Clauson–Kaas pyrrole synthesis using diverse catalysts: a transition from conventional to greener approach

• Dileep Kumar Singh and
• Rajesh Kumar

Beilstein J. Org. Chem. 2023, 19, 928–955, doi:10.3762/bjoc.19.71

• is an important aromatic heterocyclic scaffold found in many natural products and predominantly used in pharmaceuticals. Continuous efforts are being made to design and synthesize various pyrrole derivatives using different synthetic procedures. Among them, the Clauson–Kaas reaction is a very old and

• acid catalysts and transition metal catalysts. The goal of this review is to summarize the synthesis of various N-substituted pyrrole derivatives using a modified Clauson–Kaas reaction under diverse conventional and greener reaction conditions. Keywords: catalyst; Clauson–Kaas pyrrole synthesis; 2,5

• comprehensive review on Clauson–Kaas pyrrole synthesis has not yet been published. Therefore, a review on this topic was required, describing various reaction conditions used in the Clauson–Kaas reaction. At the end, this review is divided into two sections. The conventional Clauson-Kaas pyrrole synthesis

Design, synthesis and photophysical properties of novel star-shaped truxene-based heterocycles utilizing ring-closing metathesis, Clauson–Kaas, Van Leusen and Ullmann-type reactions as key tools

• Shakeel Alvi and
• Rashid Ali

Beilstein J. Org. Chem. 2021, 17, 1374–1384, doi:10.3762/bjoc.17.96

• properties (absorption and emission) for these versatile systems has been revealed. Keywords: Clauson–Kaas reaction; heterocycles; ring-closing metathesis; truxene; Ullmann-type coupling; Van Leusen reaction; Introduction The two-dimensional phenylene-based π-conjugated star-shaped architectures has

• -allylation sequences, which in turn was assembled from the commercially available 1-indanone (1) utilizing cyclotrimerization and subsequent alkylation reactions. On the other hand, the same compound 6 was generated form triaminotruxene 4 using three-fold Clauson–Kaas reaction which in turn was assembled

• the same compound 6 from the triamine 4 utilizing a three-fold Clauson–Kaas reaction in the presence of 2,5-dimethoxytetrahydrofuran (10) under acetic acid reflux conditions (Scheme 3). Alternatively, the pyrrole-based system 6 has also been prepared starting from truxene (7) in three steps, involving

First synthesis of meso-substituted pyrrolo[1,2-a]quinoxalinoporphyrins

• Dileep Kumar Singh and
• Mahendra Nath

Beilstein J. Org. Chem. 2014, 10, 808–813, doi:10.3762/bjoc.10.76

• with various aromatic aldehydes followed by in situ KMnO4 oxidation to form target porphyrin analogues in good yields. The structures of all synthesized products were established on the basis of spectral data and elemental analyses. Keywords: Clauson–Kaas reaction; fluorescence; pyrrolo[1,2-a

• [1,2-a]quinoxalinoporphyrins (4a–h) is depicted in Scheme 1. At first, 5-(4-amino-3-nitrophenyl)-10,15,20-triphenylporphyrin (1) was synthesized from 5,10,15,20-tetraphenylporphyrin (TPP) after a series of reactions [46][49] in five steps. The Clauson–Kaas reaction of porphyrin (1) with 2,5