Bamford-Stevens reaction assisted synthesis of styrene C-glycosides

Article abstract of DOI:10.1080/00397911.2019.1606921

Modification of carbohydrates and their analogs is hindered due to multi-step synthetic methodologies involving selective protection and deprotection of multiple hydroxyl groups present in the molecule. A highly efficient route for the synthesis of 1-phen

Full text of DOI:10.1080/00397911.2019.1606921

Synthetic Communications
An International Journal for Rapid Communication of Synthetic Organic
Chemistry
ISSN: 0039-7911 (Print) 1532-2432 (Online) Journal homepage: https://www.tandfonline.com/loi/lsyc20
Bamford-Stevens reaction assisted synthesis of
styrene C-glycosides
Balram Singh, Sandeep Kumar, Jyotirmoy Maity, Indrajit Roy & Ashok K.
Prasad
To cite this article: Balram Singh, Sandeep Kumar, Jyotirmoy Maity, Indrajit Roy & Ashok K.
Prasad (2019): Bamford-Stevens reaction assisted synthesis of styrene C-glycosides, Synthetic
Communications, DOI: 10.1080/00397911.2019.1606921
To link to this article: https://doi.org/10.1080/00397911.2019.1606921
View supplementary material
Published online: 07 May 2019.
Submit your article to this journal
View Crossmark data
Full Terms & Conditions of access and use can be found at
https://www.tandfonline.com/action/journalInformation?journalCode=lsyc20

R
SYNTHETIC COMMUNICATIONSV
https://doi.org/10.1080/00397911.2019.1606921
Bamford-Stevens reaction assisted synthesis of styrene
C-glycosides
Balram Singh, Sandeep Kumar, Jyotirmoy Maity, Indrajit Roy, and Ashok K. Prasad
Bioorganic Laboratory, Department of Chemistry, University of Delhi, Delhi, India
ABSTRACT
ARTICLE HISTORY
Received 27 February 2019
Modification of carbohydrates and their analogs is hindered due to
multi-step synthetic methodologies involving selective protection
and deprotection of multiple hydroxyl groups present in the mol-
ecule. A highly efficient route for the synthesis of 1-phenyl-2-(b-D-
glycopyranosyl)ethenes has been developed from native sugars,
which neither requires protection/deprotection of the hydroxyl
groups nor use of any metal/metal ions. The key step of the devel-
oped methodology is the use of Bamford-Stevens reaction which led
to the formation of the desired compounds in moderate to high
yields in three steps only.
KEYWORDS
Bamford-Stevens reaction;
carbohydrates;
Glycopyranosyl ethenes;
styrene C-glycoside
GRAPHICAL ABSTRACT
Introduction
C-Glycosides are a family of stable carbohydrate derivatives that have drawn the atten-
tion of chemists due to their interesting biological properties.[1–3] They are also used as
precursors for the synthesis of C-glycoside mimics of glycolipids,[4] oligosaccharides,[5]
glycoproteins,[6] and other natural and biologically active compounds.[7,8] The conform-
ation of the native sugars and their C-glycosides have very little difference[9] but the
pharmacological profile of C-glycosides vary significantly from its native O-glycosides as
the glycosidic C–C bond is not cleavable under normal physiological conditions making
them ideal surrogates of native O-glycosides as therapeutic agents.[10–13] In spite of vari-
ous utility and natural origin of many C-glycosides,[14] their availability is often hedged
by the report of complicated synthesis from corresponding native sugars.
The aim of this study is to develop an efficient metal free synthetic methodology for
the preparation of styrene C-glycosides, which is a key intermediate molecule en-route
to various natural and biologically active carbohydrate derivatives.[15–21] The synthesis
of styrene C-glycosides reported earlier has been smeared either by inclusion of
protection/deprotection steps, use of toxic transition metals or by formation of mixture
CONTACT Ashok K. Prasad
ashokenzyme@gmail.com; Indrajit Roy
indrajitroy11@gmail.com
Bioorganic
Laboratory, Department of Chemistry, University of Delhi, Delhi, 110 007, India.
