Isomiinchnones structures

Additional heterocyclic ring systems, such as benzofurans [125], dihydropyrroles and dihydroazepines [41], piperidines and dihydropyrimidines 36 [126], and fused oxazole derivatives [127], have been described (Eq. 7). The formation of epoxides and aziri-dines, formally emanating from ylides, was recently reported by Doyle et al. [77]. Rho-dium(II)-catalyzed isomiinchnone cycioaddition followed by Lewis acid-mediated ring opening has been used as an entry into the protoberberine azapolycyclic ring structure [128]. 

A number of bridged heterocyclic compounds have been prepared using the intramolecular cycloaddition of rhodium( 11)-generated isomiinchnones [51-53, 84, 129], as exemplified by the complex structure 37 [49, 53] and the tricyclic derivatives 38 and 39 (Scheme... 

Kappe et al. (166) employed an isomilnchnone generation-trapping sequence to access conformationally restricted dihydropyrimidine derivatives as novel calcium channel modulators. For example, the conformationally restricted analogues 269 were prepared via intramolecular cycloadditions from the isomiinchnones generated from a-diazo imides 268. The structures of these cycloadducts were established by X-ray crystallography. 

Our group has also encountered success in cycloadding an isomiinchnone dipole across an indole double bond [28]. Cycloadduct 91 was generated in high yield as a single diastereomer from the Rh2(OAc)4-catalyzed reaction of diazoimide 90. The assignment was unequivocally established by an X-ray crystal structure. The ready construction of these poly-heterocycles in one step and in... 

Oxazoles 1, benzoxazoles 2, oxazolium salts 3, and oxazole A -oxides 4 are fully conjugated compounds (Figure 1). In addition, the two mesoionic structures l,3-oxazolium-5-olates 5 and (l,3-oxazolium-4-olates) 6, commonly known as miinchnones and isomiinchnones, respectively, are also considered to be conjugated rings. There are five systems of hydroxyl-substituted oxazoles and they exist in their oxo forms the 2(3H)-, 2(5H)-, 4(5//)-, 5(2//)-, 5(4//)-oxazolones 7-11. Three forms of dihydrooxazoles are known 2,3-, 2,5-, and 4,5-dihydrooxazoles respectively 12-14. The fully saturated ring is called oxazoline 15. The monooxo derivatives are 2-oxazolidinone 16,4-oxazolidinone 17, and 5-oxazolidinone 18. The three variants of oxazolidinediones are 19-21 and the fully oxidized oxazolidi-netrione is 22. 

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