A convenient method for carbon extension of acetals and aldehydes has been established consisting of combining a ketenedithioacetal 1 and nucleophiles such as alkyl- and alkynylmetal, metal enolate, and hydride. Acetals and aldehydes react with 1 in the presence of TMSOTf, and the successive addition of nucleophiles affords the corresponding β-alkoxy and β-siloxy dithioacetals in good yields.
Aldehydes vs Aldimines. Unprecedented Aldimine-Selective Nucleophilic Additions in the Coexistence of Aldehydes Using a Lanthanide Salt as a Lewis Acid Catalyst
作者:Shū Kobayashi、Satoshi Nagayama
DOI:10.1021/ja971153y
日期:1997.10.1
It is well-recognized that aldimines are less reactive than aldehydes toward nucleophilic additions. In this paper, an unprecedented change in the reactivity is described: preferential reactions of aldimines over aldehydes in nucleophilic additions using a lanthanide salt as a Lewis acidcatalyst. In the presence of a catalytic amount of ytterbium triflate (Yb(OTf)3), only aldimines reacted with silyl
Highly Functionalized and Potent Antiviral Cyclopentane Derivatives Formed by a Tandem Process Consisting of Organometallic, Transition-Metal-Catalyzed, and Radical Reaction Steps
A simple modular tandem approach to multiply substituted cyclopentanederivatives is reported, which succeeds by joining organometallic addition, conjugateaddition, radical cyclization, and oxygenation steps. The key steps enabling this tandem process are the thus far rarely used isomerization of allylic alkoxides to enolates and single‐electron transfer to merge the organometallic step with the radical
A novel synthesis of functionalized 1,1-difluoro-1-alkenes via isolable 2,2-difluorovinylsilanes
作者:Junji Ichikawa、Yuichiro Ishibashi、Hiroki Fukui
DOI:10.1016/s0040-4039(02)02652-7
日期:2003.1
Various 1,1-difluoro-1-alkenes such as monosubstituted 1,1-difluoro-1-alkenes, 2-bromo-1,1-difluoro-1-alkenes, and 1,1-difluoro-3-hydroxy-1-alkenes are prepared in two simple steps from 1-trifluoromethylvinylsilane: (i) its SN2′ reaction with nucleophiles to construct 2,2-difluorovinylsilanes and (ii) the subsequent substitution of electrophiles for the vinylic silyl group.
各种1,1-二氟-1-烯烃,例如单取代的1,1-二氟-1-烯烃,2-溴-1,1-二氟-1-烯烃和1,1-二氟-3-羟基-1-从1-三氟甲基乙烯基硅烷通过两个简单的步骤制备烯烃:(i)S N 2'与亲核试剂的反应以构建2,2-二氟乙烯基硅烷,以及(ii)随后用亲电试剂取代乙烯基甲硅烷基。
Regioselective addition of titanium enolates to 1-acylpyridinium salts. A convenient synthesis of 4-(2-oxoalkyl)pyridines
作者:Daniel L. Comins、Jack D. Brown
DOI:10.1016/s0040-4039(01)81368-x
日期:1984.1
Titanium enolates add to the 4-position of 1-phenoxycarbonylpyridinium salts to give 1,4-dihydropyridines; subsequent aromatization provides 4-(2-oxoalkyl)pyridines.