Benzophenones complex derivatives

Among the many organic compounds recently proposed for the photostabilization of polymers, derivatives of benzophenone, complex esters of salicyclic acid, derivatives of benzotriazole, various organic tin compounds, thlazolidones, etc. are finding use. The last two classes of compounds are not considered in this chapter, since the methods of synthesis, properties, and use of organic tin compounds [1, 2] and thiazo-lidones [3, 4] have been rather fully treated in the literature. 

That charge-transfer effects are not involved follows from the fact that the rate of triplet decay in perfluorobenzene is larger than that in benzene. If the benzophenone triplet were to act as acceptor and the benzene derivative as donor in a charge-transfer complex, the substitution of perfluorobenzene for benzene should render this type of process much less probable due to the strongly electron-withdrawing character of the fluorine atoms. 

Ma and co-workers extended use of chiral guanidine catalysts to the addition of glycine derivatives to acrylates [121], Addition products were achieved in high yield with modest enantioselectivity (Scheme 67). The ferf-butyl glycinate benzophenone imines generally provided better enantiomeric ratios than the ethyl glycinate benzophenone imines. Based on this observation, the authors hypothesized that an imine-catalyst complex determines the stereochemical outcome of the product. 

A rather more complex scheme is required for the preparation of a derivative that bears a trifluoromethyl substituent on one of the benzene rings. The scheme starts with the condensation of the nitrile group in (32-1) with phenyhnagnesium bromide to give the corresponding imine treatment with aqueous acid leads to the substituted benzophenone (32-2). The future methyl on one of the bridges is introduced in a sequence involving the addition of a trimethylsulfonium yhde. 

Physical entrapment or chemical coupling is a well-established procedure for MIP preparation. First, a complex is formed between a functional monomer and template in an appropriate solvent solution. Then the complex is immobilized by polymerization in excess of a cross-linker. Predominantly, free-radical polymerization thermally launched with a 2,2-azobis(isobutyronitrile) (AIBN) initiator, is performed. In the case of photo-radical polymerization, a benzophenone or acetopho-none derivative is also used as the initiator [101]. Next, the template is extracted by rinsing the resulting MIP block with a suitably selected solvent solution. The bulk... 

The ligands NiV -bis-(2-aminoacetophenone)ettiylenediamine, NN -bis-(2-amino-benzophenone)ethylenediamine, and AiV -bis-(2-aminobenzaldehyde)ethylene-diamine (LH2) form mononuclear (CoLX) complexes and the more unusual bi- and tri-metallic derivatives (56) and (57).342... 

Optically active chromium tricarbonyl complexes can be lithiated and subsequently functionalized by a wide array of electrophiles with high diastereoselectivity. For example, reaction of (65) with a base and benzophenone gave (66) (Scheme 106). The sugar-derived complex (67)... 

The 1 1 reaction of ZnR2 with a-imino ketones R N=C(R")C(0)R" leads to quantitative formation of the dinuclear complexes [ZnR /it-A,O-N(R)(R )C(R")=C(R"0O ]2- The crystal structure of the derivative 238 has been reported. The reaction of [ZnEt(Cp)] and Et2NCH2C02Et gives 239, probably through the intermediate 240. The sodium dialkylamidozincate [(tmeda)Na(/ir-Bu-t)(/ir-TMP)Zn(Bu-t)] reacts with benzophenone to give 241. ... 

While aromatic aldimines of amino acid esters are readily accessible from benzaldehyde or related derivatives and amino acid esters with concomitant removal of water,the corresponding ketimines require harsher reaction conditions, e.g. the benzophenone imine of glycine methyl ester is formed in boiling xylene in the presence of boron trifluoride-diethyl ether complex as a Lewis acid in 82% yield.P l These or similar reaction conditions lead also to piperazine-2,5-dione (DKP) formation therefore milder reaction conditions have been developed such as the transimination with benzophenone imine in dichloromethane, which occurs at room temperature overnight in 80-95% yield (Scheme The N -diphen-... 

The relatively stable polymetallic Os3(CO)i2 (ref. 6) may be activated by conversion to anionic derivatives. Reduction of Os3(CO)j2 with potassium benzophenone gives the reactive, air-sensitive triosmium dianion [Osj(CO)i, ] . Generally, it is convenient to generate and use this complex immediately, without isolation Section B describes an example of this procedure... 

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