Functionalization methylene groups

The isomeric (3-lactam 25 with the functionalized methylene group in the para position instead of the ortho position is a poorer inhibitor than the previous molecule 24a (Table 11.4).34 Compounds belonging to the ortho series were therefore preferentially synthesized. 

The mechanism of the reaction, which is of the aldol type, involves the car-bonyl group of tlie aldehyde and an active methylene group of the anhydride the function of the basic catalyst B (acetate ion 0H3000 or triethylamine N(0,Hb)j) is to form the anion of the active hydrogen component, i.e., by the extraction of a proton from the anhydride ... 

Both the Clemmensen and the Wolff-Kishner reductions are designed to carry out a specific functional group transformation the reduction of an aldehyde or ketone carbonyl to a methylene group Neither one will reduce the carbonyl group of a carboxylic acid nor... 

Appreciable interaction between chromophores does not occur unless they are linked directly to each other, or forced into close proximity as a result of molecular stereochemical configuration. Interposition of a single methylene group, or meta orientation about an aromatic ring, is sufficient to insulate chromophores almost completely from each other. Certain combinations of functional groups afford chromophoric systems which give rise to characteristic absorption bands. 

From the chemical point of view, succinic acid and its anhydride are characterized by the reactivity of the two carboxyUc functions and of the two methylene groups. Uses range from pharmaceuticals to food, detergents, cosmetics, plastics and resins, plant growth regulators, textiles, photography, and gas and water treatment. 

The selective bromination of a ketone in the presence of another susceptible functional group was achieved in a diterpene synthesis 240). A competing bromination of an anisole ring could be avoided here through the use of a pyrrolidine enamine derivative for activation of the methylene group adjacent to the carbonyl function. 

To evaluate properties of basic catalysts, the Knoevenagel condensation over aluminophosphate oxynitrides was investigated [13]. In this reaction usually catalysed by amines, the solid catalysts function by abstraction of a proton from an acid methylene group, which is followed by nucleophilic attack on the carbonyl by the resultant carbanion, re-protonation of oxygen and elimination of water. The condensation between benzaldehyde and malononitrile is presented below. 

Lead tetraacetate can effect oxidation of carbonyl groups, leading to formation of a-acetoxy ketones,215 but the yields are seldom high. Boron trifluoride can be used to catalyze these oxidations. It is presumed to function by catalyzing the formation of the enol, which is thought to be the reactive species.216 With unsymmetrical ketones, products from oxidation at both a-methylene groups are found.217... 

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