127154-52-3Relevant academic research and scientific papers
Highly Enantioselective Cobalt-Catalyzed Hydroboration of Diaryl Ketones
Liu, Wenbo,Guo, Jun,Xing, Shipei,Lu, Zhan
supporting information, p. 2532 - 2536 (2020/04/02)
A highly enantioselective cobalt-catalyzed hydroboration of diaryl ketones with pinacolborane was developed using chiral imidazole iminopyridine as a ligand to access chiral benzhydrols in good to excellent yields and ee. This protocol could be carried out in a gram scale under mild reaction conditions with good functional group tolerance. Chiral biologically active 3-substituted phthalide and (S)-neobenodine could be easily constructed through asymmetric hydroboration as a key step.
General Method for the Suzuki-Miyaura Cross-Coupling of Primary Amide-Derived Electrophiles Enabled by [Pd(NHC)(cin)Cl] at Room Temperature
Lei, Peng,Meng, Guangrong,Ling, Yun,An, Jie,Nolan, Steven P.,Szostak, Michal
supporting information, p. 6510 - 6513 (2017/12/26)
A general, highly selective method for the room temperature Suzuki-Miyaura cross-coupling of commonly encountered primary benzamides is reported. A combination of site-selective N,N-di-Boc-activation (tert-butoxycarbonyl activation) of the amide nitrogen with practical air- and moisture-stable, well-defined, and highly reactive [Pd(NHC)(cin)Cl] (NHC = N-heterocyclic carbene; cin = cinnamyl) provides a highly effective route to biaryl ketones from primary amides in high yields. For the first time, a TON of >1000 has been achieved in amide acyl cross-coupling.
Nickel-catalyzed diaryl ketone synthesis by N-C cleavage: Direct negishi cross-coupling of primary amides by site-selective N,N-Di-boc activation
Shi, Shicheng,Szostak, Michal
, p. 5872 - 5875 (2016/11/29)
A general Negishi acylation of primary amides enabled by a combination of site-selective N,N-di-Boc activation and nickel catalysis is reported for the first time. The reaction is promoted by a bench-stable, inexpensive Ni catalyst. The reaction shows excellent functional group compatibility, affording functionalized diaryl ketones by selective N-C cleavage. Most notably, this protocol represents the first amide cross-coupling by direct metal insertion of simple and readily available primary amides. The overall strategy by N,N-di-Boc activation/metal insertion is suitable for a broad range of coupling protocols via acylmetals. Mechanistic experiments suggest high reactivity of N,N-di-Boc activated 1° amides in direct amide C-N cross-couplings.
Dehydrative condensation of carbonyls with non-acidic methylenes enabled by light: Synthesis of benzofurans
Liu, Wenbo,Chen, Ning,Yang, Xiaobo,Li, Lu,Li, Chao-Jun
supporting information, p. 13120 - 13123 (2016/11/09)
Condensation of carbonyls with non-acidic methylenes such as those adjacent to heteroatoms and allylic types to generate CC bonds is challenging but highly desirable. Inventing novel methods that can accomplish such condensations can enrich synthetic chemists' toolbox. Herein, we report a simple, clean, and high yielding protocol promoted by light to achieve condensation of non-acidic methylenes with carbonyls. As examples to demonstrate the power of this methodology, one class of ubiquitous and highly important heterocycles, i.e. benzofurans, were synthesized with broad functional group compatibility. Furthermore, intermolecular condensations were also briefly investigated.
Asymmetric induction during electron transfer mediated photoreduction of carbonyl compounds: Role of zeolites
Shailaja,Kaanumalle, Lakshmi S.,Sivasubramanian, Karthikeyan,Natarajan, Arunkumar,Ponchot, Keith J.,Pradhan, Ajit,Ramamurthy
, p. 1561 - 1571 (2008/02/03)
Photochemistry of 17 aryl alkyl ketones included within cation exchanged zeolites has been examined. In solution five of the 17 ketones undergo intramolecular hydrogen abstraction reaction even in the presence of a chiral amine and the rest are photoreduced to the corresponding alcohol. Within zeolites all 17 ketones yielded in presence of a chiral amine, the corresponding alcohol as the major product. When a chiral amine was used as the coadsorbent within alkali ion exchanged zeolites, enantiomerically enriched alcohol was formed in all cases. The best chiral induction was obtained with phenyl cyclohexyl ketone (enantiomeric excess: 68%). 1H-13C Cross Polarization Magic Angle Spinning (CP-MAS) experiments, with a model ketone (perdeuterated acetophenone) and chiral amine (pseudoephedrine) included within MY zeolites, suggested that the cation brings the reactant and the chiral amine closer. The role of the cation in such a process is also revealed by the computation results. The results presented here highlight the importance of a supramolecular structure in forcing a closer interaction between a reactant and a chiral inductor that could be used to achieve asymmetric induction in photoproducts. The Royal Society of Chemistry 2006.
