128388-81-8

Upstream product

• 917-54-4 methyllithium 
• 165554-70-1 6-ethoxy-3-phenyl-6H-1,2-oxazine 
• 928-55-2 ethyl 1-propenyl ether 
• 21572-32-7 2-chloro-1-phenyl-ethanone oxime 

Relevant academic research and scientific papers

Highly stereoselective and flexible synthesis of 6-alkoxy-5,6-dihydro-4h-1,2-oxazines by conjugate addition of organolithium compounds to 6h-1,2-oxazines followed by trapping with electrophiles

Conjugate additions of reactive organolithium compounds such as phenyllithium, n-butyllithium, tert-butyllithium, and 2-propenyllithium to 6H-1,2-oxazines 1, 24, and 25 followed by trapping of the intermediates with electrophiles gave a variety of highly substituted 6-alkoxy-5,6-dihydro-4H-1,2-oxazines 2-15 and 27-30 generally in very good yields. Most interestingly, this reaction sequence proceeds with high stereocontrol producing in large excess or exclusively the trans, trans-diastereomers. Using benzaldehyde as the electrophile, only compound 8, which is one of eight possible diastereomers, was formed. Methyllithium or lithiated methoxyallene as the nucleophilic component provide expected addition products 17 and 19, but formation of bis-1,2-oxazines 18 and 20 seems to be inevitable with these less reactive organolithium compounds.

On the Mechanism of Diels-Alder Reactions of Nitroso Alkenes: exo/endo Selectivity, Stereospecificity, E/Z Selectivity, and Relative Reactivity of Various Olefins

The mechanism of the hetero Diels-Alder reaction of nitroso alkenes 2 with silyl enol ethers and other olefins has been investigated.Using the bicyclic nitroso compound 2a a study of the exo/endo selectivity has demonstrated that the exo approach is preferred with the siloxyethene 1a as dienophile.On the other hand, the siloxycyclopentene 1c gives a mixture of cycloadducts 3c with an excess of endo product (endo:exo = 82:18).The stereospecificity of the nitroso alkene cycloaddition could be demonstrated with the stereochemically homogeneous silyl enol ethers 1b and 1d.Experiments with enol ethers 1f and 1g also occur stereospecifically. α-Nitrosostyrene 2b reveals surprisingly high kE/Z values when E/Z-isomeric olefins are compared in competition experiments.Also, a detailed reactivity scale of 2b including various structurally different silyl enol ethers and other typical dienophiles shows that a complex interplay of electronic and steric effects is operating.The large influence of steric effects is taken as evidence for a highly ordered transition state in the cycloaddition.All mechanistic details for the Diels-Alder reactions of nitroso alkenes 2 with (silyl) enol ethers are in strong accord with a concerted mechanism and exclude the involvement of zwitterions or diradicals as intermediates.