Synthesis of cyclohexanones
tert-Dodecanthiol-catalyzed generation of acyl radicals and their intramolecular addition to double bonds gave 2-substituted five- and six-membered cyclic ketones in good yields.
K. Yoshikai, T. Hayama, K. Nishimura, K.-I. Yamada, K. Tomioka, J. Org. Chem., 2005, 70, 681-683.
Substoichiometric amounts of a Gd(OTf)3 mediate the addition of tertiary carbon radicals generated from N-(acyloxy)phthalimide esters to cyclic α,β-unsaturated ketones and lactones. The reaction is accomplished by irradiation with visible light in the presence of Hantzsch ester without the use of a photosensitizer.
S. P. Pitre, T. K. Allred, L. E. Overman, Org. Lett., 2021, 23, 1103-1106.
A cationic cyclization enables the synthesis of cyclohexanones from alkynol or enyne derivatives with a terminal triple bond. Crucial for the success of the reaction are the use of tetrafluoroboric acid as a promoter of the cationic cyclization, and the selection of 1,1,1,3,3,3-hexafluoropropan-2-ol as solvent. This strategy can be extended to the biomimetic cationic cyclization of several terpene-derived polyenynes.
P. Alsonso, R. Fonteneda, P. Pardo, F. J. Fañanás, F. Rodríguez, Org. Lett., 2018, 20, 1659-1662.
A chiral Al(III)-N,N'-dioxide complex catalyzes an acyloin rearrangement of cyclic α-ketols to provide an array of optically active 2-acyl-2-hydroxy cyclohexanones in good yields with high enantioselectivities. Asymmetric isomerizations of acyclic α-hydroxy aldehydes and α-iminols were achieved as well under modified conditions.
L. Dai, X. Li, Z. Zeng, S. Dong, Y. Zhou, X. Liu, X. Feng, Org. Lett., 2020, 22, 5041-5045.
Enol esters can be epoxidized with high enantioselectivities using a fructose-derived chiral ketone as catalyst and Oxone as oxidant. A subsequent acid-catalyzed rearrangement can proceed through two distinct pathways, one with retention of configuration and the other with inversion. Whereas a strong acid favors retention of configuration, a weak acid favors inversion of configuration.
Y. Zhu, L. Shu, Y. Tu, Y. Shi, J. Org. Chem., 2001, 66, 1818-1826.
Under blue-light irradiation with 1,2,3,5-tetrakis(carbazol-9-yl)-4,6-dicyanobenzene as photocatalyst, silyl enol ethers reacted with alkenes in the presence of a small amount of water to afford α-alkylated products in very good yields. A thiol cocatalyst was found to expand the substrate scope of the reaction.
T. Hirata, Y. Ogasawara, Y. Yamashita, S. Kobayashi, Org. Lett., 2021, 23, 5693-5697.
Development of (Trimethylsilyl)ethyl Ester Protected Enolates and Applications in Palladium-Catalyzed Enantioselective Allylic Alkylation: Intermolecular Cross-Coupling of Functionalized Electrophiles
C. M. Reeves, D. C. Behenna, B. M. Stoltz, Org. Lett., 2014, 16, 2314-2317.
In the presence of PdCl2(MeCN)2, CuCl2, and PEG-400, various alkenyl β-keto esters and amides underwent a selective cyclization to give six-membered carbocycles in good to excellent yields. The PdCl2(MeCN)2/CuCl2/PEG-400 system could be recycled and reused five times without any loss of catalytic activity.
J.-H. Li, Q.-M. Zhu, Y. Liang, D. Yang, J. Org. Chem., 2005, 70, 5347-5349.
The reaction of β-keto esters with CF3CO2ZnCH2I provided the corresponding chain-extended products in moderate to good yields. α-Substituted acyclic β-keto esters reacted less efficiently than cyclic β-keto esters or simple β-keto esters.
