Synthesis of Allenes by Hydroalkylation of 1,3-Enynes with Ketones Enabled by Cooperative Catalysis
Maxwell Eaton, Yuping Dai, Ziyong Wang, Bo Li, Walid Lamine, Karinne Miqueu* and Shih-Yuan Liu*
*Université de Pau et des Pays de l’Adour, 64053 Pau Cedex 09, France; Boston College, Massachusetts 02467-3860, United States,
Email: karinne.miqueu
univ-pau.fr, shihyuan.liubc.edu
M. Eaton, Y. Dai, Z. Wang, B. Li, W. Lamine, K. Miqueu, S.-Y. Liu, J. Am. Chem. Soc., 2023, 145, 21638-21645.
DOI: 10.1021/jacs.3c08151
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Abstract
The combination of Pd(0)Senphos/B(C6F5)3/NR3 catalyzes an addition of ketones to 1,3-enynes to provide allenes. A wide range of aryl- and aliphatic ketones undergo addition to various 1,3-enynes in high yields at room temperature. The mechanism includes a rate-determining outer-sphere proton transfer, which was corroborated by DFT calculations.
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proposed mechanism
General Procedure for Hydroalkylation of 1,3-Enynes
To an oven-dried 4 mL vial containing a stir bar in a nitrogen-filled glovebox was added (COD)Pd(CH2TMS)2 (2.6 mg, 6.8 μmol, 2.5 mol%), ligand (3.5 mg, 8.1 μmol, 3.0 mol%), and toluene (0.5 mL). The mixture was allowed to stir for 5 minutes before adding enyne (0.27 mmol, 1.0 equiv.), B(C6F5)3 (13 mg, 0.027 mmol, 10.0 mol%), PMP (4.2 mg, 0.027 mmol, 10.0 mol%), and ketone (0.54 mmol, 2.0 equiv.). The vial was capped, removed from the glovebox, and allowed to stir at room temperature for 4 hours. At the conclusion of the reaction, the mixture was then passed through a short silica plug eluting with Et2O (3 x 2 mL). The mixture was then concentrated, and the crude material was purified by silica gel column chromatography to afford the allene product (CH2Cl2/hexanes or Et2O/hexanes).
Key Words
ID: J48-Y2023
