Conversion of Aryl Methyl Ketimines to 2,5-Diarylpyrroles Using TiCl₄/Et₃N

Well‐defined NHCPd complex‐mediated intermolecular direct annulations for synthesis of functionalized indoles (NHC = N‐hetero‐cyclic carbene)

“…[6] The previous study has showed that a lone, potentially reactive Cl substituent does not carry out relative α-arylation of ketone under those reaction conditions, which supports an enamine-Heck mechanism (path b). [7] In the present study, we observed further that isolated enamine, prepared by condensation of o-bromoanile with acetophenone mediated by a TiCl 4 /TEA system, [25] was able to be cyclized to afford the 2-phenylindole in an overall yield of 72% by utilizing the present catalytic protocol (Scheme 6).…”

An Efficient and Green Procedure for Synthesis of Pyrrole Derivatives by Paal–Knorr Condensation Using Sodium Dodecyl Sulfate in Aqueous Micellar

“…Pyrroles are an important class of heterocyclic compounds and are structural units found in a vast array of natural products, synthetic materials, and bioactive molecules, such as heme, vitamin B 12 , and cytochromes . Classical methods for their preparation include the Knorr , Hantzsch , and Paal–Knorr condensation reactions . One of the most common approaches to pyrroles synthesis is the Paal–Knorr reaction in which 1,4‐dicarbonyl compounds are converted to pyrroles in the presence of primary amines.…”

“…In this reaction, the 1,4‐dicarbonyl compounds provide the four carbons of the pyrroles with the possible substitutes, whereas the amine provides the nitrogen with its substituent. Many catalysts have been used for this conversion such as montmorillonite KSF , microwave irradiation , Bi(NO 3 ) 3 .5H 2 O , Sc(OTf) 3 , TolSO 3 H , layered zirconium phosphate and zirconium sulfophenyl phosphonate , titanium , or TiCl 4 /Et 3 N . Some of other methods for synthesis of pyrroles include: conjugate addition reactions , annulation reactions , multicomponent reactions , and aza‐Wittig reactions .…”

Novel Synthesis of Substituted Pyrrole Bound to Indolinone via Molecular Iodine-Catalyzed Reaction

“…3 These compounds have also been prepared from transition metal intermediates, 4 by reductive couplings, 5 aza-Wittig reactions, 6 and other multistep operations. 7 However, the PaalKnorr reaction 8 remains one of the most attractive and simple methods for the synthesis of pyrroles. A clay-mediated 9 reactions and microwave irradiation method 10 have been used for the construction of pyrroles following Paal-Knorr conditions.…”