Heterocycles via Oxime Cycloadditions

Gold(I)-Catalyzed Enantioselective Annulations between Allenes and Alkene-Tethered Oxime Ethers: A Straight Entry to Highly Substituted Piperidines and aza-Bridged Medium-Sized Carbocycles

“…In the particular case of gold catalysis, the use of oxime ethers has been limited to a handful of isolated examples . On the other hand, it is striking that, despite imines having been exploited in several types of catalytic annulation reactions, oxime ethers (and esters) have been barely investigated in these types of transformations. , …”

Oximes: Chemical Properties, Methods of Preparation and Applications in Synthesis of Nitrogen Functional Groups

“…Essas espécies são preparadas a partir, respectivamente, da alquilação do nitrogênio de oximas e por desidrohalogenação de haloximas. 78 As nitronas e óxidos de nitrila participam de reações de adição nucleofílica, sendo assim, empregados na síntese de várias moléculas de origem natural e biologicamente ativas. Dentre estas reações, a cicloadição 1,3 com alcenos é uma das mais importantes, visto que geram anéis isozaxolínicos de forma regiosseletiva e estereoespecífica, 40 Os anéis isozaxolínicos são utilizados na síntese de várias substâncias que apresentam relevante atividade biológica, tais como: alcaloides, antipirético, bactericida, analgésico, nucleosídeo, antibióticos, lactamas, entre outros.…”

“…Cicloadição 1,3-dipolar de nitronas com alcenos e alcinos Alcenos e alcinos são excelentes dipolarófilos nas reações de cicloadiação 1,3 com óxidos de nitrila, os quais podem produzir isoxazolinas e isoxazóis, respectivamente. Os dipolos 1,3, em geral, são gerados in situ em razão de sua alta reatividade e capacidade de dimerização, 78,82 Esquema 18. Além de originar heteropentaciclos, os óxidos de nitrila podem formar 1,2,5oxadiazol 4-óxidos, 1,2,4-oxadiazol 4-óxidos e 1,4,2,5-dioxadiazinas.…”

Addition and Cycloaddition Reactions of Phosphinyl- and Phosphonyl-2H-Azirines, Nitrosoalkenes and Azoalkenes

“…Depending on the substituents, azoalkenes are sometimes stable enough to be isolated. Anyway, being isolated or generated “ in situ ”, the most common, general and broad scope method for the obtention of nitroso- and azo-alkenes is the base induced 1,4-dehydro elimination from oximes and hydrazones bearing a suitable halogen or ester leaving group at the α -position [ 1 , 2 , 4 , 7 , 10 , 11 ] ( Scheme 17 ).…”

“…The electrophilic character of these structures also allows cycloaddition reactions, particularly those with nucleophilic olefins, to take place under very mild conditions. Such reactions have provided routes to a variety of novel heterocyclic structures which have proved to be very useful targets, not only due to their eventual biological and pharmacological properties, but especially to their wide and versatile use as synthetic intermediates or useful building blocks for the synthesis of amino acids, pyrroles, proline, indoles, pyrazines, and aza-sugars derivatives, amongst many other compounds [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 ].…”