Isoxazole Strategy for the Synthesis of α-Aminopyrrole Derivatives

Abstract

The synthesis of methyl 5-aminopyrrole-3-carboxylates from 4-methyleneisoxazol-5-ones via "cyanide Michael addition/methylation/reductive isoxazole-pyrrole transformation" is developed. The last step occurs in a domino mode involving Mo(CO) 6 -mediated reductive isoxazole ring-opening, Mo(CO) 6catalyzed cis−trans-isomerization of the enamine intermediate followed by 1,5-exo-dig cyclization. 5-Amino-1H-pyrrolo-3-carboxylates react with 1,3-diketones, affording pyrrolo[1,2-a]pyrimidine-7-carboxylates, and are easily converted into 2-diazo-2H-pyrrole-4carboxylates. These compounds demonstrate the reactivity of both diazo compounds, giving pyrrole-containing products of intra/ intermolecular azo coupling, and carbenes to give pyrrole-containing insertion products into CH and OH bonds under photolysis.

Silica Supported Synthesis and Quorum Quenching Ability of Isoxazolones Against Both Gram Positive and Gram Negative Bacterial Pathogens

“…This protocol (Scheme 2) was further exploited to study its versatility, by subjecting various substituted aromatic aldehydes as well as heteroaromatic aldehyde to give corresponding Isoxazolones in very good yields (Table 2). Characterization studies of prepared compounds revealed parallel similarities with the reported literature data and undoubtedly supported the assigned structures [25–44] …”

“…Literature analysis [20–44,55–57] revealed this synthetic methodology to be one of the robust method for preparing Isoxazolone derivatives with more labile functional groups. Thus provide scope for development of functionally sensitive or even optically active Isoxazolones, keeping in mind their growing importance in medicinal field.…”

“…Characterization studies of prepared compounds revealed parallel similarities with the reported literature data and undoubtedly supported the assigned structures. [25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42][43][44] A probable mechanism for this silica supported transformation is given in Scheme 3. The role of silica is herein depicted for activating the dicarbonyl reactant as well as aldehyde and further facilitating the dehydration.…”

Recent Advancements in Pyrrole Synthesis

“…Literature survey on pyrrole synthesis between 2014 and 2019 also revealed interesting strategies in which different classes of heterocycles have been effectively employed as starting materials. [126][127][128][129][130][131][132][133][134][135] Some examples discussed in this section include münchnones, isoxazoles, carbohydrates, hydroxyprolines, and pyrrolines. It is interesting to note that these heterocyclic motifs readily produce pyrroles that are densely substituted.…”

On the Necessity of One‐Pot Tautomer Trapping in Asymmetric Michael Reactions of Arylideneisoxazol‐5‐ones

“…This is actually a limitation, not only for pharmaceutical applications, but it has also practical issues for product characterization, HPLC analysis and determination of diastereo‐ and enantiomeric ratios. As a consequence, Michael adducts of alkylideneisoxazol‐5‐ones have attracted a limited attention and they have mainly served as non‐isolated intermediates in further transformations , , , , …”