Rh(II)-mediated domino [4 + 1]-annulation of α-cyanothioacetamides using diazoesters: A new entry for the synthesis of multisubstituted thiophenes

Abstract

A new approach towards the synthesis of multisubstituted thiophenes is elaborated based on Rh(II)-catalyzed domino reactions of acyclic diazoesters with α-cyanothioacetamides. It provides a way for the preparation of 5-amino-3-(alkoxycarbonylamino)thiophene-2-carboxylates, 2-(5-amino-2-methoxycarbonylthiophene-3-yl)aminomalonates and (2-cyano-5-aminothiophene-3-yl)carbamates with the preparative yields of up to 67%. It was also shown that α-cyanothioacetamides easily interact with dirhodium carboxylates to give rather stable 2:1 complexes, resulting in an evident decrease in the efficiency of the catalytic process at moderate temperatures (20–30 °C).

[4+1] Cycloaddition of Enaminothiones and Aldehyde N‐Tosylhydrazones Toward 3‐Aminothiophenes

“…Interaction of aldehyde N ‐tosylhydrazone 2 with t BuOLi initially generates the intermediate diazo species 6 through Bamford‐Stevens reaction . Nucleophilic attack of the diazo carbon atom at the thiocarbonyl sulfur of enaminothione 1 forms thiocarbonyl ylide B , a sulfur‐centered 1,3‐dipole, which can tautomerize to exist in the form of species B′ , and then undergoes 1,5‐dipolar electrocycliza‐tion to form species C , furnishing a [4+1] cycloaddition. In the cases of using alkylthio, alkoxy, and primary amino‐fuctionalized enaminothiones, the leaving groups are the alkylthio, alkoxy, and primary amino, respectively.…”

Two Approaches for the Synthesis of Fused Dihydropyridines via a 1,6-Electrocyclic Reaction: Fluorescent Properties and Prospects for Application

“…Thioamides are building blocks widely used for the synthesis of nitrogen- and sulfur-containing heterocyclic compounds. − Thioamides can react with various monoelectrophilic, dielectrophilic, and ambient agents, such as α-halocarbonyl compounds and alkyl and alkenyl dihalides. − The CS bond of a thioamide group may react as a dienophile component in [4 + 2] cycloaddition reactions − and as a dipolarophile in the thermal and catalytic variants of 1,3-dipolar cycloaddition reactions. ,, Moreover, α-diazothioacetamides easily transform into 1,2,3-thiadiazoles by a 1,5-electrocyclic reaction. ,− …”