Synthesis of Tetrahydrofurans by a Tandem Hydrogen Atom Abstraction/Radical Nucleophilic Displacement Sequence
摘要:
The reaction of a series of 5-(N-phthalimidoxy)-1-phenyl-1-(diphenylphosphatoxy)pentanes with triphenyltin hydride and AIBN provides alkoxy radicals which undergo 1,5-hydrogen atom abstraction to give beta-(phosphatoxy)alkyl radicals. These radicals then take part in a radical nucleophilic displacement leading, after chain transfer, to tetrahydrofurans.
epoxidation of α-cyclopropylidene alcohols). The isomerisation, either spontaneous or through reaction with lithium halides, of oxaspiropentyl ketones and acetals, gives 2-acyl-cyclobutanones and corresponding mono-acetals. These new unstable 1,3-diones nust be stored in CCl4 solution. They are present in the dione form only. They add water and methanol, in acidic and even in neutral medium, leading to ring
Oxaspiropentyl ketones and acetals prepared from α-cyclopropylidene ketones and acetals undergo, with lithium halides, isomerisation to 2-acylcyclobutanones and monoacetals.
Iodine(III)-Mediated Contraction of 3,4-Dihydropyranones: Access to Polysubstituted γ-Butyrolactones
作者:Robin Dagenais、Tommy Lussier、Claude Y. Legault
DOI:10.1021/acs.orglett.9b01893
日期:2019.7.5
underappreciated strategy to access these compounds. To the best of our knowledge, very few examples of this strategy have been reported, with limited investigation of the influence of stereogenic centers on the starting dihydropyranones. We investigated the iodine(III)-mediated contraction of a representative set of dihydropyranone derivatives. The method gives rapid access to functionalized γ-butyrolactones
Michael Addition of Stannyl Ketone Enolate to α,β-Unsaturated Esters Catalyzed by Tetrabutylammonium Bromide and an ab Initio Theoretical Study of the Reaction Course
作者:Makoto Yasuda、Kouji Chiba、Noriyuki Ohigashi、Yasuhiro Katoh、Akio Baba
DOI:10.1021/ja028853+
日期:2003.6.1
Michael addition of stannyl ketone enolates to alpha,beta-unsaturated esters was accomplished in the presence of a catalytic amount of tetrabutylammonium bromide (Bu(4)NBr). Other typical systems using lithium enolate or silyl enolate with catalysts (TiCl(4) or Bu(4)NF) failed to give the desired products. The bromide anion from Bu(4)NBr coordinates to the tin center in enolate to accelerate the conjugate
A strategically novel kinetic resolution of β-substituted olefiniccarboxylicacids is developed by asymmetric bromolactonization using an organocatalyst, 4-tBuPh-tris 1b. The cyclization stage, which provides δ-lactone, is proposed to be operative for discrimination of each enantiomer of carboxylicacids.
通过使用有机催化剂4 - t BuPh-tris 1b进行不对称溴分子内酯化,开发出了具有战略意义的新型β-取代烯烃羧酸动力学拆分方法。提出提供δ-内酯的环化阶段可用于区分羧酸的每种对映体。