Base‐promoted Oxidative Sulfuration/Cyclization to Construct Naphtho[2,3‐d]thiazole through Three‐component Reaction Using S₈ as the Sulfur Source

Abstract

A base‐promoted three‐component oxidative sulfuration/cyclization reaction of 2‐amino‐1,4‐naphthoquinone, aldehyde and elemental sulfur was developed. The naphtho[2,3‐d]thiazole ring was determined by forming two C−S bonds and one C=N bond, which demonstrates the advantages of cheap raw materials, no transition metal, and economic efficiency. The substrate scope was broad with aromatic and aliphatic aldehydes. The mechanistic study might promote the reaction design for a oxidative sulfuration/cyclization reaction.

Naphthoquinone-Based Oxime Esters for Free Radical Photopolymerization under Sunlight or a Blue Light-Emitting Diode

“…2-Aminonaphthalene-1,4-dione R1 was obtained in one step by reaction of 1,4-naphthoquinone and sodium azide NaN 3 in acidic conditions and isolated in 64% yield . To obtain the precursor R6 of oxime ester OXE-0, a treatment of 1 equiv of R1 with 1 equiv of 4-(1,3-dioxolan-2-yl)-2,5-bis­(dodecyloxy)­benzaldehyde R2 in the presence of sulfur S8 and sodium hydrogenocarbonate NaHCO 3 was carried out according to the literature . Unfortunately, no trace of the expected product R6 was detected in the reaction mixture by 1 H NMR.…”

“…40 To obtain the precursor R6 of oxime ester OXE-0, a treatment of 1 equiv of R1 with 1 equiv of 4-(1,3-dioxolan-2-yl)-2,5-bis(dodecyloxy)benzaldehyde R2 in the presence of sulfur S8 and sodium hydrogenocarbonate NaHCO 3 was carried out according to the literature. 38 Unfortunately, no trace of the expected product R6 was detected in the reaction mixture by 1 H NMR. Instead of R6, another product was obtained despite the use of 1:1 ratio between the aminonaphthoquinone and the aldehyde, namely, the difunctional product 2,2′-(2,5-bis(dodecyloxy)-1,4phenylene)bis(naphtho[2,3-d]thiazole-4,9-dione) R3 that was isolated in low yield (19%).…”

“…In 2022, innovative synthesis was proposed by Li and co-workers consisting of a basepromoted oxidative sulfuration/cyclization reaction enabling facile construction of the thiazole ring by use of S 8 as the sulfur source. 38 In terms of photoinitiating systems, a great deal of effort has recently been devoted to simplifying the composition of the photocurable resins, and in this aim, type I photoinitiators are ideal candidates. Among type I photoinitiators, oxime esters are candidates of choice by their ease of synthesis and the possibility to synthesize these structures starting from an aldehyde and by the use of cheap reagents (hydroxylamine hydrochloride, sodium acetate, triethylamine, ...) to introduce oxime functionality.…”

“…From a synthetic viewpoint, naphtho­[2,3- d ]­thiazole-4,9-diones have been less studied than their 1 H -naphtho­[2,3- d ]­imidazole-4,9-dione analogues due to a more difficult synthetic access. In 2022, innovative synthesis was proposed by Li and co-workers consisting of a base-promoted oxidative sulfuration/cyclization reaction enabling facile construction of the thiazole ring by use of S 8 as the sulfur source …”

An efficient metal-free and catalyst-free C–S/C–O bond-formation strategy: synthesis of pyrazole-conjugated thioamides and amides

“…Fascinated by the immense pharmacological profiles of pyrazole, thioamide and amide derivatives, it was envisaged to develop a practical approach towards the synthesis of pyrazolethioamide and pyrazole-amide conjugates. Elemental sulfur was explored as a sulfurating reagent for the generation of thioamides owing to its nontoxic, odorless nature and versatile reactivity profile [65][66][67][68][69][70][71][72][73][74][75][76]. To the best of our knowledge, the syntheses of pyrazole C-3/4/5-linked thioamide and amide conjugates have not been reported.…”