Supplemental data for this article can be accessed the publisher’s website.
ß 2019 Taylor & Francis Group, LLC

2
B. SINGH ET AL.
[22]
of a- and b-anomers or E-Z isomers.[22–29] Recently, Kaszas et al.,
have reported the
ꢀ
synthesis of styrene C-glycoside by Pd-catalyzed cross coupling reaction of anhydro-
aldose tosylhydrazone with benzyl bromides in moderate yields. However, one of the
drawbacks of the reaction is the formation of mixture of compounds and the other is
the multistep synthesis of starting aldehyde, i.e. anhydro-aldoses from native sugars that
require protection/deprotection of multiple sugar hydroxyl groups too. Herein, we
report the synthesis of (E)-1-phenyl-2-(b-D-glycopyranosyl)ethenes in 54–84% overall
yields in three steps starting from unprotected hexose sugars. The developed method-
ology is convenient and efficient compared to the literature procedures where either
transition metals or protection/deprotection chemistry has been used often leading to
the formation of mixture of isomeric products. We have used Bamford-Stevens reac-
tion,[30] which have recently attracted much interest in organic synthesis, in one of the
crucial steps for the synthesis of 1-phenyl-2-(b-D-glycopyranosyl)ethenes.[31,32]
Results and discussion
Three hexoses, i.e. D-glucose (1a), D-galactose (1b), and D-mannose (1c) were select-
ively converted to b-C-glycosyl benzoylmethane (2a, 2b, and 2c, respectively) on treat-
ment with 1,3-diphenylpropan-1,3-dione (dibenzoylmethane) in the presence of sodium
bicarbonate (NaHCO3) at 90 ꢀC in ethanol:water mixture (4:1), in quantitative yields,
except in case of D-galactose (71% yield).[25,33] The b-configuration of benzoyl methyl
group in compounds 2a-c has been proved by NOE spectroscopy, which has also been
supported by literature reports.[25,33] The refluxing of compounds 2a-c with p-toluene-
sulphonyl hydrazide in the presence of catalytic amount of glacial acetic acid at 70 ꢀC in
methanol afforded 1-phenyl-2-(b-D-glycopyranosyl)ethylidene p-toluoylsulfonyl hydra-
zide (3a-c) in 87–94% yields. It was envisaged that Bamford–Stevens reaction can be
used for the synthesis (E)-1-phenyl-2-(b-D-glycopyranosyl)ethenes (4a-c) from the cor-
responding hydrazides 3a-c via the formation of diazo-intermediate followed by gener-
ation of carbocation and in turn the formation of the desired products in basic
condition (Scheme 1).
The Bamford-Stevens reaction condition with respect to the use of base and solvent
for the efficient synthesis of (E)-1-phenyl-2-(b-D-glycopyranosyl)ethenes (4a-c) was
optimized by the conversion of 1-phenyl-2-(b-D-galactopyranosyl)ethylidene
Scheme 1. Bamford–Stevens reaction assisted synthesis of styrene C-glycosides 4a-c.

R
SYNTHETIC COMMUNICATIONSV
3
Table 1. Optimization of Bamford–Stevens reaction condition for the conversion of hydrazide 3b to
styrene C-glycoside 4b.
Entry
Base
Solvent
Additive
T (oC)
Time (h)
Yield (%)
1.
2.
3.
4.
5.
6.
7.
8.
Et3N
DBU
KOH
KOH
KOH
K2CO3
K2CO3
NaOMe
NaOMe
NaOMe
MeLi
MeLi
nBuLi
nBuLi
DMF
DMF
–
–
–
H2O
H2O
–
H2O
–
H2O
H2O
–
–
–
110
110
110
70
110
110
110
110
70
30
30
12
16
24
16
16
16
16
16
3
nra
nra
9
20
20
5
10
20
30
89
nrb
nrb
nrb
nrb
1,4-Dioxane
MeOH
MeOH
1,4-Dioxane
MeOH
1,4-Dioxane
MeOH
MeOH
THF
9.
