The reaction of α-nitro ketones to the corresponding α-hydroxy ketones under basic aqueous conditions, a novel transformation, was studied. The investigation revealed that the reaction is only possible with α-nitro ketones that are CH-acidic in the α′-position and readily deprotonated under the reaction conditions. The NO2/OH exchange was established to proceed with retention of configuration at the
Acid-catalyzed reaction of β,β′-disubstituted cross conjugated dienones or the corresponding ethylene acetals gives mainly 2,3-disubstituted 2-cyclopentenones in stead of the simple Nazarov cyclization products, 3,4-disubstituted 2-cyclopentenones. This transformation is explained in terms of electrocyclic ring-closure, addition of hydroxylic solvent(s), tautomerization of the resulting 2-hydroxycyclopentanone
Homochiral ketals in organic synthesis. Diastereoselective cyclopropanation of α,β-unsaturated ketals derived from 1,4-D1-O-benzyl-l-threitol
作者:Eugene A. Mash、Keith A. Nelson
DOI:10.1016/s0040-4020(01)90002-x
日期:——
2-Cycloalken-1-one 1,4-di --benzyl -L-threitol ketals undergo efficient and diastereoselective cyclopropanation when treated with an excess of the Simmons-Smith reagent. For example, 2-cyclohexen-1-one 1,4-di --benzyl -L-threitol ketal gave in 90-98% yield a 9:1 mixture of diastereomeric cyclopropanes as established by 62.9 MHz 13C NMR spectroscopy and by hydrolysis of the mixture to (1,6)-bicyclo[4
当用过量的Simmons-Smith试剂处理时,2-Cycloalken-1-one 1,4-二--苄基-L-苏糖醇缩酮会发生高效且非对映选择性的环丙烷化。例如,由62.9 MHz 13 C NMR光谱法和水解确定,2-环己烯-1-酮1,4-二-苄基-L-苏糖醇缩酮的收率为90-98%,为非对映体环丙烷的9:1混合物将混合物制成(1,6 )-双环[4.1.0]庚烷-2-酮。给出了十六个其他实例,这些实例证明了2-环烯-1-酮缩酮的制备方法的一般性和可预测性,因为不幸的是,它对α,β-不饱和1,4-二-苄基-L-苏糖醇缺乏非对映选择性乙缩醛。
Palladium-Catalyzed Carbonylative Cyclization of Unsaturated Aryl Iodides and Dienyl Triflates, Iodides, and Bromides to Indanones and 2-Cyclopentenones
作者:Steve V. Gagnier、Richard C. Larock
DOI:10.1021/ja0212009
日期:2003.4.1
carbonylative cyclization is particularly effective on substrates that contain a terminal olefin. The proposed mechanism for this annulation includes (1) Pd(OAc)(2) reduction to the active palladium(0) catalyst, (2) oxidative addition of the organichalide or triflate to Pd(0), (3) coordination and insertion of carbon monoxide to produce an acylpalladium intermediate, (4) acylpalladation of the neighboring
Treatment of (3,3-dialkyl-2,2-dichlorocyclopropyl)methanols with hydrobromic acid gives 2-cyclopentenones through postulated intermediates, 3-chlorocyclopentadienyl cations. Another method which sh...