Green Chemistry
Paper
reused five times with satisfactory yield without a significant petrol n-hexane/ethyl acetate (3 : 1–10 : 1) as the eluent to give
loss of its activity. Moreover, this reaction could be carried out product 3.
under solar light irradiation and is applicable for large-scale
reactions. This reaction system allowed accessing a variety of
products in moderate to high yields. These features make this Conflicts of interest
reaction a potential green and sustainable approach for both
There are no conflicts to declare.
academic and industrial applications.
Acknowledgements
Experimental
The authors gratefully acknowledge the National Natural
Science Foundation of China (no. 21808085), the China
Postdoctoral Science Foundation (2018M630519) and the
Postdoctoral Science Foundation of Jiangsu Province, China
(1701096B).
Instruments and reagents
1H NMR spectra were recorded on a Bruker DRX (400 MHz)
and 13C NMR spectra were recorded on a Bruker DRX
(100 MHz) spectrometer, using CDCl3 as the solvent with tetra-
methylsilane (TMS) as the internal standard at room tempera-
ture. Chemical shifts (δ) are given in ppm relative to TMS, and
the coupling constants J are given in Hz. Mass spectra were
recorded on a Finnigan TSQ Quantum-MS instrument in the
electrospray ionization (ESI) mode. Elemental analyses were
performed on a Yanagimoto MT3CHN recorder. All reactions
were carried out in oven-dried glassware under a nitrogen
atmosphere, unless stated otherwise. For quantitative flash
chromatography, technical grade solvents were used. All
chemicals were commercially available and used without
further purification. Analytical thin-layer chromatography was
performed on glass plates precoated with silica gel impreg-
nated with a fluorescent indicator (254 nm). The plates were
visualized by exposure to ultraviolet light. All solvents were
obtained from commercial suppliers. Diazonium salts 1a–1k
were prepared according to the literature.16
Notes and references
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Experimental method
Synthesis of mpg-C3N4.15 5 g of cyanamide and 12.5 g of
LUDOX HS40 silica were mixed together until complete dis-
solution of cyanamide. The mixture was heated in an oil bath
at 100 °C upon stirring for 3 h until the removal of water and
the formation of a white solid. The powder was then ground in
a mortar, transferred into a crucible and heated under air at
2.3 °C min−1 (4 h) up to 550 °C and then treated at 550 °C for
4 h. The as-obtained yellow powder was ground in a mortar
and then stirred in a 4 mol per L NH4HF2 solution for 24 h to
remove the silica template. The dispersion was filtered, and
then the precipitate was washed with water and ethanol. After
filtering, the yellow powder was dried under vacuum at 100 °C
overnight.
Preparation of racemic alcohols (3). A 25 mL clean and dry
Schlenk reaction tube with a magnetic stirring rotor was
equipped with diazoniumtetrafluoroborate (0.5 mmol), alkene
(0.6 mmol), mpg-C3N4 (20 mg) and H2O (3 mL). The mixture
was irradiated with a Xe lamp (250 W) and stirred at r.t. under
a nitrogen atmosphere for 4 h. The distance of the reaction
vial from light was about 10 centimeters. After the reaction,
mpg-C3N4 was filtered out of the mixture, and the solvent was
removed under reduced pressure. Purification of the crude
product was achieved by flash column chromatography using
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Green Chem.