10.
11.
12.
13.
14.
110
ꢁ40
0
THF
THF
THF
3
3
3
ꢁ40
–
0
Reaction conditions unless otherwise specified: base (10 equiv.); additive ¼ 0.1 equiv.; nra ¼ no reaction; nrb ¼ insepar-
able mixture.
p-toluoylsulfonyl hydrazide (3b) to (E)-1-phenyl-2-(b-D-galactopyranosyl)ethene (4b) as
a model reaction in sealed reaction vessel (Table 1). It was observed that the use of
organic bases, such as triethylamine (Et3N) and 1,8-diazabicyclo[5.4.0]undec-7-ene
(DBU) in DMF failed to initiate the conversion of hydrazide 3b into alkene 4b even
after a prolonged heating at 110 ꢀC (Table 1, entries 1–2). However, application of inor-
ganic bases, such as potassium hydroxide (KOH) and potassium carbonate (K2CO3)
either in 1,4-dioxane or in aqueous methanol initiated the formation of alkene from
hydrazide, but to a very less extent which is of no practical utility (Table 1, entries
3–7). Likewise, the use of sodium methoxide (NaOMe) in dioxane at 110 ꢀC and in
aqueous methanol at 70 ꢀC did not lead to an appreciable improvement in the yield of
C-styryl galactoside. However, employment of NaOMe in aqueous methanol at 110 ꢀC
led to the conversion of hydrazide to (E)-1-phenyl-2-(b-D-galactopyranosyl)ethenes (4b)
in 89% yield (Table 1, entries 8–10). The application of optimized Bamford-Stevens
reaction condition on 1-phenyl-2-(b-D-glucopyranosyl)ethylidene p-toluoylsulfonyl
hydrazide (3a) and 1-phenyl-2-(b-D-mannopyranosyl)ethylidene p-toluoylsulfonyl
hydrazide (3c) led to the formation of (E)-1-phenyl-2-(b-D-glucopyranosyl)ethene (4a)
and (E)-1-phenyl-2-(b-D-mannopyranosyl)ethenes (4c) in 89 and 84% yields, respect-
ively. The trans geometry of the double bond, i.e. exclusive formation of (E)-1-phenyl-
2-(b-D-glycopyranosyl)ethenes (4a-c) was revealed by the coupling constant of two dou-
ble bond protons (J ¼ 16.0 Hz).
There is an alternative approach to generate diazo intermediate from suitable hydra-
zides, such as 1-phenyl-2-(b-D-galactopyranosyl)ethylidene p-toluoylsulfonyl hydrazide
(3b) utilizing organolithium compounds which in turn can be converted into styrene C-
galactoside as per Shapiro reaction.[34] Thus, hydrazide 3b in dry THF was treated with
methyl lithium/n-butyl lithium at -40 ꢀC and also at 0 ꢀC, but the reaction did not yield
the desired product. This might happen because of the presence of free hydroxyl groups
on sugar moiety of hydrazides (Table 1, entries 11–14).
The structures of all the synthesized compounds 2a-c, 3a-c, and 4a-c were unambigu-
1
ously established on the basis of their spectral (IR, H & 13C NMR and HRMS) data

4
B. SINGH ET AL.
analysis (See Supplementary Material). The structures of known compounds 2a-c were
confirmed on the basis of comparison of their spectral data with those reported in the
literature.[25,33]
Conclusion
We have developed a simple, efficient and eco-friendly route for exclusive synthesis of
(E)-1-phenyl-2-(b-D-glycopyranosyl)ethenes from native sugars using Bamford-Stevens
reaction in one of the crucial steps. The developed methodology does not require any
protection/deprotection step(s) or metal ion-catalysis and is selective to afford the trans
product only.
