RESUMO
Effective desymmetrization in copper-catalyzed intramolecular C-H insertion reactions of α-diazo-ß-oxosulfones in the formation of fused thiopyran dioxides is described for the first time. The use of a copper-bis(oxazoline)-NaBARF catalyst complex system leads to formation of the major thiopyran dioxide stereoisomer with up to 98:2 dr and up to 98% ee. The effect of varying the bis(oxazoline) ligand, copper salt, and site of C-H insertion on both diastereo- and enantioselectivities of these intramolecular C-H insertion reactions has been investigated. Similarly, desymmetrization in the formation of a fused cyclopentanone proceeds with up to 64% ee. These results represent the highest enantioselectivity reported to date in a copper-mediated desymmetrization through C-H insertion.
RESUMO
Correction for 'Enantioselective copper catalysed intramolecular C-H insertion reactions of α-diazo-ß-keto sulfones, α-diazo-ß-keto phosphine oxides and 2-diazo-1,3-diketones; the influence of the carbene substituent' by Amy E. Shiely et al., Org. Biomol. Chem., 2017, 15, 2609-2628.
RESUMO
Enantioselectivities in C-H insertion reactions, employing the copper-bis(oxazoline)-NaBARF catalyst system, leading to cyclopentanones are highest with sulfonyl substituents on the carbene carbon, and furthermore, the impact is enhanced by increased steric demand on the sulfonyl substituent (up to 91%ee). Enantioselective intramolecular C-H insertion reactions of α-diazo-ß-keto phosphine oxides and 2-diazo-1,3-diketones are reported for the first time.
RESUMO
Enantio- and diastereoselective hydrogenation of ß-keto-γ-lactams with a ruthenium-BINAP catalyst, involving dynamic kinetic resolution, has been employed to provide a general, asymmetric approach to ß-hydroxy-γ-lactams, a structural motif common to several bioactive compounds. Full conversion to the desired ß-hydroxy-γ-lactams was achieved with high diastereoselectivity (up to >98% de) by addition of catalytic HCl and LiCl, while ß-branching of the ketone substituent demonstrated a pronounced effect on the modest to excellent enantioselectivity (up to 97% ee) obtained.
RESUMO
The novel preparation of 2-aminopyridoimidazoles and 2-aminobenzimidazoles via the cyclization of (2-aminopyridin-3-yl)urea and (2-aminophenyl)urea substrates in the presence of phosphorus oxychloride is described. This methodology is demonstrated for a range of urea substrates with aminoimidazole products obtained in good yields and with excellent levels of purity.
Assuntos
Aminopiridinas/síntese química , Benzimidazóis/síntese química , Imidazóis/síntese química , Ureia/análogos & derivados , Aminopiridinas/química , Catálise , Ciclização , Imidazóis/química , Estrutura Molecular , Ureia/síntese química , Ureia/químicaRESUMO
An efficient synthetic approach leading to introduction of the hydroxymethyl group to an aryl moiety via combination of the Bouveault formylation and hydride reduction has been optimized using a rational, mechanistic-based approach. This approach enabled telescoping of the two steps into a single efficient process, readily amenable to scaleup.
Assuntos
Aldeídos/síntese química , Morfolinas/síntese química , Álcool Feniletílico/síntese química , Antidepressivos/química , Humanos , Estrutura Molecular , Morfolinas/química , Álcool Feniletílico/análogos & derivados , Álcool Feniletílico/química , EstereoisomerismoRESUMO
Asymmetric copper-catalysed intramolecular C-H insertion reactions of a series of α-diazo-ß-keto sulfones are reported. Enantioselectivities of up to 82% ee were achieved in moderate to good yield. These results represent the highest level of enantiocontrol achieved to date for a copper-catalysed cyclopentanone synthesis via C-H insertion.