Photocyclization Reactions. Part 5 [1]. Synthesis of Dihydrobenzofuranols Using Photocyclization of 2-Alkoxybenzophenones and Ethyl 2-Benzoylphenoxyacetates
Sharshira, Essam Mohamed,Shimada, Satoru,Okamura, Mutsuo,Hasegawa, Eietsu,Horaguchi, Takaaki
, p. 1797 - 1805 (2007/10/03)
Photocyclization reactions were carried out on 2-alkoxybenzophenones 1a-h and ethyl 2-benzoylphenoxyacetates 2a-e in acetonitrile. Irradiation of 1a-h gave dihydrobenzofuranols 4a-h in 68-84% yields. Similarly, irradiation of 2a-e afforded dihydrobenzofuranols 8a-e in 72-75% yields. Ethyl acrylates 9b-c were also produced in 6-8% yields from photoreactions of 2b-c. Substituent effects on cyclization of 1,5-biradical intermediates and reaction pathways are discussed. Benzophenones are useful compounds to prepare dihydrobenzofuranols by photocyclization.
Generation and Reactions of 2-Alkoxydiphenylcarbenes in Fluid Solution and Rigid Matrices
Tomioka, Hideo,Nakanishi, Keisaku,Izawa, Yasuji
, p. 465 - 470 (2007/10/02)
Irradiation of 2-alkoxydiphenyldiazomethanes 1 in cyclohexane at room temperature produced 3-phenyldihydrobenzofurans 3 presumably as a result of intramolecular C-H insertion of 2-alkoxydiphenylcarbenes 2.Irradiation of compounds 1 in cyclohexane matrix at -196 deg C gave intermolecular C-H insertion products 4 at the expense of benzofurans 3.The formation of products 4 is explicable in terms of H-atom tunnelling to the triplet state of carbenes 2, followed by coupling of the resulting radical pairs.Product ratios 3:4 were somewhat sensitive to the bulk of the alkoxy group at the 2-position.This can be explained in terms of the matrix effect on the relative population of the rotational isomers of the carbene 2.Irradiation of compounds 1 in methanol at room temperature afforded O-H insertion products 5 almost exclusively, whereas irradiation in methanol matrix at -196 deg C gave C-H insertion products 6 along with other products 3 and 5.
The photocyclization of o-alkoxy phenyl ketones
Wagner, Peter J.,Meador, Michael A.,Park, Bong-Ser
, p. 5199 - 5211 (2007/10/02)
Several o-alkoxybenzophenones and o-(benzyloxy)benzophenones and -acetophenones photocyclize to 3-hydroxy-2,3-dihydrobenzofurans. Quantum yields generally are quite high, except for o-(benzyloxy)acetophenone. The o-ethoxy and o-benzyloxy ketones form two diastereomeric products, the Z isomer being highly preferred in hydrocarbon solvents, the E isomer being formed in comparable yield in methanol or with added pyridine. The reaction involves δ-hydrogen abstraction by the ketone triplets followed by cyclization of the 1,5-biradical intermediates. The biradicals have such short lifetimes that they usually cannot be detected by flash spectroscopy or trapped by thiols. Triplet state lifetimes, determined both by steady-state quenching studies and by flash kinetics, reveal that hydrogen abstraction rate constants are quite low. Arrhenius plots for triplet decay indicate activation energies of 3-5 kcal/mol and A values of 109 for the δ-hydrogen abstraction. MMX calculations and spectroscopic data all indicate that the ketones exist primarily in conformations with the carbon α to the ether oxygen twisted well away from the carbonyl. The low observed rate constants are ascribed to even lower equilibrium populations of conformers in the geometry required for reaction in the triplet state than in the ground state. 2,6-Diacylphenyl ethers show ten times the triplet reactivity of their monoacyl equivalents. In these cases, the ether function is twisted 90° such that the target C-H bond is much closer to a carbonyl. The large solvent effects on the stereochemistry of cyclization despite short biradical lifetimes suggest that bond rotations may induce intersystem crossing of the triplet biradicals. The low cyclization quantum yield from o-(benzyloxy)acetophenone and the formation of o-benzoylacetophenone as a major side product suggest that the 1,5-biradicals partially cyclize into the benzene ring to generate spiroenol intermediates. Rate constants for quenching of the triplet ketones by 2,5-dimethyl-2,4-hexadiene were measured. The kq values are ≥5 × 109 M-1 s-1 for the o-methoxy ketones but only 1-3 × 109 for the o-benzyloxy ketones. This rare steric effect on triplet energy transfer is attributed to twisting of the benzoyl chromophores caused by steric congestion.
