Synthesis of enones
Highly regioselective vinylation of electron-rich olefins by halostyrenes is effected by palladium catalysis with either mono- or bidentate phosphines in DMSO as solvent. The use of hemilabile 1,3-bis(diphenylphosphino)propane monoxide as a ligand led to faster reactions of more challenging 2-substituted vinyl ethers and reduced Pd loadings.
M. McConville, O. Saidi, J. Blacker, J. Xiao, J. Org. Chem., 2009, 74, 2692-2698.
A new, efficient protocol for the highly stereoselective one-pot synthesis of (E)-styryl ketones from styrenes is based on sequential ruthenium-catalyzed silylative coupling-rhodium-catalyzed desilylative acylation reactions.
P. Pawluć, J. Szudkowska, G. Hreczycho, B. Marciniec, J. Org. Chem., 2011, 76, 6438-6441.
Photoredox catalysis enables a domino-fluorination-protodefluorination decarboxylative cross-coupling of α-keto acids with styrene to provide α,β-unsaturated ketones under mild conditions.
M. Zhang, J. Xi, R. Ruzi, N. Li, Z. Wu, W. Li, C. Zhu, J. Org. Chem., 2017, 82, 9305-9311.
A silver-catalyzed double-decarboxylative protocol enables an efficient and pratical construction of chalcone derivatives via cascade coupling of substituted α-keto acids with cinnamic acids under mild and environmentally benign aqueous conditions.
N. Zhang, D. Yang, W. Wei, L. Yuan, F. Nie, L. Tian, H. Wang, J. Org. Chem., 2015, 80, 3258-3263.
A Fe-mediated decarboxylative cross-coupling reaction between α-oxocarboxylic acids and acrylic acids in aqueous solution provides an efficient and expeditious approach to α,β-unsaturated carbonyl compounds. This transformation offers a wide substrate scope and good functional group compatibility utilizing inexpensive and easily accessible reagents. Mechanism studies suggest that a free radical pathway is involved.
Q. Jiang, J. Jia, B. Xu, A. Zhao, C.-C. Guo, J. Org. Chem., 2015, 80, 3586-3596.
A catalyzed formal hydroacylation of allenes with acid chlorides proceeds with commercially available Pd(OAc)2 as catalyst and HSi(iPr)3 as reducing reagent to yield the corresponding α,β-unsaturated ketones regio- and stereoselectively.
T. Fujihara, K. Tatsumi, J. Terao, Y. Tsuji, Org. Lett., 2013, 15, 2286-2289.
After treatment with bismesitylmagnesium, a range of tosylhydrazones furnishes exceptionally high incorporation of the introduced electrophiles and good yields of the functionalized styrenes. At conveniently accessible temperatures and with a comparably small excess of base reagent and electrophile (for example 1.05 equiv of Weinreb amides), this modified Shapiro reaction offers an efficient alternative to the lithium-mediated process.
W. J. Kerr, A. J. Morrison, M. Pazicky, T. Weber, Org. Lett., 2012, 14, 2250-2253.
In a method for the Friedel-Crafts-type insertion reaction of acetylene with acid chlorides in chloroaluminate ionic liquids, the use of ionic liquids not only serves to avoid the use of carbon tetrachloride or 1,2-dichloroethane but also suppresses side reactions, and enables a simpler purification procedure, giving a range of aromatic and aliphatic β-chlorovinyl ketones in high yield and purity.
D. J. M. Snelders, P. J. Dyson, Org. Lett., 2011, 13, 4048-4051.
Iridium complexes show high catalytic activity in regio- and stereoselective intermolecular additions of acid chlorides to terminal alkynes to afford valuable (Z)-β-chloro-α,β-unsaturated ketones. Whereas a N-heterocyclic carbene (NHC) is an efficient ligand for the addition of aroyl chlorides, dicyclohexyl(2-methylphenyl)phosphine (PCy2(o-Tol)) enables the reaction of aliphatic acid chlorides.
T. Miura, T. Biyajima, T. Fujii, M. Murakami, J. Am. Chem. Soc., 2012, 134, 194-196.
A copper-promoted reaction of 1-alkynes with α-carbonyl aldehydes in the presence of morpholine enables an efficient and highly regio- and stereoselective synthesis of E-1,2-dicarbonyl-3-ene derivatives.
S. Chen, Y. Li, H. Zhao, B. Li, J. Org. Chem., 2014, 79, 4137-4141.
1-Siloxy-1-alkenylcopper species were generated by 1,2-Csp2-to-O silyl migration of the copper enolates of acyltriphenylsilanes. The alkenylcopper species reacted with methyl, benzyl, allylic, tributylstannyl halides and in the presence of Pd(0) catalyst with aryl and alkenyl iodides to give geometrically pure (Z)-enol silyl ethers.
A. Tsubouchi, K. Onishi, T. Takeda, J. Am. Chem. Soc., 2006, 128, 14268-14269.
A 1,4-dipolar intermediate generated from pyridine and dimethyl acetylenedicarboxylate reacted with aldehydes to give 2-benzoylfumarates via the elimination of pyridine, whereas with N-tosylimines as dipolarophiles the reaction afforded highly substituted 1-azadienes.
V. Nair, A. R. Sreekanth, N. Abhilash, A. T. Biju, B. R. Devi, R. S. Menon, N. P. Rath, R. Srinivas, Synthesis, 2003, 1895-1902.
A nickel-catalyzed reductive coupling between vinyl triflates and acid fluorides provides an efficient access to various enones. The reaction avoids the use of acyl or vinyl metallic reagents, proceeds with a broad range of acid fluorides and cyclic vinyl triflates, and tolerates several functional groups.
F.-F. Pan, P. Guo, C.-L. Li, P. Su, X.-Z. Shu, Org. Lett., 2019, 21, 3701-3705.