; Yu, B. Recent Advances in the Chemical Synthesis of
C-Glycosides. Chem. Rev. 2017, 117, 12281−12356.
(24) Lassfolk, R.; Rahkila, J.; Johansson, M. P.; Ekholm, F. S.;
̊
Wärna, J.; Leino, R. Acetyl Group Migration across the Saccharide
Units in Oligomannoside Model Compound. J. Am. Chem. Soc. 2019,
141, 1646−1654.
(25) Ma, X.; Tang, Q.; Ke, J.; Zhang, J.; Yang, X.; Shen, X.; Shao, H.
A Neighboring Group Participation Strategy: Direct and Highly
Diastereoselective Synthesis of 2-Substituted and 2,2-Bisubstituted
Perhydrofuro[2,3-b]pyran Derivatives. Org. Biomol. Chem. 2014, 12,
7381−7388.
(26) Whitfield, D. M.; Nukada, T. DFT Studies of the Role of C-2−
O-2 Bond Rotation in Neighboring-Group Glycosylation Reactions.
Carbohydr. Res. 2007, 342, 1291−1304.
(12) (a) Taylor, R. D.; MacCoss, M.; Lawson, A. D. G. Rings in
Drugs. J. Med. Chem. 2014, 57, 5845−5859. (b) Vitaku, E.; Smith, D.
T.; Njardarson, J. T. Analysis of the Structural Diversity, Substitution
Patterns, and Frequency of Nitrogen Heterocycles among U.S. FDA
Approved Pharmaceuticals. J. Med. Chem. 2014, 57, 10257−10274.
(13) Wei, S.; Yin, L.; Wang, S. R.; Tang, Y. Catalyst-Controlled
Chemoselective All-Alkene [2 + 2+2] and [2 + 2] Cyclizations of
Enamides with Electron-Deficient Alkenes. Org. Lett. 2019, 21, 1458−
1462.
(14) Zhang, Y. C.; Zhang, Z. J.; Fan, L. F.; Song, J. Enantioselective
Decarboxylative Propargylation/Hydroamination Enabled by Orga-
no/Metal Cooperative Catalysis. Org. Lett. 2018, 20, 2792−2795.
(15) Li, Y.; Tang, P. P.; Chen, Y. X.; Yu, B. Gold(I)-Catalyzed
Glycosidation of 1,2-Anhydrosugars. J. Org. Chem. 2008, 73, 4323−
4325.
(16) Jana, S.; Rainier, J. D. The Synthesis of Indoline and
Benzofuran Scaffolds Using a Suzuki-Miyaura Coupling/Oxidative
Cyclization Strategy. Org. Lett. 2013, 15, 4426−4429.
(17) (a) Kinfe, H. H. Versatility of Glycals in Synthetic Organic
Chemistry: Coupling Reactions, Diversity Oriented Synthesis and
Natural Product Synthesis. Org. Biomol. Chem. 2019, 17, 4153−4182.
(b) Yang, J.; Dai, Y.; Bartlett, R.; Zhang, Q. Convergent Palladium-
Catalyzed Stereospecific Arginine Glycosylation Using Glycals. Org.
Lett. 2021, 23, 4008−4012.
(18) For selected reviews, see: (a) Li, Y.; Yang, H.; Zhai, H. The
Expanding Utility of Rhodium-Iminocarbenes: Recent Advances in
the Synthesis of Natural Products and Related Scaffolds. Chem. - Eur.
J. 2018, 24, 12757−12766. (b) Davies, H. M. L.; Alford, J. S.
Reactions of Metallocarbenes Derived from N-Sulfonyl-1,2,3-triazoles.
Chem. Soc. Rev. 2014, 43, 5151−5162.
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