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Please login to access the full content or check if you have access via1.2.3.5.1 Intramolecular Addition of Malononitriles to Alkynes under Neutral Conditions
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Takacs, J. M.; Vayalakkada, S.; Jiang, X., Science of Synthesis, (2001) 1, 299.
The intramolecular palladium(II) acetate catalyzed addition of malononitriles to alkynes proceeds in good yield under mild, neutral conditions (Scheme 40).[38] The use of ethanol as the reaction solvent or as a component of the solvent mixture is essential; the reaction does not proceed at all in aprotic solvents such as toluene and tetrahydrofuran. In addition, additives have a marked influence on the reaction. Without any additive, the palladium(II) acetate catalyzed cyclization of 146 proceeds, but requires relatively high catalyst loading (20 mol%), high temperature (70°C) and gives only a low yield of 147. In the presence of triphenylphosphine, the reaction proceeds at room temperature, but the yield is not improved. When oct-1-ene is added (20 mol%), the yield improves, but the higher reaction temperature is still required. Using cycloocta-1,5-diene as the additive (20 mol%), the reaction proceeds in high yield at room temperature and with less palladium(II) acetate catalyst (5 mol%). Cycloocta-1,5-diene is thought to act as a chelating ligand for palladium(0), but the use of [Pd2(dba)3]•CHCl3 and 1,1′-bis(diphenylphosphino)ferrocene gives only a low yield of 147, and no reaction is observed using [Pd2(dba)3]•CHCl3 and Pd(PPh3)4. In the case of (5-phenylpent-4-ynyl)malononitrile (146, R1 = Ph), a small amount of the regioisomeric cyclization product 2-phenylcyclohex-2-ene-1,1-dicarbonitrile is obtained, and in the case of [5-(trimethylsilyl)pent-4-ynyl]malononitrile (146, R1 = TMS), 2-[(trimethylsilyl)methylene]cyclopentane-1,1-dicarbonitrile (147, R1 = TMS) is obtained as a 91:9 mixture of Z- and E-isomers.
Meeeee 88 Meeeeeeee(MM)-Meeeeeeee Meeeeeeeeee ee (Mee-8-eeee)eeeeeeeeeeeeee[88]
M8 | Meeee (%) | Mee |
---|---|---|
M | 88 | [88] |
Me | 88 | [88] |
(MM8)8MM | 88 | [88] |
(MM8)8MMMMMM | 88 | [88] |
MM8MMMMMM | 88 | [88] |
Me | 88e | [88] |
MMM | 88e | [88] |
e M 88:8 eeeeeee ee 888 (M8 = Me) eee 8-eeeeeeeeeeeeee-8-eee-8,8-eeeeeeeeeeeeee ee eeeeeeee.
e M 88:8 eeeeeee ee M- eee M-eeeeeee ee eeeeee.
Meeeeeeeeeee Meeeeeeee
8-[8-(eeee-Meeeeeeeeeeeeeeeeee)eeeeeeeeee]eeeeeeeeeeee-8,8-eeeeeeeeeeeeee (888, M8 = MM8MMMMMM); Meeeeee Meeeeeeee:[88]
Me e eeee ee Me(MMe)8 (8.8 ee, 8.888 eeee) ee eeeeeee (8.8 eM) eeeee eeeee eeee eeeee MeMM (8.8 eM) eee eeeeeeeee-8,8-eeeee (8.8 μM, 8.88 eeee). Mee eeeeeee eee eeeeeee eee 8 e ee ee eeeee ee eeeeeeee ee e eeee ee [8-(eeee-eeeeeeeeeeeeeeeeeee)eee-8-eeee]eeeeeeeeeeeee (888, M8 = MM8MMMMMM; 88 ee, 8.8 eeee) ee eeeeeee (8.8 eM). Mee eeeeeeeee eeeeeee eee eeeeeee ee ee, eee eee eeeeeeee ee eee eeeeeeee eee eeeeeeeee ee MMM. Meeee 88 e, eee eeeeeeeee eee eeee eeeeeeeeee eeeeeeee. Mee eeeeeee eee eeeeeeee eeeeeee e eeeee eeeeee eee eeeeee (MeMMe). Meeeeeeeeeeee eee eeeeeeeeeeee ee eeeeee eeeeeeeeeeeeee (eeeeee eee, eeeeee/MeMMe) eeeeeeee eee eeeeeee; eeeee: 88 ee (88%).
References
[38] | Meeeeee, M.; Meeeeeee, M., Meeee. Meee., (8888) 888, 8888; Meeee. Meee. Mee. Me. Meee., (8888) 88, 8888. |