N-Heterocyclic carbenes as ligands in palladium-catalyzed Tsuji–Trost allylic substitution
作者:Yoshihiro Sato、Taro Yoshino、Miwako Mori
DOI:10.1016/j.jorganchem.2005.07.043
日期:2005.12
reaction. Allylicsubstitutionusing a Pd–NHC complex differed from that using a Pd–phosphine complex as follows: (1) the reaction using a Pd–NHC complex required elevated temperature (50 °C or reflux in THF), (2) allylic carbonates were inert to a Pd–NHC complex, and (3) nitrogen nucleophiles such as sulfonamide and amine did not react with allylic acetate. It was also found that allylicsubstitution with
研究了使用N-杂环卡宾作为配体的Pd(0)催化的烯丙基取代(即Tsuji-Trost反应)。业已证明,在咪唑-2-亚烷基骨架中的氮原子上带有庞大的芳香环的咪唑鎓盐2d适合用作配体前体,并且Pd 2 dba 3-咪唑鎓盐2d -Cs 2 CO 3该系统对于在该反应中生产Pd-NHC催化剂非常有效。使用Pd-NHC络合物的烯丙基取代与使用Pd-膦络合物的烯丙基取代具有以下区别:(1)使用Pd-NHC络合物的反应需要升高的温度(50°C或在THF中回流),(2)烯丙基碳酸酯对Pd-NHC络合物呈惰性,并且(3)氮亲核试剂(如磺酰胺和胺)不会与乙酸烯丙酯反应。还发现使用Pd-NHC催化剂用软亲核试剂进行烯丙基取代是通过整体保留构型而进行的,从而以立体特异性方式得到产物,立体化学反应过程显然与使用Pd-膦的反应相同。复杂的。
Preparation of five- and six- membered cyclic ketones by the palladium-catalyzed cyclization reaction. Application to methyl dihydrojasmonate synthesis
Methyl 3-oxo-8-phenoxy-6-octenoate (1) was cyclized using Pd(OAc)2-PPh3 as a catalyst to give 2-carbomethoxy-3-vinylcyclopentanone (2) and 2-carbomethoxy-4-cycloheptenone (3). The former was the main product in acetonitrile. 2-Alkylated 3-oxo-8-phenoxy-6-octenoates were converted mainly to the five-membered ketones. Based on this cyclization method, methyl dihydrojasmonate (8) was prepared from methyl
the highly oxygenated bicyclo[3.2.1]octane ring system through Mn(OAc)3‐mediated radical cyclization of alkynyl ketones was developed, which opens up a new avenue for the totalsynthesis of a number of highly oxidized diterpenoids. Application of this method enabled the first totalsynthesis of (−)‐glaucocalyxin A. Other salient features of the synthesis include a highly enantioselective conjugate
Optically active methyl (R)-3-oxo-7-(methoxycarbonyloxy)-8-nonenoate (1) underwent intramolecular allylation catalyzed by Pd(OAc)2-dppe in THF at room temperature to give racemic 3-vinyl-2-methoxycarbonylcyclohexanone (3), whereas similar palladium-catalyzed cyclization of a sodium salt of 1 proceeded very rapidly at 0 °C to form optically active 3, indicative of complete retention of the original chiral center.