Enantioselective addition of β-functionalized allylboronates to aldehydes and aldimines. Stereocontrolled synthesis of α-methylene-γ-lactones and lactams
We report results regarding the development of condensations of chiral β-alkoxycarbonylallylboronates on aldehydes and imines. These allylboronates add in a highly enantioselective and diastereospecific manner to afford biologically and synthetically useful chiral α-methylene-γ-butyrolactones and lactams. The nature of the electrophile (aldehyde vs imine) is shown to have a dramatic influence on the
Triflic Acid-Catalyzed Additions of 2-Alkoxycarbonyl Allylboronates to Aldehydes. Study of Scope and Mechanistic Investigation of the Reaction Stereochemistry
作者:Tim G. Elford、Yuichiro Arimura、Siu Hong Yu、Dennis G. Hall
DOI:10.1021/jo062151b
日期:2007.2.1
The substrate scope and the effect of substrate on the observed inversion of stereoselectivity in the triflic acid-catalyzed allylboration reaction between 2-alkoxycarbonyl allylboronates and aldehydes are presented. A mechanisticinvestigation is described so as to confirm the involvement of a carbocation intermediate as the source of stereochemical inversion. This methodology allows a facile access
The asymmetric synthesis of α-methylene-γ-butyrolactones via a tandem allylboration/lactonization approach was achieved using a chiral N,N′-dioxide/AlIII complex. The kinetic resolution of the allylboration intermediate via asymmetric lactonization was found to be a key aspect responsible for the success of this transformation. Stereodivergent syntheses and total syntheses of eupomatilones 2, 5 and
使用手性N , N ' -二氧化物/Al III络合物,通过串联烯丙基硼化/内酯化方法实现了 α-亚甲基-γ-丁内酯的不对称合成。发现烯丙基硼化中间体通过不对称内酯化的动力学拆分是该转化成功的关键因素。对Eupomatilones 2、5和6的立体发散合成和全合成证明了其合成实用性。
Novel Functionalized Trisubstituted Allylboronates via Hosomi−Miyaura Borylation of Functionalized Allyl Acetates
A series of novel functionalized achiral and chiral allylboronates have been synthesized via the nucleophilic addition of boronates on allyl acetates derived via vinylalumination or Baylis-Hillman reaction of aldehydes. These reagents, upon allylboration with aldehydes, furnish,beta-substituted-alpha-methylene-gamma-butyrolactones stereoselectively.
Total Synthesis of the Eupomatilones
作者:Soumya Mitra、Srinivas Reddy Gurrala、Robert S. Coleman
DOI:10.1021/jo701415m
日期:2007.11.1
Full details of the total syntheses of five members of the eupomatilone family of lignans are reported.