Decarboxylative (4+1) Oxidative Annulation of Malonate Monoesters with 2‐Vinylpyridine Derivatives

A novel N‐iodosuccinimide‐mediated decarboxylative (4+1) oxidative annulation between 2‐vinylpyridine derivatives and malonate monoesters was developed. It offers a new way to construct indolizine derivatives by utilizing malonate monoesters as a C₁ unit. The alkyl 2,2‐diiodoacetate was found to be the active reaction intermediate during the transformation.

     

8-位取代嘌呤衍生物的合成与机理研究

以9 -苄基嘌呤和碘代丁二酰亚胺(NIS)为原料,研究开发了8 碘9 -苄基嘌呤合成的新方法。较佳反应条件为:反应溶剂THF,反应温度70 ℃,n(9 苄基嘌呤)∶n(NIS)=1∶2.5,反应时间48 h。在此条件下,产品收率达87%以上。另外,以(Ph3P)2PdCl2为催化剂,对8 碘9 苄基嘌呤与有机基锡试剂RSnBu3 之间的Stille 偶合反应进行了研究。得到较佳反应条件为:反应温度80~100 ℃,n(8 碘9 苄基嘌呤)∶n(RSnBu3)∶n((Ph3P)2PdCl2)= 1 0∶1 2∶0.05,反应时间24 h。在上述条件下,产品收率为91%(R=乙烯基)、86%(R=2 噻吩基)、90%(R=2 呋喃基)、80%(R=苯乙炔基)和42%(R=苯基)。采用1 H NMR、13 C NMR、MS、碳氢相关谱(HETCOR)和远程碳氢相关谱(Long Range HETCOR)等分析手段对所得产物结构进行了表征,证明其结构正确,并对两步反应的机理进行了探讨。     

Direct Metal-Free Transformation of Alkynes to Nitriles: Computational Evidence for the Precise Reaction Mechanism

Density functional theory calculations elucidated the precise reaction mechanism for the conversion of diphenylacetylenes into benzonitriles involving the cleavage of the triple C≡C bond, with N-iodosuccinimide (NIS) as an oxidant and trimethylsilyl azide (TMSN₃) as a nitrogen donor. The reaction requires six steps with the activation barrier ΔG^‡ = 33.5 kcal mol⁻¹ and a highly exergonic reaction free-energy ΔG_R = −191.9 kcal mol⁻¹ in MeCN. Reaction profiles agree with several experimental observations, offering evidence for the formation of molecular I₂, interpreting the necessity to increase the temperature to finalize the reaction, and revealing thermodynamic aspects allowing higher yields for alkynes with para-electron-donating groups. In addition, the proposed mechanism indicates usefulness of this concept for both internal and terminal alkynes, eliminates the option to replace NIS by its Cl- or Br-analogues, and strongly promotes NaN₃ as an alternative to TMSN₃. Lastly, our results advise increasing the solvent polarity as another route to advance this metal-free strategy towards more efficient processes.     

8-碘-9-苄基-9H-嘌呤的合成

以9 苄基 9H 嘌呤和碘代丁二酰亚胺(NIS)等为主要原料,以THF为溶剂,对8 碘 9 苄基 9H 嘌呤的合成反应进行了研究。对主要反应条件的影响结果进行了考察,在反应温度70℃,n(9 苄基 9H 嘌呤)∶n(碘代丁二酰亚胺)=1 0∶2 5,反应时间48h的较佳条件下,产物收率>87%。用1HNMR、13CNMR、MS、碳氢相关谱(HETCOR)和远程碳氢相关谱(LongRangeHETCOR)等技术对产物结构进行了表征。