- Electrooxidative Cleavage of Carbon-Carbon Linkages. 1. Preparation of Acylic Oxoalkanoates from 2-Hydroxy- and 2-Acetoxy-1-cycloalkanones and Cycloalkanone Enol Acetates
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A methodology is described for the synthesis of acyclic oxoalkanoates 2 by electrooxidative cleavage of carbon-carbon linkages of 2-oxocycloalkan-1-ols 1 and cycloalkanone enol acetates 3.The electrolysis of 1 was carried out in a MeOH-LiClO4-(Pt) system at a constant applied voltage of 20 V by using a divided cell, giving 2 in 82-97 percent yields.On the other hand, 3 was electrolyzed in MeOH-AcOH (10:1)-LiClO4-(Pt) at 2-8 deg to give 2 in 72-79 percent yields.Electrolysis of 4-hydroxy-p-menth-8-ene afforded methyl (3R)-3,7-dimethyl-6-oxo-7-octenoate, a chiral synthetic block for the synthesis of (+)-rose oxide, in 84 percent yield.Similarly, the procedure could be applied to the preparation of methyl(+)-6-oxo-6,7-dihydrocitronellate from (+)-menthone enol acetate (74 percent) as well as 4-hydroxy-p-menthone (94 percent).Other lithium salts, i.e., LiBF4 and CF3CO2Li, can be used for the present purpose, but there are some difficulties in producing 2 with Et4NOTs and Et4NClO4.A plausible mechanism of the formation of 2 from 1 is also discussed.
- Torii, Sigeru,Inokuchi, Tsutomu,Oi, Ryu
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- α-Nitro Ketones. 6. Synthesis and Conformation of 2-Methyl-2-nitro-, cis- and trans-6-Methyl-2-nitro-, and cis- and trans-2,6-Dimethyl-2-nitrocyclohexanones
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Nitration of the most substituted (thermodynamically more stable) enol acetate or trimethylsilyl ether of 2-methylcyclohexanone and the phase-transfer methylation of 2-nitrocyclohexanone serve as methods of preparation of 2-methyl-2-nitrocyclohexanone, whereas nitration of the least substituted enol acetate or trimethylsilyl ether of 2-methylcyclohexanone and methylation of the dianion of 2-nitrocyclohexanone lead to cis- and trans-6-methyl-2-nitrocyclohexanone.Nitration of the enol acetate or trimethylsilyl ether of 2,6-dimethylcyclohexanone and methylation of either2-methyl-2-nitro- or 6-methyl-2-nitrocyclohexanone are methods of preparation of cis- and trans-2,6-dimethyl-2-nitrocyclohexanone. 1H NMR chemical shift and coupling constant data were used to determine the preferred conformations of the cyclohexanones: 2(e)-methyl-2(a)-nitro, cis-6(e)-methyl-2(e)-nitro, trans-6(e)-methyl-2(a)-nitro, cis-2(e),6(e)-dimethyl-2(a)-nitro, trans-2(a)-methyl-6(e)-methyl-2(e)-nitro.
- Dampawan, Pimchit,Zajac, Walter W.
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p. 1176 - 1181
(2007/10/02)
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