Ketomethylene compounds

Dissolve 1 g. of the ketomethylene compound and 1 1 g. or 2 2 g. of pure benzaldehyde (according as to whether the compound may be regarded as RCOCHjR or as RCHjCOCHjR ) in about 10 ml. of rectified (or methylated) spirit, add 0 5 ml. of 5.N -sodium hydroxide solution, shake and allow the mixture to stand for about an hour at room temperature. The benzylidene derivative usually crystallises out or will do so upon scratching the walls of the vessel with a glass rod. Filter off the solid, wash it with a little cold alcohol, and recrystallise it from absolute alcohol (or absolute industrial spirit). 

The nucleophilic carbon of ketomethylene compounds can react with anhydrobases of different species in a basic medium. This reaction presents a narrow similitude with -CHj attack. The resulting dye, neut-rodimethine cyanine either mesomethyl-substituted or not. varies with the nature of the anhydro base (Scheme 30) (53. 54). 

Two different access routes are used, whether the leaving group is carried on thiazolium derivatives such as anilinovinyl (method A), acetanilidovinyl (method B), formyl methylene, or thioformylmethylene or on the ketomethylene compound (method C). The use of acid anhydride together with pyridine has been patented (method E). 

Synthesis and Properties. Polyquinolines are formed by the step-growth polymerization of o-aminophenyl (aryl) ketone monomers and ketone monomers with alpha hydrogens (mosdy acetophenone derivatives). Both AA—BB and AB-type polyquinolines are known as well as a number of copolymers. Polyquinolines have often been prepared by the Friedlander reaction (88), which involves either an acid- or a base-catalyzed condensation of an (9-amino aromatic aldehyde or ketone with a ketomethylene compound, producing quinoline. Surveys of monomers and their syntheses and properties have beenpubhshed (89—91). 

Cyanine Dyes Derived from ThiazoJium Salts TABLE 121. KETOMETHYLENE COMPOUNDS... 

Ketomethylene, 4-(4-anilinobu tadienyli-dene), in the synthesis of tetra-methine neutrocyanines, 63 Ketomethylene compounds, attack on trimethine cyanines, 62 in synthesis of zeromethine cyanines,... 

Condensation of 5-bromo-l,3-diphenyl-2-thiobarbituric acid, which is readily available by bro-mination of 1,3-diphenyl-2-thiobarbituric acid, with ketomethylene compounds affords the amides. These are cyclocondensed to pyridazinopyridazines by treatment with 60% N2H4 and ammonium acetate in acetic acid <88IJC(B)902>. 

The second method corresponds to moving the formyl group from the aldehyde intermediate to the methylene base, and is a standard method for preparing a merocyanine (the open form of a spiropyran). This method is useful for the reaction of the easily obtained and stable Fischer s aldehydes (2-formylmethyleneindolines) (1) with ketomethylene compounds such as 2-hydroxybenzofuran (2) or 2-hydroxybenzothiophene where the corresponding hydroxyaldehyde is difficult to obtain (Scheme 4). These two methods include the several routes to various symmetrical and unsymmetrical spiro(dipyrans).6... 

The first example of tandem oxidation and l,2-acetoxysulfenylation/l,2-disulfenylation of Baylis-Hillman (BH) alcohols was reported by Yadav et al. [20]. The reaction involves oxidation of BH alcohols with IBX in [bmim][Br] to give P-ketomethylene compounds, followed by Cul-imidazole catalyzed 1,2-acetoxy-sulfenylation with an organodisulfide and AcOH to afford vicinal acetoxysulfides in excellent yields with complete regioselectivity (Scheme 14.21). This reaction was tested in six different ionic liquid imidazolium salts. Among these ILs, [bmim][Br] dissolved IBX at room temperature and gave the best result in the one-pot oxidative reaction. After isolation of final products, the IL could be recycled for four times with up to 70% recovery and reused without any loss of efficiency. 

Yadav first reported a one-pot oxidative u tz-Markovnikov bromohydroxy-lation and bromoalkoxylation of MBH adducts, accomplished at room temperature using LiBr as the bromine source and 2-iodoxybenzoic acid (IBX) as the oxidant. The process involves oxidation of MBH adducts with IBX to give p-ketomethylene compounds in situ, which undergo highly regioselective vicinal... 

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