- ε-Caprolactone manufacture via efficient coupling Baeyer-Villiger oxidation with aerobic oxidation of alcohols
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To avoid the use of peracids oxidant or highly concentrated hydrogen peroxide which is potentially hazardous and explosive, herein, a new route to ε-caprolactone was developed in which molecule oxygen was employed as the terminal oxidant. The commercial available N-hydroxyphthalimide and ammonium cerium nitrate were used as the key catalysts for the increased yield of ε-caprolactone. For instance, the selectivity of ε-caprolactone was obtained 92 % with 85 % conversion of cyclohexanone which was comparable to the strategies using highly concentrated hydrogen peroxide. The sacrificed alcohols were transformed into corresponding ketones which were also valuable chemicals. Furthermore, the efficiency of the alcohols was achieved to unprecedented 52 %. The Baeyer-Villiger oxidation of various other cycloalkanones was also examined. The substituent group effect on the efficiency of sacrificed alcohols was investigated in which weak electron-donating substituent induced nearly quantitative yield of ε-caprolactone. The reaction mechanism was studied with the help of electron paramagnetic resonance which indicated the existence of a radical pathway.
- Du, Renfeng,Li, Haoran,Wang, Yongtao,Yao, Jia,Yuan, Haoran,Zhao, Chenxuan
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- Conjugate Addition Reactions Mediated by Samarium(II) Iodide
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Samarium(II) iodide in conjunction with a catalytic low-valent transition metal species has been employed to promote the conjugate addition reaction of primary and secondary alkyl halides onto α,β-unsaturated esters and amides. The method has been determined to be quite general and hence has been extended to the cyclization reactions of alkyl halides onto α,β-unsaturated lactones, lactams, and nitriles. The cyclization reactions described herein provide a very general approach to the synthesis of functionalized carbocycles from simple acyclic precursors with excellent diastereoselectivity and under very mild reaction conditions.
- Molander, Gary A.,Harris, Christina R.
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p. 7418 - 7429
(2007/10/03)
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- Acid-Catalyzed Hydrolysis of Bridged Bi- and Tricyclic Compounds. XXVI. The Mechanisms of Formation of the Hydration Products of 2-Norbornen-5-one
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The acid-catalyzed hydration of 2-norbornen-5-one (1) in 5 mol dm-3 HClO4 at 358 K produces, according to GLC analyses, exo-5-hydroxy-2-norbornanone (2), 2-oxabicycloctan-3-one (3), which is in equilibrium with cis-3-hydroxycyclopentaneacetic acid (5), and 2-oxabicyclooctan-3-one (4).The former lactone (3) is unstable and rearranges slowly to the latter (4).The ketoalcohol (2) is formed via the slow protonation of norbornenone at C(3) and via subsequent hydration of the carbocation.The lactones are formed via complicated routes started by the protonation of norbornenone at C(2), and comprising 3- and 2-cyclopentaneacetic acid (7 and 9) as unstable intermediate products.
- Lajunen, Martti,Lahti, Marjo,Heimo, Satu
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p. 771 - 776
(2007/10/02)
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