Baeyer and Drewsen

Baeyer and Drewsen s Synthesis.—The synthesis of Baeyer and Drewsen shows the constitution the most clearly. Cinnamic aldehyde (p. 656) is CeHs—CH = CH—CHO. When the ortho-nilro substitution product of this compound is reduced we obtain the corresponding ortho-2imm.o cinnamic aldehyde. This by loss of water yields quinoline. 

Carbostyril.—If in the Baeyer and Drewsen synthesis cinnamic acid is used instead of cinnamic aldehyde the or//fo-amino derivative, by loss of water, yields a hydroxy quinoline known as carbostyril. 

Baeyer and Drewsen, ortho-Nitro Benzaldehyde.—A later synthesis of Baeyer and Drewsen was by the condensation of ortho-nitro benzaldehyde with acetone in the presence of sodium hydroxide. 

Baeyer and O. R. Jackson prepared indole derivatives by reducing o-nitro-phenylacetaldehyde and o-nitrobenzylketones. Baeyer and V. Drewsen by the action of alkali on o-nitrocinnamylformic acid prepared o-nitrobenzaldehyde, and by the reaction of this with acetone obtained indigo. 

Although chemical transformations in aqueous solutions are known, in general, the poor solubility of organic compounds in water avoids the use of aqueous solvents in chemical reactions. Some early examples of reactions in aqueous medium can be traced back to the Wohler s urea synthesis in 1828 [70] and the Baeyer-Drewsen indigo synthesis in 1882 [71], MCR protocols, as already stated, are very important for developing new pharmaceuticals and libraries of medicinal scaffolds. However, few examples for MCRs in water as the solvent have been reported in the literature. In this section, we will discuss some selected MCRs in water ... 

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