The selective oxidation of alcohols to aldehydes is a key reaction in organic chemistry for the synthesis of important building blocks for drugs, agrochemicals, flavors and fragrances. A rethinking towards green, environmentally friendly synthesis processes is taking place on an industrial scale, as a result of which the use of biocatalysts is gaining increasing attention. This research paper shows how efficient, selective biocatalysts can be for the oxidation of alcohols to aldehydes. Afterwards, cascade reactions were tested: an alternative to the Mitsunobu reaction; as well as a combination of biocatalyzed alcohol oxidation and 1,4-Michael addition from aldehydes to nitroolefins. In both cascades the first step corresponds to the biooxidation of alcohols to aldehydes. For the Mitsunobu reaction, the reductive amination of aldehydes to secondary amines using metal catalysts and reducing reagents such as hydrogen, formate or cyanoborohydride was investigated. one-pot stepwise? Cascades have been shown while? One-pot simultaneous-step? In addition, the use of Raney Nickel showed that a bio- and metal-catalyzed Mitsunobu alternative was not possible, since primary amines could be directly alkylated with amines or alcohols and the aforementioned metal catalyst One-pot combination of the oxidation of alcohols to aldehydes, which then react with nitroolefins in an organocatalyzed 1,4-Michael addition, was unsuccessful due to the complexity of the combination of a bio- and organocatalyzed reaction involved enzyme should be purified so that the cascade is possible. Furthermore, this part allowed us to see how universally cells can be used in both the biocatalyzed retro-Henry reaction and the reduction of aldehydes to alcohols.
The selective oxidation of alcohols to carbonyl compounds is a key reaction in organic chemistry, ranging from pharmaceuticals to agrochemicals, throughout flavoring and fragrance materials.Due to regulations, industries are developing green environmentally-friendly syntheses.Thus, the use of biocatalysts has received increased In a further step, cascades were tested: an alternative to the Mitsunobu reaction as well as a combination of biocatalysed alcohol oxidation and 1,4 -Michael addition of aldehydes to nitroolefins. In both cascades, the first step corresponded to the biooxidation of alcohols to aldehydes. As the Mitsunobu alternative is concerned, the second step, reductive amination of aldehydes to secondary amines, was investigated in the presence of metal catalysts and reducing agents like dihydrogen, formate or cyanoborohydride. Many one-pot stepwise cascades are shown h ere while one-pot simultaneous-step cascades displayed low results due to the system complexity. Furthermore, the use of Raney nickel metal catalyst showed that a bio and metal catalysed Mitsunobu alternative was not feasible, since primary amines could be directly alkylated to secondary amines in the presence of amines or alcohols and the quoted metal catalyst.As for the one-pot simultaneous-step combination of a biooxidation of alcohols to aldehydes which are then added to nitroolefins in a 1,4-Michael organocatalysed addition, no real success was achieved because of the complexity of both biocatalysed and organocatalysed parts which interfered with each other.However, the study of side-reactions enabled us to conclude that the enzyme will have to be purified to perform such a cascade.Furthermore, this last part enabled us to see how powerful cells can be in the biocatalysed retro-Henry reaction as well as reduction of aldehydes to alcohols.
|The PDF document was 5 times downloaded.|