Internal Nucleophilic Catalyst Mediated Cyclisation/Ring Expansion Cascades for the Synthesis of Medium‐Sized Lactones and Lactams

Abstract

Astrategy for the synthesis of medium-sized lactones and lactams from linear precursors is described in whicha n amine acts as an internal nucleophilic catalyst to facilitate an ovel cyclisation/ring expansion cascade sequence.T his method obviates the need for the high-dilution conditions usually associated with medium-ring cyclisation protocols,a s the reactions operate exclusively via kinetically favourable "normal"-sized cyclic transition states.T his same feature also enables biaryl-containing medium-sized rings to be prepared with complete atroposelectivity by point-to-axial chirality transfer.

A NaHCO3 Promoted Three‐component Cyclization: Easy Access to Benzodisulfide Heterocycles

“…In this newly developed three-component reaction, elemental sulfur (S 8 ) is inexpensive and user-friendly, [16,20] and 2-halophenylacetics are readily available. [29,31] Recently, Tang's group reported a decarboxylative multicomponent polymerization of p-phenylenediacetic acid, S 8 and aromatic diamines to convert S 8 into functional polythioamides with great structural diversity, large molecular weights and excellent yields. [32] Inspired by this, in the combination with our previous researches on the use of cheap inorganic bases in organic synthesis, [39,40] we utilized the decarboxylation of 2-halophenylacetic acids with a ring-forming reaction site in the presence of aromatic amines and S 8 as reactants to construct cyclic disulfide compounds.…”

“…[27] In a word, benzodisulfide heterocycles are of great interest from a chemical and biological points of view, but their 3-arylimino derivatives have been much less studied. [26] In comparison, due to their cheapness and availability, 2halophenylacetic acids and its derivatives are often used as synthons in organic synthesis, [28,29] including the synthesis of cyclic compounds. [30,31] However, there is no reports on the synthesis of sulfur-containing heterocycles.…”

“…In comparison, due to their cheapness and availability, 2‐halophenylacetic acids and its derivatives are often used as synthons in organic synthesis, [28,29] including the synthesis of cyclic compounds [30,31] . However, there is no reports on the synthesis of sulfur‐containing heterocycles.…”

Synthesis of Eight‐Membered Nitrogen Heterocycles via a Heterogeneous PtI2‐Catalyzed Cascade Cycloaddition Reaction of δ‐Aminoalkynes with Electron‐Deficient Alkynes

“…Previous simple transition metal catalyzed reactions are most homogeneous reaction, whereas for the heterogeneous reactions, the supported metal catalysts are usually involved, such as carbon, silica gel, Al 2 O 3 , Fe 2 O 3 , molecular sieves, or polymer supports . Moreover, as shown in the literature, this rare strategy of synthesizing 8‐membered ring via a cascade reaction, involving cyclisation of a linear molecule and in situ ring expansion of 6‐ b ‐4 fused rings to 8‐membered rings, has many advantages over the traditional direct end‐to‐end cyclization, such as offering excellent yields.…”

N-acylation of amides through internal nucleophilic catalysis

“…Recently, Unsworth demonstrated a strategy for the synthesis of medium-sized rings readily from linear precursors mediated by an internal nucleophilic catalyst, a pyridine ring, which can capture the carboxylic acid to provide a reactive intermediate (Scheme 1(b)). [21][22][23] Inspired by this work, we have taken advantage of internal catalysis to achieve mild N-acylation reactions of amides. Herein, we used the amides possessing a pyridine ring as substrates, the pyridine ring can form an active acylammonium salt with an acyl chloride.…”