Synthesis of Indoles by Palladium-Catalyzed Reductive Cyclization of β-Nitrostyrenes with Phenyl Formate as a CO Surrogate
Abstract
:1. Introduction
2. Results and Discussion
Optimization of the Reaction Conditions
3. Materials and Methods
3.1. General Procedures
3.2. Apparatus
3.3. General Methods for Catalytic Reactions
3.4. Characterization Data for Indoles
4. Conclusions
Supplementary Materials
Author Contributions
Funding
Acknowledgments
Conflicts of Interest
References
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Entry | Phen (mol%) | T (°C) | Base | Base Amount (mmol) | Solvent | Conv.% 2 | Select.% 3 |
---|---|---|---|---|---|---|---|
1 | 2.5 | 140 | Et3N | 0.29 | CH3CN | 80 | 39 |
2 | 10 | 140 | Et3N | 2.30 | CH3CN | >99 | 40 |
3 | 10 | 140 | Et3N | 2.30 | THF | 85 | 30 |
4 | 10 | 140 | Et3N | 2.30 | DMF | >99 | 41 |
5 | 10 | 140 | Et3N | 2.30 | C6H5CH3 | 52 | 12 |
6 | 10 | 140 | Et3N | 2.30 | CH3OH | 85 | 9 |
7 4 | 10 | 140 | - | - | CH3CN | ~0 | 0 |
8 5 | 10 | 140 | Et3N | 2.30 | CH3CN | 61 | 0 |
9 | 10 | 120 | Et3N | 0.29 | CH3CN | 32 | 31 |
10 | 10 | 120 | Py | 0.29 | CH3CN | <1 | <1 |
11 | 10 | 150 | Py | 0.29 | CH3CN | 17 | 18 |
12 | 10 | 120 | NaOAc | 0.29 | CH3CN | 62 | 17 |
13 | 10 | 120 | Na3PO4 | 0.29 | CH3CN | 78 | 7 |
14 6 | 10 | 140 | Et3N | 2.30 | CH3CN | >99 | 26 |
15 6 | 10 | 140 | Et3N | 0.29 | CH3CN | 95 | 28 |
16 7 | 10 | 140 | Et3N | 2.30 | CH3CN | >99 | 47 |
Entry | Pd (mol%) | Phen (mol%) | T (°C) | t (h) | Et3N (μL) | PhOC(O)H (μL) | Conv.% 2 | Select.% 3 |
---|---|---|---|---|---|---|---|---|
1 | 1 | 5 | 110 | 3 | 120 | 260 | >99 | 84 |
2 | 1 | 5 | 120 | 3 | 120 | 260 | >99 | 87 |
3 | 1 | 5 | 130 | 3 | 120 | 260 | >99 | 90 |
4 | 1 | 5 | 140 | 3 | 120 | 260 | >99 | 92 |
5 | 1 | 5 | 150 | 3 | 120 | 260 | >99 | 77 |
6 | 1 | 5 | 140 | 3 | 20 | 260 | >99 | 84 |
7 | 1 | 5 | 140 | 3 | 40 | 260 | >99 | 85 |
8 | 1 | 5 | 140 | 3 | 60 | 260 | >99 | 87 |
9 | 1 | 5 | 140 | 3 | 80 | 260 | >99 | 88 |
10 | 1 | 5 | 140 | 3 | 120 | 200 | 97 | 81 |
11 | 1 | 5 | 140 | 3 | 120 | 350 | >99 | 91 |
12 | 1 | 5 | 140 | 3 | 200 | 350 | >99 | 90 |
13 | 1 | 2.5 | 140 | 3 | 120 | 260 | 94 | 85 |
14 | 1 | 2.5 | 140 | 3 | 80 | 260 | >99 | 83 |
15 | 1 | 2.5 | 140 | 7 | 40 | 260 | >99 | 87 |
16 | 1 | 2.5 | 140 | 16 | 40 | 260 | >99 | 87 |
17 | 1 | 10 | 140 | 3 | 120 | 260 | >99 | 90 |
18 | 0.5 | 5 | 140 | 3 | 120 | 260 | >99 | 78 |
19 | 0.5 | 5 | 140 | 6 | 120 | 260 | >99 | 79 |
20 4 | 2 | 5 | 140 | 3 | 120 | 260 | >99 | 90 |
21 4 | 2 | 5 | 140 | 1.5 | 120 | 260 | >99 | 90 |
22 5 | 1 | 5 | 140 | 3 | 120 | 260 | >99 | 88 |
23 6 | 1 | 5 | 140 | 3 | 120 | 260 | >99 | 85 |
Entry | Substrate | Product | Yield 2 |
---|---|---|---|
1 3 | 43(47) 4 | ||
2 | 89(92) 4 | ||
3 | 66 | ||
4 | |||
5 | 49 | ||
6 | _ 5 | ||
7 | 67(1:2.5) | ||
8 | 70 | ||
9 | 71(1.3:1) | ||
10 | 47 | ||
11 | (34) 4 | ||
12 | _ 5 |
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Ferretti, F.; Fouad, M.A.; Ragaini, F. Synthesis of Indoles by Palladium-Catalyzed Reductive Cyclization of β-Nitrostyrenes with Phenyl Formate as a CO Surrogate. Catalysts 2022, 12, 106. https://doi.org/10.3390/catal12010106
Ferretti F, Fouad MA, Ragaini F. Synthesis of Indoles by Palladium-Catalyzed Reductive Cyclization of β-Nitrostyrenes with Phenyl Formate as a CO Surrogate. Catalysts. 2022; 12(1):106. https://doi.org/10.3390/catal12010106
Chicago/Turabian StyleFerretti, Francesco, Manar Ahmed Fouad, and Fabio Ragaini. 2022. "Synthesis of Indoles by Palladium-Catalyzed Reductive Cyclization of β-Nitrostyrenes with Phenyl Formate as a CO Surrogate" Catalysts 12, no. 1: 106. https://doi.org/10.3390/catal12010106