Alkil çinko ve -magnezyum bileşiklerinin allilik sübstitüsyon reaksiyonlarının sentetik ve alkil çinko bileşiklerinin allilik sübstitüsyon reaksiyonlarının mekanistik araştırılmas
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Date
2008
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Fen Bilimleri Enstitüsü
Abstract
The regioselectivity of Cu(I) catalyzed allylation of alkylzinc halides, dialkylzincs and bromomagnesium trialkylzincates has been investigated throughly with the aim of developing full regiocontrol depending on reaction parameters. The same regioselectivity can be obtained in the CuI catalyzed allylic coupling of n-butylzinc reagents in THF prepared by either pre-transmetallation or in situ transmetallation of Grignard reagents in the presence of allylic partner and catalyst. n-Butylzinc bromide and di n-butylzinc undergo g-selective allylation in THF at room temperature. The copper catalyst and coordinating solvents do not make an appreciable change on the yield and regioselectivity of the allylation of mono and dialkylzinc reagents. Bromomagnesium tri n-butylzincate gives preferential a-selectivity. The copper catalyst and coordinating solvents change regioselectivity. A mechanism has been also offered for a-selective allylic coupling of catalytic and stochiometric mono and dialkylzinc-copper reagents by evaluating their reactivity profiles.As an atom economic allylation, Cu(I) catalyzed alkyl-allyl coupling of in situ prepared alkyl Grignard reagents has been investigated in detail. Magnesium-Barbier type CuCN catalyzed allylation occurs regioselectively and affords predominantly the g-products in good to high yields. This one pot CuCN catalyzed reaction utilizing Mg, an alkyl halide and an allylic halide in THF at room temperature provides a practical four component reaction for synthesis of alkenes.
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Keywords
Alkil Halojenür, Allilleme