Studies On Visible-Light-Promoted Intramolecular Oxyamidation Of Alkenes

1,2-Amino alcohols derivatives are highly-value, widely exist and well used in organic transformation for asymmetric catalysts, medicine, materials and so on. The direct oxyamination of alkenes is one of the most efficient methods to construct the 1,2-amino alcohol derivates. The diastereoselectivity-controllable oxyamination of same alkenes is a remaining challenge. Visible-light-promoted reactions are environment-friendly, often carried out under mild conditions, and have the ability to construct bonds which are not easily formed by using traditional methods. In this thesis, we wished to develop a diastereoselectivty-controllble oxyamination of alkenes via visible light photocatalysis. The details are summerized as following:N,O-Dicarbonyl hydroxylamine was chosen as both the nitrogen source and oxygen source. The intramolecular a-alkenyl hydoxylamines was selected. The initiate reaction was carried out by substrates used la as the model substrate in the presence of visible light photocatalyst, we optimized reaction conditions with various solvents, catalysts, temperatures and electron donors. Then we investigated the substrates scope with different characters, such as steric effect and electron effect. The relative configurations of products were determined by single crystal X-ray experiments. A series of reactions such as radical trapped reactions, time-course studies, isolation of intermediate, cross reactions and so on were conducted to elucidate the mechanism. The reactions could be carried out in gram-scale.1,2-Amino alcohol derivatives could be obtain with high regio- and diastereoselectivity under standard conditions. In the conditions with triethyl amine, the reactions could afford the anti-1,2-amino alcohol deveritives with 52-73% yield, up to >20:1 dr, while with triphenyl amine as a electrondonor, the N,O-dicarbonyl hydroxylamines could be coverted into syn-product with 47-93% yield, up to >20:1 dr. In the mechanism studies, firstly the reaction was likely to be a radical initiated reaction; secondly aziridines were the intermediates of the reactions; thirdly the diastereoselective of product could be controlled by the alkalinity of electron donors. The activity of the primary amidyl radical were better than that of the secondary amidy radicial. In the future, various difunctionalizations of alkenes via radical pathways are undergoing in our laboratory.