Asymmetric intramolecular cyclopropanation of diazo compounds with metallosalen complexes as catalyst: structural tuning of salen ligand
摘要:
Intramolecular cyclopropanation of alkenyl alpha-diazoacetates and alkenyl diazomethyl ketones was examined by using optically active (ON+)Ru(11)(salen) and Co(II)(salen) complexes as catalysts. For the cyclization of 2-alkenyl alpha-diazoacetates, Co(II)(salen) complexes 9 and 10 were found to be superior catalysts to the corresponding (ON+)Ru(11)(salen) complexes 4 and 5. On the other hand, (ON+)Ru(II)(salen) complex 2 was found to be the catalyst of choice for the cyclization of 3-alkenyl diazomethyl ketones, and complex 4 was found to be a good catalyst for the cyclization of (E)-4-alkenyl diazomethyl ketones. The present study demonstrates that metallosalen complexes, especially optically active (ON+)Ru(II)(salen) and Co(11)(salen) complexes, can serve as efficient catalysts for the cyclization of alkenyl diazocarbonyl compounds, if a suitable salen ligand is used as the chiral auxiliary. (C) 2003 Elsevier Science Ltd. All rights reserved.
α-Diazoacetates as Carbene Precursors: Metallosalen-Catalyzed Asymmetric Cyclopropanation
作者:Tsutomu Katsuki、Tatsuya Uchida
DOI:10.1055/s-2006-926448
日期:2006.5
Readily available α-diazo compounds have been shown to be efficient carbene precursors for asymmetric cyclopropanation using ruthenium(NO)-salen and cobalt-salen complexes, as catalysts. The stereoselectivity of the cyclopropanation depends on the metal ion, its valency, the structural and electronic nature of the salen ligand, and the apical ligand of the salen complex used. Both trans- and cis-selective asymmetric intermolecular cyclopropanation can be realized under mild conditions by using a suitable metallosalen complex. Furthermore, a wide range of alkenyl α-diazoacetates and the related alkenyl diazomethyl ketones undergo intramolecular cyclopropanation in a highly enantioselective manner by using various metallosalen complexes, easily prepared in a modular fashion, as catalyst.
Optically active Co(II)–salencomplexes (5 and 7) were found to catalyze highlyenantioselective intramolecular cyclopropanation of 2-alkenyl α-diazoacetates in the presence of N-methylimidazole under high substrate concentration.
Intramolecular Asymmetric Cyclopropanation with (Nitroso)(salen)ruthenium(II) Complexes as Catalysts
作者:Biswajit Saha、Tatsuya Uchida、Tsutomu Katsuki
DOI:10.1055/s-2001-9733
日期:——
Intramolecular cyclopropanation of (E)-2-alkenyl-α-diazoacetates was carried out with good to high enantioselectivity by using (nitroso)(salen)ruthenium(II) complexes as catalysts under photo-irradiation.
Cobalt-based catalysts for the cyclization of alkenes
申请人:Zhang Peter X.
公开号:US20060030718A1
公开(公告)日:2006-02-09
Metal-ligand complexes, including cobalt-ligand complexes, such as a cobalt-porphyrin complex, and their use as catalysts in the cyclization of alkenes.