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

• easily available, which have been established as versatile synthetic building blocks for the synthesis of cyclic scaffolds [25]. In 2016, Zhu et al. reported the first example of a Rh-catalyzed C–H functionalization of enaminones with alkynes and α-diazo-β-ketoesters to access naphthalenes [26]. Very

Enantioselective carbenoid insertion into C(sp³)–H bonds

• J. V. Santiago and
• A. H. L. Machado

Beilstein J. Org. Chem. 2016, 12, 882–902, doi:10.3762/bjoc.12.87

• in the catalytic cycle of this transformation. From the 1990s, the enantioselective carbenoid insertion into C(sp3)–H bonds starts to be better discussed in the literature. Ikegami and coworkers reported the enantioselective insertion of α-diazo-β-ketoesters into C(sp3)–H bonds catalyzed by rhodium

• porphyrin-based catalyst for enantioselective carbenoid insertion into C(sp3)–H bond. Rhodium porphyrin-based catalyst for enantioselective carbenoid insertion into benzylic C(sp3)–H bond. Enantioselective insertion of α-diazo-β-ketoesters into C(sp3)–H bonds catalyzed by chiral rhodium(II) complexes 17a

Azirinium ylides from α-diazoketones and 2H-azirines on the route to 2H-1,4-oxazines: three-membered ring opening vs 1,5-cyclization

• Nikolai V. Rostovskii,
• Mikhail S. Novikov,
• Alexander F. Khlebnikov,
• Galina L. Starova and
• Margarita S. Avdontseva

Beilstein J. Org. Chem. 2015, 11, 302–312, doi:10.3762/bjoc.11.35

• , rhodium carbenoids derived from α-diazocarbonyl compounds transform 2H-azirines 1 to azirinium ylides 5 (Scheme 1) which undergo facile N–C2 bond cleavage to give 2-azabuta-1,3-dienes 3. Recently we showed that the use of α-diazo-β-ketoesters 2 in these reactions, which are finished by 1,6-cyclization of

• cyclize into oxazine 4a under the reaction conditions. According to our previous computational and experimental results for transformations of 3,4-diphenyl-substituted 2-azabuta-1,3-dienes derived from α-diazo-β-ketoesters, oxazine 4a formed via rapid cyclization of azadiene E-3a [15], whereas 2-azabuta

• rearrangement into a ketene derivative. To obtain experimental evidence for the formation of azirenooxazole intermediates 10 in the reactions of azirines 1 with α-diazo-β-ketoesters, we reacted azirine 1g with a mixture of two diazo compounds, ethyl diazoacetoacetate (2d) and diazoacetylacetone (2c), in the

Intramolecular carbenoid ylide forming reactions of 2-diazo-3-keto-4-phthalimidocarboxylic esters derived from methionine and cysteine

• Marc Enßle,
• Stefan Buck,
• Roland Werz and
• Gerhard Maas

Beilstein J. Org. Chem. 2012, 8, 433–440, doi:10.3762/bjoc.8.49

• reaction. Keywords: α-aminoacids; carbonyl ylides; cycloaddition; α-diazo-β-ketoesters; sulfonium ylides; Introduction The synthetic potential of diazo compounds, in particular of α-diazoketones and α-diazoesters, is greatly widened by the ability of the derived carbene or metal-carbene intermediates to

• , yielding either a cyclic sulfonium ylide or a six-ring carbonyl ylide. In fact, it has been found that Rh(II)-catalyzed dediazoniation of α-diazo-β-ketoesters with γ-phthalimido [18][19] or related [20] substituents gives rise to cyclic carbonyl ylides, which were trapped by intermolecular cycloaddition

• reactions. In this paper, we report that the formation of sulfonium as well as carbonyl ylides are indeed competing pathways in the Rh(II)-catalyzed dediazoniation of phthaloyl-protected γ-amino-α-diazo-β-ketoesters derived from methionine, S-benzylcysteine, and S-allylcysteine. Results and Discussion