Experimental
All reactions were performed under normal atmospheric conditions. Commercial chem-
icals, reagents and solvents were purchased from local commercial sources and used
without any further purification. Rf values are reported for analytical TLC using the
specified solvents and 0.25 mm silica gel 60F254 plates that were visualized by UV irradi-
ation or by charring with 5% alcoholic sulfuric acid solution (5% conc. H2SO4 in
EtOH). Solvents were removed under reduced pressure using rotary evaporator, fol-
lowed by further drying of the residual solvents under high vacuum. Column chroma-
tography was performed on silica gel (100–200 mesh). The IR spectra were recorded on
a Perkin-Elmer model 2000 FT-IR spectrometer by making KBr disk for solid samples
1
and neat for liquid samples. The H- and 13C-NMR spectra were recorded on Jeol Delta
400 MHz and 100.6 MHz spectrometer, respectively using tetramethylsilane (TMS) as
internal standard. The chemical shift values are on d scale and the coupling constant (J)
1
are in Hz. H NMR spectra in CD3OD were referenced at d ¼ 3.31 ppm. The 13C NMR
spectra in CD3OD were referenced at d ¼ 49.00 ppm. The following abbreviations were
used to designate signal multiplicity, s ¼ singlet, d ¼ doublet, t ¼ triplet, m ¼ multiplet.
HRMS analysis was carried out using Agilent G6530AA LC Q-TOF mass spectrometer
using ESI method. The optical rotation was measured on a Rudolph Autopol II auto-
matic polarimeter using 589 nm wavelength’s light.
Synthesis of 1-phenyl-2-(b-D-glucopyranosyl)ethylidene p-toluoylsulfonyl
hydrazide (3a)
Compound 2a (500 mg, 1.77 mmol) was taken in two necked round bottom flask and
dissolved in methanol (5 mL) followed by addition of glacial acetic acid (10 mg,
0.17 mmol). The reaction was refluxed for 15 min at 70 ꢀC before the stepwise addition
of p-toluenesulphonyl hydrazide (363 mg, 1.9 mmol) dissolved in methanol (5 mL). The
reaction was stirred under refluxing condition for 12 h. After complete disappearance of
the starting material on TLC, reaction mixture was concentrated under reduced pressure
and purified by column chromatography using 7% methanol in DCM as eluent to give
hydrazide 3a, which was obtained as colorless oil (755 mg) in 94% yield; IR (KBr, ꢀmax
/
1
cmꢁ1): 3352, 2918, 2850, 1598, 1072; H NMR (400 MHz, CD3OD): d 2.42 (s, 3H),

R
SYNTHETIC COMMUNICATIONSV
5
2.88–3.0 (m, 3H), 3.12–3.19 (dd, 1 H, J ¼ 14.2, 8.5 Hz), 3.45–3.62 (m, 5H), 7.29–7.34 (m,
3H), 7.39 (d, 2 H, J ¼ 8.0 Hz), 7.59–7.65 (m, 2H), 7.90 (d, 2 H, J ¼ 8.0 Hz).; 13C NMR
(100.6 MHz, CD3OD) d 20.24, 29.43, 60.91, 66.40, 71.08, 74.59, 75.66, 80.40, 126.23,
127.94, 128.19, 129.29, 129.41, 135.96, 136.40, 144.10, 153.20; HRMS (ESI) m/
z ¼ 451.1533 (calculated for C21H27N2O7S [M þ H]þ ¼ 451.1539).
Acknowledgments
BS and SK thank CSIR, New Delhi for award of Junior/Senior Research Fellowships. We are
grateful to CIF-USIC, University of Delhi for providing the NMR spectral and HRMS record-
ing facilities.
Funding
The authors thank University of Delhi for providing financial support under DU-DST Purse
Grant for the execution of the work.
