trans-Cyclopropyl β-Amino Acid Derivatives via Asymmetric Cyclopropanation Using a (Salen)Ru(II) Catalyst

Abstract

trans-Cyclopropyl beta-amino acid derivatives can be synthesized in five steps with excellent enantioselectivities using a chiral (Salen)Ru(II) cyclopropanation catalyst in the key asymmetry-induction step. This facile synthesis proceeds with high overall yield and can be used to prepare a number of carbamate-protected (Cbz and Boc are demonstrated) beta-amino acid derivatives.

Recyclable Polymer‐ and Silica‐Supported Ruthenium(II)‐Salen Bis‐pyridine Catalysts for the Asymmetric Cyclopropanation of Olefins

“…97%) could be achieved for both polymer resin catalysts over the three cycles tested without any apparent deactivation ( Table 2, entries 1-6). Initial cycles gave similar results as shown in Table 1, and subsequent cycles showed marginally better selectivities (entries 1-2, [4][5]. This marginal increase may result from removal of any residual, non-chiral ruthenium species that may not have been removed during the filtration steps following the metallation procedure.…”

“…Recently, ruthenium-salen catalysts have been shown to demonstrate high activities and selectivities for the cyclopropanation of olefins (Scheme 1), while maintaining functional group tolerance for a range of electronically diverse olefins. [3,4] With advancements in homogeneous asymmetric cyclopropanation catalysis, several researchers have been working on the development of supported, single-sited heterogeneous catalysts in parallel. Immobilization of these catalysts on solid phase supports allows for the facile recovery and reuse of the asymmetric catalyst, which can be important for a variety of economic, environmental, and quality control reasons.…”

Construction of All‐Carbon Quaternary Stereocenters via Asymmetric Cyclopropanations: Synthesis of Chiral Carbocyclic Pyrimidine Nucleosides

“…The asymmetric intermolecular cyclopropanation reaction between olefins and diazo compounds is one of the most powerful strategies to synthesize optically active cyclopropanes. [8][9][10] In 2016, we reported a direct route for the synthesis of chiral carbocyclic pyrimidine nucleosides via the Ru(II)-Pheox catalyzed enantioselective cyclopropanation of N1-vinylpyrimidines with a-diazoesters. [11] With respect to a-diazoester reactants, when methyl 2-diazoacetate (R 1 = H) was used, the corresponding carbocyclic pyrimidine nucleoside products could be generated in good yields (71-96% yields), high diastereoselectivities (10:1-> 20:1 dr), and excellent enantioselectivities (96-99% ee) (Scheme 1a, i).…”

“…After that, the reaction temperature was further investigated and À50 8C was selected as the better reaction temperature, giving 3aa in 90% yield and 97% ee (entries 9-11). Subsequently, various solvents were tested in the presence of Rh-L7 at À50 8C, but the results were generally inferior to that in toluene (entries 10,[12][13][14][15][16]. When the catalyst loading was decreased from 4 to 2 mol%, excellent results (90% yield and 96% ee) could still be obtained (entries 10 and 17).…”

Synthesis and thermal transformations of pyrazolines obtained by 1,3-dipolar addition of diazocyclopropane to maleimides

“…7). The fragment of 2 amidocyclopropanecarboxylic acid was used in the development of pseudo tri and pentapeptides to make their conformational mobility limited, 8,9 as well as in the synthesis of bicyclic monothioimides, which are of interest as chiral synthons. 10…”