Synlett 2020; 31(19): 1919-1924
DOI: 10.1055/s-0040-1705948
cluster
Integrated Synthesis Using Continuous-Flow Technologies

Fine-Bubble–Slug-Flow Hydrogenation of Multiple Bonds and Phenols

Takuya Iio
a   Department of Engineering, Graduate School of Integrated Science and Technology, Shizuoka University, 3-5-1 Johoku, Hamamatsu, Shizuoka 432-8561, Japan
,
Kohei Nagai
a   Department of Engineering, Graduate School of Integrated Science and Technology, Shizuoka University, 3-5-1 Johoku, Hamamatsu, Shizuoka 432-8561, Japan
,
Tomoki Kozuka
b   Department of Applied Chemistry and Biochemical Engineering, Faculty of Engineering, Shizuoka University, 3-5-1 Johoku, Hamamatsu, Shizuoka 432-8561, Japan
,
Akhtar Mst Sammi
a   Department of Engineering, Graduate School of Integrated Science and Technology, Shizuoka University, 3-5-1 Johoku, Hamamatsu, Shizuoka 432-8561, Japan
,
Kohei Sato
a   Department of Engineering, Graduate School of Integrated Science and Technology, Shizuoka University, 3-5-1 Johoku, Hamamatsu, Shizuoka 432-8561, Japan
b   Department of Applied Chemistry and Biochemical Engineering, Faculty of Engineering, Shizuoka University, 3-5-1 Johoku, Hamamatsu, Shizuoka 432-8561, Japan
c   Graduate School of Science and Technology, Shizuoka University, 3-5-1 Johoku, Hamamatsu, Shizuoka 432-8561, Japan
,
Tetsuo Narumi
a   Department of Engineering, Graduate School of Integrated Science and Technology, Shizuoka University, 3-5-1 Johoku, Hamamatsu, Shizuoka 432-8561, Japan
b   Department of Applied Chemistry and Biochemical Engineering, Faculty of Engineering, Shizuoka University, 3-5-1 Johoku, Hamamatsu, Shizuoka 432-8561, Japan
c   Graduate School of Science and Technology, Shizuoka University, 3-5-1 Johoku, Hamamatsu, Shizuoka 432-8561, Japan
d   Research Institute of Green Science and Technology, Shizuoka University, 3-5-1 Johoku, Hamamatsu, Shizuoka 432-8561, Japan   Email: mase.nobuyuki@shizuoka.ac.jp
,
Nobuyuki Mase∗
a   Department of Engineering, Graduate School of Integrated Science and Technology, Shizuoka University, 3-5-1 Johoku, Hamamatsu, Shizuoka 432-8561, Japan
b   Department of Applied Chemistry and Biochemical Engineering, Faculty of Engineering, Shizuoka University, 3-5-1 Johoku, Hamamatsu, Shizuoka 432-8561, Japan
c   Graduate School of Science and Technology, Shizuoka University, 3-5-1 Johoku, Hamamatsu, Shizuoka 432-8561, Japan
d   Research Institute of Green Science and Technology, Shizuoka University, 3-5-1 Johoku, Hamamatsu, Shizuoka 432-8561, Japan   Email: mase.nobuyuki@shizuoka.ac.jp
› Author AffiliationsThis work was supported in part by JSPS KAKENHI Grant Numbers JP15H03844 and JP18H02012, and MEXT KAKENHI Grant Number JP18H04397.
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Abstract

We describe a promising method for the continuous hydrogenation of alkenes or alkynes by using a newly developed fine-bubble generator. The fine-bubble-containing slug-flow system was up to 1.4 times more efficient than a conventional slug-flow method. When applied in the hydrogenation of phenols to the corresponding cyclohexanones, the fine bubble–slug-flow method suppressed over-reduction. As this method does not require the use of excess gas, it is expected to be widely applicable in improving the efficiency of gas-mediated flow reactions.

Key words

flow reaction - gas–liquid reaction - hydrogenation - alkynes - alkenes - phenols

Supporting Information

    Supporting information for this article is available online at https://doi.org/10.1055/s-0040-1705948.
  • Supporting Information


Publication History

Received: 27 August 2020

Accepted after revision: 16 September 2020

Article published online:
21 October 2020

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  • References and Notes

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  • 15 Hydrogenation of Alkenes or Alkynes by the H2-FB-Slug-Flow Method: Typical Procedure A 500 mL Duran bottle was charged with a solution of the appropriate substrate 1 (8.28 mmol) in MeOH (400 mL). The reactor was charged with 10% Pd/C (1.1 g, 0.47 mmol) and placed in a column oven (CTO-10AC; Shimadzu, Japan) at 60 °C. The solution of 1 was delivered at a flow rate of 2.0 mL/min (residence time in the reactor = 35 s), and H2 gas was delivered at a flow rate of 1.0 mL/min (1 equiv). The pressure in the front of the reactor was set to approximately 4 MPa to generate FBs. After 30 min of operation at 60 °C, the reaction mixture was collected every 10 min and analyzed by GC-FID, without purification.