References
[1] Pal, K. B.; Mahanti, M.; Huang, X.; Persson, S.; Sundin, A. P.; Zetterberg, F. R.; Oredsson,
S.; Leffler, H.; Nilsson, U. J. Quinoline-Galactose Hybrids Bind Selectively with High
Affinity to a Galectin-8 N-Terminal Domain. Org. Biomol. Chem. 2018, 16, 6295–6305.
DOI: 10.1039/c8ob01354c.
[2] Xiao, J.; Capanoglu, E.; Jassbi, A. R.; Miron, A. Advance on the Flavonoid C-Glycosides
and Health Benefits. Crit. Rev. Food Sci. Nutr. 2016, 56, S29–S45. DOI: 10.1080/
10408398.2015.1067595.
[3] de Winter, T. M.; Balland, Y.; Neski, A. E.; Petitjean, L.; Erythropel, H. C.; Moreau, M.;
Hitce, J.; Coish, P.; Zimmerman, J. B.; Anastas, P. T. Exploration of a Novel, Enamine-
Solid-Base Catalyzed Aldol Condensation with C-Glycosidic Pyranoses and Furanoses.
ACS Sustainable Chem. Eng. 2018, 6, 11196–11199. DOI: 10.1021/acssuschemeng.8b02535.
[4] Altiti, A. S.; Ma, X.; Zhang, L.; Ban, Y.; Franck, R. W.; Mootoo, R. W. Synthesis and
Biological Activities of C-Glycosides of KRN 7000 with Novel Ceramide Residues.
Carbohydr. Res. 2017, 443–444, 73–77. DOI: 10.1016/j.carres.2017.03.005.
[5] Fang, T.; Mo, K. F.; Boons, G. J. Stereoselective Assembly of Complex Oligosaccharides
Using Anomeric Sulfonium Ions as Glycosyl Donors. J. Am. Chem. Soc. 2012, 134,
7545–7552. DOI: 10.1021/ja3018187.
[6] Yang, Y. Y.; Ficht, S.; Brik, A.; Wong, C. H. Sugar-Assisted Ligation in Glycoprotein
Synthesis. J. Am. Chem. Soc. 2007, 129, 7690–7701. DOI: 10.1021/ja0708971.
[7] Taskova, R. M.; Kokubun, T.; Ryan, K. J.; Garnock-Jones, P. J.; Jensen, S. R. Iridoid and
Phenylethanoid Glucosides from Veronica lavaudiana. J. Nat. Prod. 2011, 74, 1477–1483.
DOI: 10.1021/np200233p.
[8] Malinowski, M.; Rowicki, T.; Guzik, P.; Wielechowska, M.; Sas, W. Synthesis of
Carbohydrate Mimetics by Intramolecular 1,3-Dipolar Cycloaddition of N-(3-
Alkenyl)nitrones Derived from Unprotected D-Aldopentoses. Eur. J. Org. Chem. 2018, 6,
763–771. DOI: 10.1002/ejoc.201701512.
[9] Gutmann, A.; Nidetzky, B. Switching Between O- and C-Glycosyltransferase Through
Exchange of Active-Site Motifs. Angew. Chem. Int. Ed. Engl. 2012, 51, 12879–12883. DOI:
10.1002/anie.201206141.
[10] Awad, L.; Madani, R.; Gillig, A.; Kolympadi, M.; Philgren, M.; Muhs, A.; Gerard, C.;
Vogel, P. A C-Linked Disaccharide Analogue of Thomsen-Friedenreich Epitope Induces a

6
B. SINGH ET AL.
Strong Immune Response in Mice. Chemistry. 2012, 18, 8578–8582. DOI: 10.1002/
chem.201200364.
[11] Koester, D. C.; Kriemen, E.; Werz, D. B. Flexible Synthesis of 2-deoxy-C-Glycosides and
(1!2)-, (1!3)-, and (1!4)-Linked C-Glycosides. Angew. Chem. Int. Ed. Engl. 2013, 52,
2985–2989. DOI: 10.1002/anie.201209697.
