Categories: C=C Bond Formation >
Synthesis of allenes by 1,4-addition
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Recent Literature
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.
M. Eaton, Y. Dai, Z. Wang, B. Li, W. Lamine, K. Miqueu, S.-Y. Liu, J. Am. Chem. Soc.,
2023, 145, 21638-21645.
Conjugated enynes undergo selective 1,4-hydroamination under Pd catalysis to
deliver chiral allenes with pendant allylic amines. Several primary and
secondary aliphatic and aryl-substituted amines couple with a wide range of
mono- and disubstituted enynes in a nonenantioselective reaction where DPEphos
serves as the ligand. Benzophenone can be used as an ammonia surrogate.
N. J. Adamson, H. Jeddi, S. J. Malcolmson, J. Am. Chem. Soc.,
2019,
141, 8574-8583.
A 1,4-alkylcyanation of enynes with cyclic alcohol derivatives in the
presence of trimethylsilyl cyanide (TMSCN) under copper/photoredox dual
catalysis provides efficient access to functionalized allenes with easily
transformable aldehyde and cyano groups. The reactions proceeded smoothly under
mild conditions with broad functional groups tolerance.
Y. Pu, S. Ding, H. Zhao, Q. Xue, H. Zhang, X. Xie, Y. Shang, J. Wang, Org. Lett., 2024,
26,
1834-1839.
A practical, convenient, and highly regioselective copper-catalyzed
1,4-chlorotrifluoromethylation of 1,3-enynes affords chloro- and CF3-containing
tetrasubstituted allene derivatives with very good yield. A
1,4-bromotrifluoromethylation is also reported.
J. Huang, Y. Jia, X. Li, J. Duan, Z.-X. Jiang, Z. Yang, Org. Lett., 2021, 23,
2314-2319.
Cu(CH3CN)4BF4 catalyzes a radical
bis(trifluoromethylation) of alkynes and 1,3-enynes with Togni reagent II and
(bpy)Zn(CF3)2 at room temperature to afford the
corresponding 1,2-bis(trifluoromethylated) alkenes and
1,4-bis(trifluoromethylated) allenes in good yields. This protocol exhibits
broad substrate scope and excellent functional group compatibility.
H. Shen, H. Xiao, L. Zhu, C. Li, Synlett, 2020,
31,
41-44.