The photoamination of 1-arylalka-1,3-dienes 1a–f and
1-aryl-4-phenylbuta-1,3-dienes 1g–k with NH3 in the
presence of p-dicyanobenzene (DCB) gives 4-amino-1-arylalk-2-enes
2a–f and 1-amino-1,4-diarylbut-2-enes 2g–k, respectively. The
photoamination proceeds by nucleophilic addition of NH3 to the
cation radicals of 1+˙ generated by photoinduced
electron transfer to DCB. The regiochemistry of 2 is related to the
distribution of the positive charge in 1+˙ calculated
by the PM3-UHF/RHF method, the stability of the aminated radicals formed by
the addition of NH3 to 1+˙ and the
stability of the aminated anion formed by the reduction of the aminated
radicals by DCB-˙. The stabilities of these
intermediates are estimated by the calculation of the heat of formation by
the PM3-UHF/RHF method. Distributions of the positive charge in
1+˙ and the stabilities of the aminated anion show a
good agreement with the product analysis.
Bioinspired Diastereoconvergent Synthesis of the Tricyclic Core of Palodesangrens via Diels–Alder Reaction, LiAlH<sub>4</sub>-Mediated Isomerization, and Acid-Mediated Cyclization
electron-deficient chalcones as the dienophile. During the reduction of ketone to the corresponding alcohol by LiAlH4, the mixture of endo and exo isomers underwent a novel diastereoconvergent LiAlH4-mediated isomerization to install the desired stereochemistry at C10a. Subsequent pyran ring closure under acidic conditions installed the stereochemistry at the remaining C6. Overall, the tricyclic core of palodesangrens
的环己烯部分的三环6,7-二芳基四氢-6- ħ -苯并[ c ^ ] palodesangrens的色烯核心可在仿生和步骤-经济的方式由所述富电子(之间的Diels-Alder反应来组装ë) -1,3-丁二烯芳烃为二烯,缺电子查耳酮为亲二烯体。在LiAlH 4将酮还原为相应的醇的过程中,内和外异构体的混合物经历了一种新的非对映收敛的LiAlH 4。-介导的异构化以在C10a处安装所需的立体化学。随后在酸性条件下的吡喃环闭合将立体化学安装在剩余的C6上。总体而言,可以分三步制备palodesangrens的三环核,产率最高可达38%。
Cu-catalyzed regioselective borylcyanation of 1,3-dienes
作者:Lu Wen、Haiyan Zhang、Jiping Wang、Fanke Meng
DOI:10.1039/c8cc07032f
日期:——
Catalytic regioselective generation of an allyl–Cu complex through Cu–B(pin) (pin = pinacolato) addition to 1,3-dienes followed by reaction with an electrophilic cyanation reagent to afford multifunctional organoboron compounds is presented. Reactions of a wide range of 1,3-dienes with different substitution patterns promoted by an easily accessible phosphine–Cu complex proceed with high yields and
precatalyst and tBuNH2 as the cocatalyst. This catalyst system provides an efficient and atom-economical access to unsymmetrical (E,E)-1,4-diarylbutadienes with high yields and stereoselectivities. Monitoring the process revealed that a sequence of cis-semihydrogenation of the triple bond of 1,3-enynes (to form (E,Z)-butadienes) and (E,Z)-to-(E,E) isomerization occurs to form (E,E)-butadienes.
使用新的 (PCN)Ir 配合物作为预催化剂和t BuNH 2作为助催化剂,开发了以乙醇为氢源的 1,3-烯炔的反式半氢化反应。该催化剂体系以高产率和立体选择性提供了一种高效且原子经济地获得不对称 ( E , E )-1,4-二芳基丁二烯的途径。监测过程显示,1,3-烯炔的三键顺式半氢化(形成 ( E , Z )-丁二烯)和 ( E , Z ) 到-( E , E ) 异构化形成( , _E )-丁二烯。