10.1002/ejoc.201900143
European Journal of Organic Chemistry
COMMUNICATION
Product formation was observed in all cases. While, TPP and
Rose Bengal produced only trace amounts of the desired
glycoside, Cr(dppd)2BF4 gave a 30% yield of 3c. Although the
efficiency of all sensitizers is much lower compared to I2, the
results still provide mechanistic insights. The chromium complex
Prof. Katja Heinze (Mainz) and her group for providing
Cr(ddpd)2BF4 for screening purposes. We also thank Lisa Marie
Kammer and Alexander Lipp (both Mainz) for helpful discussions.
We thank Dr. Johannes C. Liermann (Mainz) for NMR
spectroscopy and Dr. Christopher Kampf (Mainz) for mass
spectrometry.
3
can sensitize O2 upon irradiation while a direct SET from the
thioglycoside is thermodynamically not feasible.[25] Thus, O-
1
glycoside formation through an SET-mechanism from O2 could
Keywords: Photochemistry, Carbohydrate Chemistry, Iodine,
also occur with I2 as a triplet sensitizer (Scheme 4, lower pathway). Visible Light, Glycosylation.
Conclusions
References
[1]
a) J. W. Tucker, C. R. J. Stephenson, J. Org. Chem. 2012, 77, 1617-
In summary, a mild and catalytic activation of thioglycosides with
low loadings of molecular iodine as the catalyst under irradiation
with visible light was developed. The reported method tolerates a
variety of alcohols for O-glycosylation in yields up to 95%. Both
disarmed and armed thioglycosides could be reacted in this
robust transformation that requires only oxygen as cheap and
environmental friendly terminal oxidant. As expected, the
anomeric selectivity is low for armed donors while a 2-O-acyl
group offers full stereocontrol. Thioglycoside activation is likely to
proceed through a combination of an ionic pathway and a direct
SET pathway. Supporting mechanistic studies also suggest that
electronically excited iodine is not only involved in its own
regeneration but also directly activates thioglycosides with a
higher efficiency compared to the ground state. The discovered
photoactivation can likely be extended to other reactions where
iodine acts as an electrophilic reagent or catalyst.
1622; b) M. H. Shaw, J. Twilton, D. W. C. MacMillan, J. Org. Chem.
2016, 81, 6898-6926; c) C.-S. Wang, P. H. Dixneuf, J.-F. Soulé,
Chem. Rev. 2018, 118, 7532-7585.
a) C. K. Prier, D. A. Rankic, D. W. C. MacMillan, Chem. Rev. 2013,
113, 5322-5363; b) S. Fukuzumi, K. Ohkubo, Chem. Sci. 2013, 4,
561-574; c) N. A. Romero, D. A. Nicewicz, Chem. Rev. 2016, 116,
10075-10166.
R. L. Brown, W. Klemperer, J. Chem. Phys. 1964, 41, 3072-3089.
a) L. F. Meadows, R. M. Noyes, J. Am. Chem. Soc. 1960, 82, 1872-
1876; b) J. Olmsted, G. Karal, J. Am. Chem. Soc. 1972, 94, 3305-
3310; c) G. W. Luther, J. Wu, J. B. Cullen, in Aquatic Chemistry, Vol.
244, American Chemical Society, 1995, pp. 135-155.
[2]
[3]
[4]
[5]
[6]
P. Becker, T. Duhamel, C. J. Stein, M. Reiher, K. Muñiz, Angew.
Chem. 2017, 56, 8004-8008.
Y. Liu, B. Wang, X. Qiao, C.-H. Tung, Y. Wang, ACS Catalysis 2017,
4093-4099.
[7]
[8]
Y. Sudo, E. Yamaguchi, A. Itoh, Org. Lett. 2017, 19, 1610-1613.
a) R. Das, B. Mukhopadhyay, ChemistryOpen 2016, 5, 401-433; b)
Y. Yang, B. Yu, Chem. Rev. 2017.
a) M. L. Wolfrom, K. Anno, J. Am. Chem. Soc. 1953, 75, 1038-1039;
b) R. J. Ferrier, R. W. Hay, N. Vethaviyasar, Carbohydr. Res. 1973,
27, 55-61.
[9]
[10]
a) S. G. Durón, T. Polat, C.-H. Wong, Org. Lett. 2004, 6, 839-841;
b) J. D. C. Codee, R. E. J. N. Litjens, L. J. van den Bos, H. S.
Overkleeft, G. A. van der Marel, Chem. Soc. Rev. 2005, 34, 769-
782; c) C. Wang, H. Wang, X. Huang, L.-H. Zhang, X.-S. Ye, Synlett
2006, 2006, 2846-2850; d) J. Tatai, P. Fügedi, Org. Lett. 2007, 9,
4647-4650; e) G. Lian, X. Zhang, B. Yu, Carbohydr. Res. 2015, 403,
13-22; f) M. Mende, C. Bednarek, M. Wawryszyn, P. Sauter, M. B.
