Transition-metal-catalyzed domino reactions of strained bicyclic alkenes

• Austin Pounder,
• Eric Neufeld,
• Peter Myler and
• William Tam

Beilstein J. Org. Chem. 2023, 19, 487–540, doi:10.3762/bjoc.19.38

• exo face of 30b, oxidative cyclization can afford the ruthenacycle 101. Unlike previous works studying Ru-catalyzed cyclizations involving bicyclic alkenes and alkynes [56][57][58][59], the reaction preferentially undergoes β-hydride elimination to generate 102 rather than reductive elimination which

• state, followed by coordination to the alkyne generates intermediate 109. Migratory insertion of the alkyne results in the ruthenacycle 110. Subsequent reductive elimination generates putative allyl vinyl ether 111 and regenerates the active ruthenium complex. The allyl vinyl ether intermediate

Practical synthesis of isocoumarins via Rh(III)-catalyzed C–H activation/annulation cascade

• Qian-Ci Gao,
• Yi-Fei Li,
• Jun Xuan and
• Xiao-Qiang Hu

Beilstein J. Org. Chem. 2023, 19, 100–106, doi:10.3762/bjoc.19.10

• active Rh catalyst. Subsequently, the oxygen atom of the enaminone is coordinated to the Rh catalyst, following by a Rh(III)-promoted ortho C–H activation to form a five-membered ruthenacycle 1-A. Then, the reaction of the iodonium ylide with intermediate 1-A generates a Rh-carbenoid intermediate 1-B

When metal-catalyzed C–H functionalization meets visible-light photocatalysis

• Lucas Guillemard and
• Joanna Wencel-Delord

Beilstein J. Org. Chem. 2020, 16, 1754–1804, doi:10.3762/bjoc.16.147

• , ortho-C–H activation delivering the photoactive intermediate. Under visible-light irradiation, the SET process from the excited ruthenacycle to the haloalkane coupling partner leads to the formation of a stabilized alkyl radical (Figure 39). Next, radical attack at the para-position of the carbohydrate

Attempted synthesis of a meta-metalated calix[4]arene

• Christopher D. Jurisch and
• Gareth E. Arnott

Beilstein J. Org. Chem. 2019, 15, 1996–2002, doi:10.3762/bjoc.15.195

• yielding transformations to azide and 1,2,3-triazole derivatives which may have application in other areas of research. Keywords: calixarene; inherent chirality; mesoionic carbene; mononitration; ruthenacycle; Introduction Calix[4]arenes are a class of diverse macrocyclic compounds which have been the

• Ullmann-type coupling to give aryl azide 2, which readily reacted with phenylacetylene in a copper-catalyzed Huisgen 1,3-dipolar cycloaddition to give 1,2,3-triazole 3 (Scheme 1). The formation of the ruthenacycle was then achieved using Albrecht’s method involving regioselective methylation of triazole 3

• 5 in 44% yield which was comparable to the yields reported by Albrecht [20]. Synthesis of the calix[4]arene ruthenacycle Satisfied that the published methods worked in our hands, we then set about synthesizing the targeted mesoionic calix[4]arene ruthenacycle. Our first key intermediate was

Catalysis of linear alkene metathesis by Grubbs-type ruthenium alkylidene complexes containing hemilabile α,α-diphenyl-(monosubstituted-pyridin-2-yl)methanolato ligands

• Tegene T. Tole,
• Johan H. L. Jordaan and
• Hermanus C. M. Vosloo

Beilstein J. Org. Chem. 2019, 15, 194–209, doi:10.3762/bjoc.15.19

• ruthenacycle. In addition, the relatively low ruthenium metal positive charge on 9 would cause it to have a high initiation rate constant [19]. On the other hand, the 3-Me group in 6 will strengthen the Ru–N chelation via inductive electron-donation and steric repulsion between the methyl group and the two

• phenyl rings. As a result of the steric interaction 6 has a planar five-membered ruthenacycle geometry (Figure 9). In the absence of substituents on the pyridinyl moiety it is expected that the resulting precatalyst will be more active at lower temperatures. This is indeed the case when 5d is used as

• of 6, the Me group is in a crowded environment due to its proximity to the two α-phenyl groups, which upon opening the Ru–N chelation, would even become more sterically crowded. This results in a planar geometry of the five-membered ruthenacycle while 8 exhibits an envelope geometry. The Ru–N (2.179