S. Xue, Y.-K. Liu, L.-Z. Li, Q.-X. Guo, J. Org. Chem., 2005, 70, 8245-8247.
Ligand-free cationic Pd(II) catalyst is a highly active catalytic system for conjugate additions of boroxines to sterically hindered γ-substituted cyclohexenones in the presence of NaNO3 as an additive. More challenging γγ- and βγ-substrates also react well to produce products with quaternary centers in a highly diastereoselective fashion.
J. A. Jordan-Hore, J. N. Sanderson, A.-L. Lee, Org. Lett., 2012, 14, 2508-2511.
Pyrrolidinine-thioxotetrahydropyrimidinone derivatives were tested for their catalytic properties in various asymmetric organic transformations. These catalysts could efficiently catalyze the reactions in brine, without the use of organic solvent, and by employing an almost stoichiometric amount of reagents. Thus, the products were isolated by simple extractions in excellent yields, diastereoselectivities, and enantioselectivities.
N. Kaplaneris, G. Koutoulogenis, M. Raftopoulou, C. G. Kokotos, J. Org. Chem., 2015, 80, 5464-5473.
A fluorous (S)-pyrrolidine sulfonamide organocatalyst promotes highly enantio- and diastereoselective Michael addition reactions of ketones and aldehydes with nitroolefins in water. The organocatalyst is conveniently recovered from the reaction mixtures by fluorous solid-phase extraction and can be reused.
L. Zu, J. Wang, H. Li, W. Wang, Org. Lett., 2006, 8, 3077-3079.
Two new atropisomeric electron-poor chiral diphosphine ligand analogues of SYNPHOS were prepared, that allow a highly performant Rh-catalyzed asymmetric 1,4-addition of arylboronic acids to α,β-unsaturated carbonyl compounds at room temperature.
F. Berhal, O. Esseiva, C.-H. Martin, H. Tone, J.-P. Genet, T. Ayad, V. Ratovelomanana-Vidal, Org. Lett., 2011, 13, 2806-2809.
Cyclohexane-1,3-dione derivatives synthesis from unreactive acetone has been accomplished through a consecutive Michael-Claisen process. Furthermore, the scope of different carbonyl compounds was investigated and resulted with similar consecutive Michael-Claisen process for CDD synthesis. The reaction exhibited remarkable regioselectivity in Michael addition followed by Claisen cyclization.
D. Sharma, Bandna, A. K. Shil, B. Singh, P. Das, Synlett, 2012, 23, 1199-1204.
An AlCl3·MeNO2-mediated Dieckmann cyclization reaction of general synthetic utility enables direct access to complex 2-alkyl-1,3-dione building blocks from readily available dicarboxylic acid and acid chloride substrates. This method enables direct access to the chiloglottone plant pheromones from commercially available starting materials in a single synthetic transformation.
A. M. Armaly, S. Bar, C. S. Schindler, Org. Lett., 2017, 19, 3962-3965.
The use of acid chlorides as formal dianion linchpin reagents enables access to cyclic 2-alkyl- and 2-acyl-1,3-alkanediones from dicarboxylic acids. Mechanistic experiments confirm the role of acid chlorides as carbon dianion linchpin reagents and have led to a revised reaction mechanism for the aluminum(III)-mediated Dieckmann cyclization of dicarboxylic acids with acid chlorides.
A. M. Armaly, S. Bar, C. S. Schindler, Org. Lett., 2017, 19, 3958-3961.
A simple chiral primary amine catalyses a highly efficient reaction for the synthesis of both Wieland-Miescher ketone and Hajos-Parrish ketone as well as their analogues in high enantioselectivity and excellent yields. This procedure represents one of the most efficient methods for the synthesis of these versatile chiral building blocks even in gram scale with 1 mol% catalyst loading.
P. Zhou, L. Zhang, S. Luo, J.-P. Cheng, J. Org. Chem., 2012, 77, 2526-2530.