Copper complexes malonic acid

The utilization of copper complexes (47) based on bisisoxazolines allows various silyl enol ethers to be added to aldehydes and ketones which possess an adjacent heteroatom e.g. pyruvate esters. An example is shown is Scheme 43[126]. C2-Symmetric Cu(II) complexes have also been used as chiral Lewis acids for the catalysis of enantioselective Michael additions of silylketene acetals to alkylidene malonates[127]. 

Copper complexes of substituted malonic acids had no influence on the acute toxicity towards adult zebra fish [227], possibly due to stronger chelating groups at the gill epithelia. In contrast, hatching of zebra fish, which is already very sensitive to Cu2+ alone, was delayed in the presence of hydrophobic ra-hexade-cyl malonate, and was not influenced by the less hydrophobic benzyl malonate [227], Overall, it appeared that the toxicity of free Cu2+ and the Cu-hexadecyl malonate complex was additive [227],... 

Palmer, F. B., Butler, C. A., Timperley, M. H. and Evans, C. W. (1998). Toxicity to embryo and adult zebrafish of copper complexes with two malonic acids as models for dissolved organic matter, Environ. Toxicol. Chem., 17, 1538-1545. 

A different approach that even obviates the use of a preformed silyllithium reagent takes advantage of the cleavage of the Si-Si bond of a disilane by a copper salt. Hosomi and co-workers185 have reported on the reaction of various enones or enals 250 with hexamethyldisilane or l,l,2,2-tetramethyl-l,2-diphenyldisilane, catalyzed by copper(i) triflate-benzene complex (Scheme 61). The transformation requires heating to 80-100 °C in DMF or DMI and the presence of tri-/z-butylphosphine in order to stabilize the copper catalyst under these harsh conditions. The addition products 251 were obtained with high yield after acidic work-up. The application of the method to alkylidene malonates as the Michael acceptor was recently disclosed.1... 

Analogous alkylations with unsaturated ketones can also be effected with silica-supported benzenesul-fonic acid sodium salt or, with some stereoselectivity, using a chiral imidazolidinone organo-catalyst. Optical induction can also be achieved in the addition of indole to alkyhdene malonates using bisoxazoline copper(II) complexes. ... 

Copper.—The labile complexes [Cu(mal)2]2- and Cu(mal) (mal = malonate) undergo photolysis in solution to give acetate and carbon dioxide but Cu" is not permanently reduced.129 On flash photolysis, however, transient species assigned to Cu1 compounds were observed. Cu11 derivatives of carboxylic acids have been used in the preparation of photosensitive plates.130... 

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