Expedient Synthesis of Fused Azepine Derivatives Using a Sequential Rhodium(II)-Catalyzed Cyclopropanation/1-Aza-Cope Rearrangement of Dienyltriazoles
作者:Erica E. Schultz、Vincent N. G. Lindsay、Richmond Sarpong
DOI:10.1002/anie.201405356
日期:2014.9.8
reported. The process involves an intramolecular cyclopropanation of an α‐imino rhodium(II) carbenoid, leading to a transient 1‐imino‐2‐vinylcyclopropane intermediate which rapidly undergoes a 1‐aza‐Coperearrangement to generate fused dihydroazepine derivatives in moderate to excellent yields. The reaction proceeds with similar efficiency on gram scale. The use of catalyst‐free conditions leads to the formation
报道了一种从带有系链二烯的 1-磺酰基-1,2,3-三唑形成稠合二氢氮杂卓衍生物的一般方法。该过程涉及 α-亚氨基铑 (II) 类卡宾的分子内环丙烷化,产生短暂的 1-亚氨基-2-乙烯基环丙烷中间体,该中间体迅速发生 1-氮杂-Cope 重排,以中等至优异的产率生成稠合二氢氮杂卓衍生物。该反应在克规模上以类似的效率进行。使用无催化剂条件导致形成新的 [4.4.0] 双环杂环。
Regioselective Control in the Palladium-Catalyzed Isomerization of Methylenecyclopropylcarbinols Using Acetic Acid as a Reagent
作者:Min Shi、Bao-Yu Wang、Li-Xiong Shao
DOI:10.1055/s-2007-973871
日期:2007.4
Tuning the regioselectivity of the Pd-catalyzed isomerization of methylenecyclopropylcarbinols in acetic acid is achieved by a subtle choice of the ligand and/or solvent. When dioxane is used as the solvent, penta-2,4-dien-1-ols are formed, whereas when AsPh 3 is used as the ligand and toluene is used as the solvent, pent-4-enals are formed. A plausible reaction mechanism is discussed on the basis
remote functionalizations based on alkene isomerization. In contrast, protocols based on alkyne isomerization are comparatively rare. Herein, we report a general Pd-catalyzed long-range isomerization of alkynyl alcohols. Starting from aryl-, heteroaryl-, or alkyl-substituted precursors, the optimized system provides access preferentially to the thermodynamically more stable α,β-unsaturated aldehydes
Phenyl acetates were selectively obtained in good yields by cyclocarbonylation of 2,4-pentadienyl acetates in the presence of NEt3, Ac2O, and a catalytic amount of palladium complexes such as PdCl2(PPh3)2 at 120-140-degrees-C under 50 atm of CO. No five-membered ring products were observed. A platinum complex PtCl2(PPh3)2 was also effective as a catalyst. The reaction of 5-phenyl-2,4-pentadienyl bromide with M(CO)(PPh3)3 (M = Pd or Pt) under CO gave the corresponding 6-phenyl-3, 5-hexadienoyl complexes in a high yield, which in turn afforded 2-acetoxybiphenyl in 41-51% yield on heating to 160-degrees-C under 50 atm of CO in the presence of NEt3 and Ac2O. Similar 3,5-hexadienoyl complexes are proposed to be intermediates in the catalytic cyclocarbonylation of 2,4-pentadienyl acetates. On the other hand, PdCl2(PPh3)2-catalyzed carbonylation of o-(bromomethyl)(1-alkenyl)-benzenes in the presence of NEt3 and Ac2O gave 2-naphthyl acetates in moderate yields, while the reaction in the absence of Ac2O gave five-membered ring products such as 2-indanones or a tricyclic lactone by incorporation of one or two CO molecules, respectively.