Synthesis, Structure, and Complexation Properties of Partially and Completely Reduced meso-Octamethylporphyrinogens (Calix[4]pyrroles)

Cu(II)-Catalyzed Reaction of Ethynyl Methylene Cyclic Carbamates and Amines: Synthesis of Polysubstituted Pyrroles

A copper-catalyzed efficient, operationally simple, general method for straightforward syntheses of polysubstituted pyrroles employing ethynyl methylene cyclic carbamates as precursors reacting with commercially available amines was first reported. A wide variety of polysubstituted pyrroles were obtained in acceptable to good yields under mild conditions. This protocol features broad substrate scope, high functional group tolerance, and easy operation, therefore enabling late-stage functionalization and rapid synthesis of bioactive compounds, including structurally complex marketed drugs and natural products. In addition, a scale-up experiment further highlighted the synthetic utility.

Ag-Catalyzed Switchable Synthesis of Site-Specifically Functionalized Pyrroles via Azafulvenium Intermediates

Here, we present a versatile, silver-catalyzed multi-auto-tandem reaction involving enamines, alkynals, and nucleophiles, utilizing the highly reactive intermediate azafulvenium. This method allows for flexible and switchable regiodivergent reactions through either intermolecular or intramolecular nucleophilic attacks, which can be controlled by adjusting the catalytic conditions. A range of site-specific functionalized or polycyclic fused pyrrole products were efficiently produced with a high level of chemocontrol.

Synthesis of N-, O-, and S-heterocycles from aryl/alkyl alkynyl aldehydes

In the field of heterocyclic synthesis, alkynyl aldehydes serve as privileged reagents for cyclization reactions with other organic compounds to construct a broad spectrum of N-, O-, and S-heterocycles. Due to the immense application of heterocyclic molecules in pharmaceuticals, natural products, and material chemistry, the synthesis of such scaffolds has received wide attention. The transformations occurred under metal-catalyzed, metal-free-promoted, and visible-light-mediated systems. The present review article highlights the progress made in this field over the past two decades.

Synthesis, odor characteristics and biological evaluation of N-substituted pyrrolyl chalcones

Base-mediated transition-metal free α-functionalization of N-substituted acetylpyrroles with commercial alcohols to generate various pyrrolyl chalcones is reported, and several prominent bioactive and flavor molecules were obtained.

A new entry to highly functionalized pyrroles via a cascade reaction of α-amino esters and alkynals

Here, we developed an expedient access route to highly functionalized pyrroles from readily available α-amino acid ester hydrochlorides and alkynals via a cascade condensation/intramolecular cyclization followed by a unique C-N ester migration process. A variety of 1,2,3-trisubstituted pyrroles, which were difficult to acquire with the common methodologies, were successfully prepared in good yields under mild conditions.

An organocatalytic method for constructing pyrroles via the cycloisomerisation of Z-1-iodo-4-N-methylbenzenesulfonyl-1,6-enynes

A new cycloisomerisation of Z-1-iodo-4-N-methylbenzenesulfonyl-1,6-enynes to functionalized pyrroles was realized in the presence of an organomolecule (4,4'-bis(1,1-dimethylethyl)-2,2'-bipyridine) and KOtBu. The transformations were performed efficiently to produce different kinds of functionalized pyrroles within 10 min. This is the first example of an organomolecule promoted methodology with vinyl iodides from a non-aromatic system to an aromatic system, which offers an excellent option toward establishing a new horizon for cross-coupling reactions of vinyl halides. Preliminary mechanistic studies were performed and a crude radical pathway was proposed.

Iron-Mediated Annulation between Methylene Ketones and Diethanolamines: A Sustainable and Scalable Procedure toward N-(2-Hydroxyethyl) Pyrroles

An iron-mediated direct annulation between methylene ketones and diethanolamines was developed for the efficient synthesis of N-(2-hydroxyethyl) pyrroles. This protocol shows high efficiency, operational simplicity, good functional group compatibility as well as broad substrates scope.

A new avenue to the synthesis of highly substituted pyrroles: synthesis from N-propargylamines

Pyrroles have attracted much attention due to their potential biological activities.

Magnetically recoverable Cu0/Fe3O4catalyzed highly regioselective synthesis of 2,3,4-trisubstituted pyrroles from unactivated terminal alkynes and isocyanides

An efficient, one pot tandem, Cu⁰/Fe₃O₄catalyzed highly regioselective synthesis of 2,3,4-trisubstituted pyrroles from unactivated terminal alkynes and isocyanides.

Three-component reaction between substituted 2-(2-nitrovinyl)-phenols, acetylenedicarboxylate and amines: diversity-oriented synthesis of novel pyrrolo[3,4-c]coumarins

The diversity-oriented synthesis of pyrrolo[3,4-c]coumarins via FeCl₃-promoted three component reaction between substituted 2-(2-nitrovinyl)phenols, acetylenedicarboxylate and amines has been developed.