Biskup, U. Schepers, S. Bräse, Chem. Rev. 2016, 116, 8193-8255.
a) W. J. Wever, M. A. Cinelli, A. A. Bowers, Org. Lett. 2013, 15, 30-
33; b) M. Nakanishi, D. Takahashi, K. Toshima, Org. Biomol. Chem.
2013, 11, 5079-5082; c) M. Spell, X. Wang, A. E. Wahba, E. Conner,
J. Ragains, Carbohydr. Res. 2013, 369, 42-47; d) R. Iwata, K. Uda,
D. Takahashi, K. Toshima, Chem. Commun. 2014, 50, 10695-
10698; e) R.-Z. Mao, F. Guo, D.-C. Xiong, Q. Li, J. Duan, X.-S. Ye,
Org. Lett. 2015, 17, 5606-5609; f) M. L. Spell, K. Deveaux, C. G.
Bresnahan, B. L. Bernard, W. Sheffield, R. Kumar, J. R. Ragains,
Angew. Chem. Int. Ed. 2016, 55, 6515-6519; g) T. Kimura, T. Eto,
D. Takahashi, K. Toshima, Org. Lett. 2016, 18, 3190-3193; h) R.-Z.
Mao, D.-C. Xiong, F. Guo, Q. Li, J. Duan, X.-S. Ye, Org. Chem.
Front. 2016, 3, 737-743; i) Y. Yu, D.-C. Xiong, R.-Z. Mao, X.-S. Ye,
J. Org. Chem. 2016, 81, 7134-7138; j) R. Sangwan, P. K. Mandal,
RSC Advances 2017, 7, 26256-26321; k) P. Wen, D. Crich, Org.
Lett. 2017, 19, 2402-2405.
Experimental Section
General procedure for iodine catalyzed glycosylation: The
thioglycoside (0.158 mmol, 1.00 eq.) was dissolved in anhydrous
acetonitrile (1.00 mL) under argon atmosphere in a reaction
vessel that was sealed with a rubber septum. Iodine (0.004 mmol,
2.5 mol%) was added and the reaction mixture was stirred until
iodine was completely dissolved. The reaction vessel was flooded
with oxygen from an oxygen gas cylinder for 1 minute. The alcohol
(0.316 mmol, 2.00 eq.) was added and the reaction vessel was
placed above a stir plate with stirring at high rpm. The reaction
was irradiated by a 12W warm white LED bulb with 5 cm distance
between the bulb and the reaction vessel. The borders of the stir
plate were covered with aluminium to shield and reflect the light.
The reaction mixture was irradiated for 24 h. Afterwards the
reaction mixture was diluted with EtOAc and transferred to a
separatory funnel. The organic layer was extracted with sat.
thiosulfate-solution, sat. NaHCO3-solution and brine. The organic
layer was dried over Na2SO4, filtered and all volatiles were
removed in vacuo. The crude product was purified by column
chromatography (SiO2, cHex/EtOAc).
[11]
[12]
[13]
[14]
a) H. Uchiro, T. Mukaiyama, Chem. Lett. 1997, 26, 121-122; b) M.
Goswami, D. C. Ashley, M.-H. Baik, N. L. B. Pohl, J. Org. Chem.
2016, 81, 5949-5962; c) M. M. Nielsen, C. M. Pedersen, Chem. Rev.
2018, 118, 8285-8358.
a) K. P. Ravindranathan Kartha, M. Aloui, R. A. Field, Tett. Lett.
1996, 37, 5175-5178; b) K. P. R. Kartha, P. Cura, M. Aloui, S. K.
Readman, T. J. Rutherford, R. A. Field *, Tetrahedron: Asymmetry
2000, 11, 581-593.
K. Waszkowiak, K. Szymandera-Buszka, Int. J. Food Sci. Technol.
2008, 43, 895-899.
[15]
[16]
L. Botella, C. Nájera, J. Organomet. Chem. 2002, 663, 46-57.
D. R. Mootoo, P. Konradsson, U. Udodong, B. Fraser-Reid, J. Am.
Chem. Soc. 1988, 110, 5583-5584.
Acknowledgments
[17]
The formation of this hydrolysis product presumably results from
opening of the 2-hydroxydioxolane intermediate produced by attack
of water onto the dioxolenium intermediate. Water is a co-product of
the oxidative glycoslytion and may attack the dioxolenium
Support by the German Research Foundation (SFB 1066) and the
LESSING initiative of JGU is gratefully acknowledged. We thank
This article is protected by copyright. All rights reserved.