Microwave mediated facile one-pot synthesis of polyarylpyrroles from but-2-ene- and but-2-yne-1,4-diones

Pd/C Catalysis under Microwave Dielectric Heating

“…(i) some examples of a rapid cinnamate hydrogenation [56] (ii) the preparation of a key intermediate (57) for the first synthesis of the unusual nitrogen-containing N-(3-carboxylpropyl)-5-amino-2-hydroxy-3-tridecyl-1,4-benzoquinone isolated from Embelia ribes [57]; (iii) the synthesis of novel selective σ1 opioid ligands (59) [58]; (iv) the preparation of an intermediate (61) for synthesis of fluorinated cyclic β-amino acid [59] (Scheme 18).…”

“…The reaction was performed under Pd/C catalysis in polyethylene glycol-200 (PEG-200) under MWs using ammonium formate or alkyl/arylammonium formates, as a joint source of reductant and nitrogen nucleophile for the ring closure (Scheme 19) [61]. Reduction of aromatic nitro derivatives has also been accomplished on different aromatic or heteroaromatic nitro derivatives (65, 67, and 69, Scheme 20) using ammonium formate and catalytic transfer hydrogenation in ethanol [62][63][64][65].…”

“…MW-assisted reduction of arylnitro derivatives yielded the corresponding anilines that were submitted "in situ" to a Pictet-Spengler-type condensation with different ketones furnishing these novel heterocycle scaffolds [66]. The reaction was performed under Pd/C catalysis in polyethylene glycol-200 (PEG-200) under MWs using ammonium formate or alkyl/arylammonium formates, as a joint source of reductant and nitrogen nucleophile for the ring closure (Scheme 19) [61].…”

The Application of Iron (Iii) Phosphate in the Synthesis of N-Substituted Pyrroles

“…Consequently, many methods for the synthesis of diversely substituted pyrroles have been developed such as montmorillonite, KSF 12 , microwave irradiation 13,14 , Bi(NO 3 ) 3 .5H 2 O 15 , Sc(OTf) 3 16 , TolSO 3 H 17 , layered zirconium phosphate and zirconium sulfophenyl phosphonate 18 , titanium 19 or TiCl 4 /Et 3 N 20 . Some of other methods for synthesis of pyrroles include: conjugate addition reactions 21 , annulation reactions 22,23 , multicomponent reactions 24,25 and aza-Wittig reactions 26 .…”

Microwave-assisted Heterocyclic Chemistry

“…Ammonium formate or aryl/alkyl ammonium formates were employed both as reducing agents in the palladium-catalyzed transfer hydrogenation and also as sources of ammonia. Poly(ethylene glycol)-200 (PEG-200) was identified as the most convenient solvent for the microwave-assisted reaction owing to its high dielectric constant (ε = 20), high boiling point (> 250 • C) and excellent water miscibility (Scheme 4) [23]. Tetrasubstituted pyrroles could be obtained by skeletal rearrangement of 1,3-oxazolidines, a reaction that is substantially accelerated by microwave irradiation.…”