Substrate induced diastereoselective hydrogenation/reduction of arenes and heteroarenes

Nature/structure of the (hetero)arene, substituent and reducing agent affect the diastereoselectivity.

Nano-copper catalysed highly regioselective synthesis of 2,4-disubstituted pyrroles from terminal alkynes and isocyanides

Nano-copper(0) stabilized on alumina prepared from Cu–Al hydrotalcite has been reported for completely regioselective synthesis of 2,4-disubstituted pyrroles from unactivated terminal aromatic/aliphatic alkynes and isocyanides.

Phase-transformation-induced twinning of an iron(III) calix[4]pyrrolidine complex

The title compound, tetrachlorido-1κCl;2κ(3)Cl-(2,2,7,7,12,12,17,17-octamethyl-21,22,23,24-tetraazapentacyclo[16.2.1.1(3,6).1(8,11).1(13,16)]tetracosane-1κ(4)N,N',N'',N''')-μ2-oxido-diiron(III), [Fe2Cl4O(C28H52N4)], undergoes a slow phase transformation at ca 173 K from monoclinic space group P2(1)/n, denoted form (I), to the maximal non-isomorphic subgroup, triclinic space group P1, denoted form (II), which is accompanied by nonmerohedral twinning [twin fractions of 0.693 (4) and 0.307 (4)]. The transformation was found to be reversible, as on raising the temperature the crystal reverted to monoclinic form (I). In the asymmetric unit of form (I), Z' = 1, while in form (II), Z' = 2, with a very small reduction (ca 1.8%) in the unit-cell volume. The two independent molecules (A and B) in form (II) are related by a pseudo-twofold screw axis along the b axis. The molecular overlay of molecule A on molecule B has an r.m.s. deviation of 0.353 Å, with the largest distance between two equivalent atoms being 1.202 Å. The reaction of calix[4]pyrrolidine, the fully reduced form of meso-octamethylporphyrinogen, with FeCl3 gave a red-brown solid that was recrystallized from ethanol in air, resulting in the formation of the title compound. In both forms, (I) and (II), the Fe(III) atoms are coordinated to the macrocyclic ligand and have distorted octahedral FeN4OCl coordination spheres. These Fe(III) atoms lie out of the mean plane of the four N atoms, displaced towards the O atom of the [OFeCl3] unit by 0.2265 (5) Å in form (I), and by 0.2210 (14) and 0.2089 (14) Å, respectively, in the two independent molecules (A and B) of form (II). The geometry of the [OFeCl3] units are similar, with each Fe(III) atom having a tetrahedral coordination sphere. The NH H atoms are directed below the planes of the macrocycles and are hydrogen bonded to the coordinated Cl(-) ions. There are also intramolecular C-H···Cl hydrogen bonds present in both (I) and (II). In form (I), there are no significant intermolecular interactions present. In form (II), the individual molecules are arranged in alternate layers parallel to the ac plane. The B molecules are linked by a C-H···Cl hydrogen bond, forming chains along [100].

4-Chlorobenzoyl-meso-octamethylcalix[2]pyrrolidino[2]pyrrole: an acyl chloride derivative of a partially reduced calix[4] pyrrole

In the title compound, C₃₅H₄₇ClN₄O, the two pyrrolidine rings have envelope conformations. The conformation of the macrocycle is stabilized by N—H⋯N hydrogen bonds and a C—H⋯N inter­action. The benzoyl ring is inclined to the adjacent pyrrole ring by 11.66 (11)°, with a centroid–centroid distance of 3.7488 (13) Å. In the crystal, molecules are linked by N—H⋯O hydrogen bonds into helical chains propagating in [010] and C—H⋯O and C—H⋯π interactions are also observed.

2-[2-(pyrrolidin-2-yl)propan-2-yl]-1H-pyrrole and its amide derivative 1-{2-[2-(1H-pyrrol-2-yl)propan-2-yl]pyrrolidin-1-yl}ethanone

In the title compounds, C(11)H(18)N(2), (II), and C(13)H(20)N(2)O, (III), the pyrrolidine rings have twist conformations. Compound (II) crystallizes with two independent molecules (A and B) in the asymmetric unit. The mean planes of the pyrrole and pyrrolidine rings are inclined to one another by 89.99 (11) and 89.35 (10)° in molecules A and B, respectively. In (III), the amide derivative of (II), the same dihedral angle is much smaller, at only 13.42 (10)°. In the crystal structure of (II), the individual molecules are linked via N-H...N hydrogen bonds to form inversion dimers, each with an R(2)(2)(12) graph-set motif. In the crystal structure of (III), the molecules are linked via N-H...O hydrogen bonds to form inversion dimers with an R(2)(2)(16) graph-set motif.