[12] Zhang, P.; Li, C.; Yang, H.; Wei, H.; Xia, Z.; Ma, D.; Chen, H.; Wang, K.; Li, X. A
Convenient Synthesis of Novel aza-C-Disaccharide Analogues. Carbohydr. Res. 2014, 398,
36–39. DOI: 10.1016/j.carres.2014.05.016.
[13] Nolen, E. G.; Li, L.; Waynant, K. V. Synthesis of b-C-GlcNAc Ser from b-C-Glc Ser. J.
Org. Chem. 2013, 78, 6798–6801. DOI: 10.1021/jo401044x.
[14] Kitamura, K.; Ando, Y.; Matsumoto, T.; Suzuki, K. Total Synthesis of Aryl C-Glycoside
Natural Products: Strategies and Tactics. Chem. Rev. 2018, 118, 1495–1598. DOI: 10.1021/
acs.chemrev.7b00380.
[15] Sudhakar, G.; Raghavaiah, J. Total Synthesis of Varitriol, Varioxirane, and Enantiomer of
the Proposed Biosynthetic Precursor. J. Org. Chem. 2013, 78, 8840–8846. DOI: 10.1021/
jo4011766.
[16] Caletkovd, O.; Ldsikova, A.; Hajduch, M.; Dzubak, P.; Graczaa, T. Synthesis and antitu-
mour activity of varitriol and its analogues. ARKIVOC. 2012, 6, 365–383.
[17] Zeng, J.; Vedachalam, S.; Xiang, S.; Liu, X. Direct C-Glycosylation of
Organotrifluoroborates with Glycosyl Fluorides and Its Application to the Total Synthesis
of (þ)-Varitriol. Org. Lett. 2011, 13, 42–45. DOI: 10.1021/ol102473k.
[18] Brichacek, M.; Batory, L. A.; McGrath, N. A.; Njardarson, J. T. The Strategic Marriage of
Method and Motif. Total Synthesis of Varitriol. Tetrahedron. 2010, 66, 4832–4840. DOI:
10.1016/j.tet.2010.03.038.
[19] Ghosh, S.; Pradhan, T. K. Stereoselective Total Synthesis of (þ)-Varitriol, (-)-Varitriol, 5’-
Epi-(þ)-Varitriol, and 4’-Epi-(-)-Varitriol from D-Mannitol. J. Org. Chem. 2010, 75,
2107–2110. DOI: 10.1021/jo100001p.
[20] Kumar, V.; Shaw, A. K. First Total Synthesis of (þ)-Varitriol. J. Org. Chem. 2008, 73,
7526–7531. DOI: 10.1021/jo8013534.
[21] McAllister, G. D.; Robinson, J. E.; Taylor, R. K. The Synthesis of (ꢁ)-Varitriol and (ꢁ)-30-
€
Epi-Varitriol via a Ramberg–Backlund Route. Tetrahedron. 2007, 63, 12123–12130. DOI:
10.1016/j.tet.2007.09.057.
ꢀ
ꢀ
ꢀ
[22] Kaszas, T.; Toth, M.; Langer, P.; Somsak, L. C -Glycosyl Styrene Type Compounds by Pd-
Catalyzed Cross-Coupling Reactions of Anhydro-Aldose Tosylhydrazones with Benzyl
Bromides. Adv. Synth. Catal. 2019, 361, 105–117. ꢁ DOI: 10.1002/adsc.201801059.
[23] Zhu, F.; Rodriguez, J.; O’Neill, S.; Walczak, M. A. Acyl Glycosides through Stereospecific
Glycosyl Cross-Coupling: Rapid Access to C(sp3)-Linked Glycomimetics. ACS Cent Sci.
2018, 4, 1652–1662. DOI: 10.1021/acscentsci.8b00628.
