Synthesis of N -benzyl-des- D -ring lamellarin K via an acyl-Claisen/Paal-Knorr approach

Dehydrogenative Anodic Cyanation Reaction of Phenols in Benzylic Positions

“…2‐Phenylacetonitriles are amenable to a wide range of synthetic transformations, such as monoalkylation, reduction to 2‐phenylethyl‐amines, oxidation to acids or amides, conversion with azides to tetrazoles, or in Knoevenagel reactions with aldehydes to form alkenes (Scheme , Supporting Information) …”

“…2-Phenylacetonitriles represent important building blocks in organic synthesis and are precursors for biologically active molecules, such as tetrazoles [1] or 2-phenylethylamines, [2] including the fungicide mandipropamid, [3] and the calcium channel blocker verapamil (Scheme 1). [4] 2-Phenylacetonitriles are amenable to a wide range of synthetic transformations, such as monoalkylation, [5] reduction to 2-phenylethyl-amines, [6] oxidation to acids or amides, [7] conversion with azides to tetrazoles, [8] or in Knoevenagel reactions with aldehydes to form alkenes (Scheme 1, Supporting Information). [9] Electrochemical installation of cyano groups has been reported for electron-rich arenes several decades ago.…”

IBX-Promoted Oxidative Cyclization of N-Hydroxyalkyl Enamines: A Metal-Free Approach toward 2,3-Disubstituted Pyrroles and Pyridines

“…Among them, 2,3-disubstituted pyrroles and pyridines have attracted considerable attention, owing to their versatile applications in many vibrant research fields. , Examples are shown in Figure : (a) vitepyrroloids A , containing a 2-cyano-substituted pyrrole ring, isolated from the leaves of Vitex trifolia; (b) roseophilin, isolated from Streptomyces griseoviridis and identified as a novel protein tyrosine phosphatase inhibitor; (c) a pyrrole-fused benzosultam skeleton organic light-emitting diode material, which exhibits good photoelectric performance; (d) a synthesized 2,3-disubstituted pyridine, showing high PDE4 inhibitory activity; (e) and omeprazole, a successful proton pump inhibitor for the treatment of gastric ulcers. The common methods for the synthesis of these valuable targets rely on multistep synthesis, − Hantzsch reactions, , Parr–Knorr pyrrole synthesis, and Kröhnke pyridine synthesis . However, these methods usually are associated with problems such as requirement of toxic additives and catalysis, harsh reaction conditions, or low atom-economy.…”

Formation of 3,4‐Diarylpyrrole‐ and Pyrrolocoumarin Core of Natural Marine Products via Barton–Zard Reaction and Selective O‐Demethylation

“…Syntheses of the first category include successive introduction of aryl substituents into positions 3/4/5 of the pyrrole ring (mostly by metal‐catalyzed coupling reactions) and introduction of a carboxy group into position 2 . In the second approach the pyrrole ring is formed by various methods such as Grob cyclization, Paal‐Knorr and Hantsch reactions, interaction of α‐aminoester or α‐aminonitrile with α,β‐unsaturated carbonyl compounds, [3+2] dipolar cycloaddition, metal‐catalyzed [3+2] annulation, or the reductive recyclization of pyridazines…”

“…The coumarin (lactone) fragment might be present in the molecule before the pyrrole ring formation; in some cases these two rings are closed simultaneously,, but more often the lactone fragment is formed later than the pyrrole one – either from of O ‐aryl pyrrole‐2‐carboxylates (by intramolecular oxidative coupling[8a] or Heck reaction), or by intramolecular nucleophilic substitution of Br in 3‐(2‐bromophenyl)pyrrole‐2‐carboxylic acids,[9c], [10c], [12a] or by intramolecular C–H/O–H oxidative coupling of 3‐arylpyrrole‐2‐carboxylic acids. [9b], [11b], [11c], [11d], [12d] However, the most ubiquitous approach consists in lactonization of 3‐(2‐hydroxyphenyl)pyrrole‐2‐carboxylates, prepared from their O‐protected derivatives (PG = MOM, Bn,[10b], [10e] i Pr,[12c], Ac,[9a] Ms[11e]) (Scheme ) (this usually implies an introduction of the protective group as a separate step).…”