Synthesis of aryl-fused 1,4-oxathiepines from pyridinium 1,4-zwitterionic thiolates and vinylideneortho-quinone methides

Abstract

The synthesis of aryl-fused 1,4-oxathiepines from pyridinium 1,4-zwitterionic thiolates with ortho-alkynyl aromatic phenols has been achieved in good to excellent yields under mild conditions. The key reactive intermediates (i.e., vinylidene...

Recent advances in the cyclization reactions of pyridinium 1,n-zwitterions (n = 4 and 5): scope and mechanism

“…In 2022, Cheng's group employed pyridinium 1,4-zwitterionic thiolates 1 and ortho -alkynyl aromatic phenols 65 as substrates to synthesize 1,4-oxathiepine derivatives 66 in the presence of Et 3 N as the base in DCE at 50 °C (Scheme 16). 40 The reaction proceeded with broad substrate tolerance under mild reaction conditions, producing the desired products 66 in moderate to excellent yields. A gram-scale experiment gave the 1,4-oxathiepine product 66a in 98% yield, which demonstrated the practicability and high efficiency of this strategy.…”

Recent Progress in Heterocycle Synthesis: Cyclization Reaction with Pyridinium and Quinolinium 1,4-Zwitterions

“…A clever strategy for the synthesis of benzooxathiepines was devised by Cheng et al, who used Et 3 N as the base to enable (3 + 4) cycloaddition using pyridinium 1,4-zwitterions 1 and ortho -alkynyl aromatic phenols 62 . The reaction yielded aryl-fused 1,4-oxathiepines 63 in 65–99% yields ( Scheme 15 ) [ 75 ]. In the proposed mechanism, ortho -alkynyl aromatic phenol 62 converted into vinylidene ortho -quinone methide 64 in the presence of an optimal base, and the intermediate 64 reacted with pyridinium 1,4-zwitterion 1 to produce intermediate 65 through S -nucleophilic addition.…”

Synthesis of 5‐Trifluoromethylpyrroles from Heating‐Induced Annulation of Pyridinium 1,4‐Zwitterionic Thiolates with CF3‐Imidoyl Sulfoxonium Ylides

“…For example, the thiolate could be used as a five‐membered synthon to undergo [5+X] cycloaddition, in which the pyridine ring participated in the reaction [10d,f,g,11] . In addition, the thiolate could also act as a three‐membered synthon to take part in [3+X] cycloaddition reactions with pyridine as a leaving group [10a–c,h–j,12] . The development of other reactive substrates to couple with pyridinium 1,4‐zwitterionic thiolates for accessing structurally specific heterocyclic scaffolds is also worthwhile.…”