[24] Liu, J.; Gong, H. Stereoselective Preparation of a- C -Vinyl/Aryl Glycosides via Nickel-
Catalyzed Reductive Coupling of Glycosyl Halides with Vinyl and Aryl Halides. Org. Lett.
2018, 20, 7991–7995. DOI: 10.1021/acs.orglett.8b03567.
[25] Khatri, V.; Kumar, A.; Singh, B.; Malhotra, S.; Prasad, A. K. Synthesis of b-C-
Glycopyranosyl Aldehydes and 2,6-Anhydro-Heptitols. J. Org. Chem. 2015, 80,
11169–11174. DOI: 10.1021/acs.joc.5b01933.
[26] Zeng, J.; Ma, J.; Xiang, S.; Cai, S.; Liu, X. Stereoselective b-C-Glycosylation by a
Palladium-Catalyzed Decarboxylative Allylation: Formal Synthesis of Aspergillide A.
Angew. Chem. Int. Ed. Engl. 2013, 52, 5134–5137. DOI: 10.1002/anie.201210266.
[27] Anand, N.; Upadhyaya, K.; Ajay, A.; Mahar, R.; Shukla, S. K.; Kumar, B.; Tripathi, R. P. A
Strategy for the Synthesis of Anthraquinone-Based aryl-C-Glycosides. J. Org. Chem. 2013,
78, 4685–4696. DOI: 10.1021/jo302589t.
[28] Gong, H.; Gagne, M. R. Diastereoselective Ni-Catalyzed Negishi Cross-Coupling Approach
to Saturated, Fully Oxygenated C-Alkyl and C-Aryl Glycosides. J. Am. Chem. Soc. 2008,
130, 12177–12183. DOI: 10.1021/ja8041564.

R
SYNTHETIC COMMUNICATIONSV
7
[29] Stork, G.; Suh, H. S.; Kim, G. The Temporary Silicon Connection Method in the Control
of Regio- and Stereochemistry. Applications to Radical-Mediated Reactions. The
Stereospecific Synthesis of C-Glycosides. J. Am. Chem. Soc. 1991, 113, 7054–7056. DOI:
10.1021/ja00018a063.
[30] Bamford, W. R.; Stevens, T. S. The decomposition of toluene-p-sulphonylhydrazones by
alkali. J. Chem. Soc. 1952, 4735–4740. DOI: 10.1039/jr9520004735.
[31] Xiao, Q.; Zhang, Y.; Wang, J. Diazo Compounds and N-Tosylhydrazones: Novel Cross-
Coupling Partners in Transition-Metal-Catalyzed Reactions. Acc. Chem. Res. 2013, 46,
236–247. DOI: 10.1021/ar300101k.
[32] Liu, H.; Wei, Y.; Cai, C. Hypervalent-Iodine(Iii) Oxidation of Hydrazones to Diazo
Compounds and One-Pot Nickel(ii)-Catalyzed Cyclopropanation. New J. Chem. 2016, 40,
674–678. DOI: 10.1039/C5NJ02378E.
[33] Feng, W.; Fang, Z.; Yang, J.; Zheng, B.; Jiang, Y. Microwave-Assisted Efficient Synthesis of
Aryl Ketone b-C-Glycosides from Unprotected Aldoses. Carbohydr. Res. 2011, 346,
352–356. DOI: 10.1016/j.carres.2010.11.027.
[34] (a) Shapiro, R. H.; Lipton, M. F.; Kolonko, K. J.; Buswell, R. L.; Capuano, L. A.
Tosylhydrazones and Alkyllithium Reagents: More on the Regiospecificity of the Reaction
and the Trapping of Three Intermediates. Tetrahedron Lett. 1975, 16, 1811–1814. DOI:
10.1016/S0040-4039(00)75263-4. (b) Adlington, R. M.; Barrett, A. G. M. Recent
Applications of the Shapiro Reaction. Acc. Chem. Res. 1983, 16, 55–59.