Palladium-Catalyzed Hydroboration/Cyclization of 1,<i>n</i>-Dienes
作者:Shota Kanno、Fumitoshi Kakiuchi、Takuya Kochi
DOI:10.1021/acs.joc.2c02781
日期:2023.2.17
While the hydroboration of alkenes is well established, the corresponding cyclization reaction of dienes remains challenging. Here, we report a new method for hydroboration/cyclization applicable to various 1,n-dienes and hydroboranes. The method features the direct synthesis of borylalkyl cyclopentanes from common 1,6-dienes, which is highlighted by syntheses of elaborated pyrrolidine cores from easily
虽然烯烃的硼氢化反应已经很成熟,但二烯的相应环化反应仍然具有挑战性。在这里,我们报告了一种适用于各种 1, n -二烯和氢硼烷的硼氢化/环化新方法。该方法的特点是从常见的 1,6-二烯直接合成硼烷基环戊烷,并通过从易于获得的二烯丙基胺合成精细的吡咯烷核来突出这一点。值得注意的是,1, n -二烯 ( n > 6) 也会形成五元环,提供“远程”硼氢化/环化,否则很难实现。
Cyclization/Hydrosilylation of Functionalized Dienes Catalyzed by a Cationic Palladium Phenanthroline Complex
作者:Ross A. Widenhoefer、Carmine N. Stengone
DOI:10.1021/jo9913006
日期:1999.11.1
Mixtures of(phen)PdMe2 (2a) and HBAr'(4) (3a) or (phen)PdMe(Cl) (2b) and NaBAr'(4) (3b) [phen = 1, 10-phenanthroline; Ar' = 3,5-C6H3(CF3)(2)] catalyzed the cyclization/hydrosilylation of functionalized 1,6-dienes to form silylated cyclopentanes in good yield and with excellent trans selectivity about the newly formed C-C bond (typically >50:1). A range of tertiary hydrosilanes were employed in the procedure although unhindered trialkylsilanes provided the most consistent results. The protocol tolerated a range of polar functionality including esters, ethers, amides, sulfones, and cyano groups. 4,4-Disubstitution on the diene backbone promoted cyclization, and a homoallylic ester, ketone, or ether directing group was required for efficient cyclization. The procedure tolerated dienes which possessed a single trans-substituted olefin and also tolerated allylic substitution. These substituted dienes underwent cyclization/hydrosilylation to form carbocycles resulting from transfer of the silyl group to the less hindered olefin. Mixtures of 2a and 3a also catalyzed the cyclization/hydrosilylation of functionalized 1,7-dienes to form silylated cyclohexane derivatives. Cyclization/hydrosilylation of 1,7-dienes was typically slower, less stereoselective, and more sensitive to substitution than was cyclization of 1,6-dienes.
Ibuka, Toshiro; Aoyagi, Takeshi; Yamamoto, Yoshinori, Chemical and pharmaceutical bulletin, 1986, vol. 34, # 6, p. 2417 - 2427