RESUMO
The reactions of aromatic aldehydes and levoglucosenone promoted by methoxide gives bridged α,ß-unsaturated ketones, formed by a series of oxa-Michael-initiated cascade reactions in yields of up to 91% (14 examples). A complex series of equilibria operate during the reaction, and the formation of the bridged species is thermodynamically favored, except in the case of 5-methylfurfural and pyrrole-2-carboxaldehyde. This is the first report detailing this type of aldol/Michael cascade involving oxa-Michael initiation.
RESUMO
The reactivity of 2-trichloromethylbenzoxazoles toward various nucleophiles, under metal-free or iron-catalyzed conditions, for the synthesis of substituted benzoxazoles is described. These methods allow for selective substitution at either the 2- or 2'-position of the benzoxazoles using the same starting materials/reagents. This approach allows for the controlled synthesis of a variety of key derivatives from a single 2-trichloromethylbenzoxazole starting material.
