Pyrroles enamino esters

The condensation of nitro ilkenes with enamino- ketones or enamino-esters CGrob-Camenisch reacdoni has been v/idely used for pyrrole synthesis fEq. 10.4. This process is now carried out v/ith resin-boiind enamino-ketones for combinatoriM syntheses of pyrroles. ... 

The condensation of nitroalkenes with enamino- ketones or enamino-esters (Grob-Camenisch reaction) has been widely used for pyrrole synthesis (Eq. 10.4).6a This process is now carried out with resin-bound enamino-ketones for combinatorial syntheses of pyrroles.6b... 

Examples of the coupling of enam-ines are rare [60]. In most cases, the enamines undergo methanolysis to form electroinactive aminoacetals prior to the coupling reaction. Enamino ketones or enamino esters, however, yield via dimerization of the radical cations and subsequent ring closure pyrrole derivatives... 

Anodic dimerizations of enamino esters (Scheme 56) or ketones may give symmetrically substituted pyrroles [78]. 

By addition of carbocyclic, acyclic and heterocyclic enamino ester to nitroalkenes and subsequent expulsion of the nitro group, pyrrole ester and fused derivatives are accessible82 (equation 58). 

From the spectroscopic data of Sections II,A-C it can be concluded that partially saturated heterocyclic /J-enamino esters possess a specific push-pull stabilization owing to the conjugation of electron-donating amino group and electron-withdrawing ester function.67 Push-pull stabilization is responsible for the remarkable stability of this class of compounds similar stabilization allows isolation of certain antiaromatic cyclobutadienes or nonaromatic o-quinodimethanes.68 2-Aminofurans, -pyrroles, and -thiophenes, because of their extremely large electron density, are generally unstable and sensitive... 

It is known that pyrroles can be synthesized by the Michael reaction of p-enamino ketones or esters and nitroalkenes followed by cyclization [186], but this methodology requires the... 

Huang, Liang et al. developed a direct Cul-catalyzed synthesis of polysubsti-tuted pyrroles from dialkyl ethylenedicarboxylates and -enamino ketones or esters in moderate to good yields with molecular oxygen (1 atm) (Scheme 8.5). Variation of N-substituents, aromatic ring, alkyl, and ester could be obtained smoothly. In this procedure, molecular oxygen was used as the oxidant and the C(sp )-H bond of the -enamino ketones was cleaved [15]. 

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