Regioselective Synthesis of Dihydrothiophenes and Thiophenes via the Rhodium-Catalyzed Transannulation of 1,2,3-Thiadiazoles with Alkenes

Abstract

A method for the regioselective synthesis of a wide range of dihydrothiophenes was developed from the rhodium-catalyzed transannulation of 1,2,3-thiadiazoles with aliphatic, aromatic, and heteroaromatic alkenes. Tandem rhodium-catalyzed transannulation of 1,2,3-thiadiazoles with alkenes followed by 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) oxidation was also demonstrated for the one-pot regioselective synthesis of various thiophenes. Advantages of the present method include a broad substrate scope, wide functional group compatibility, and high regioselectivity.

Progress in intermolecular and intramolecular reactions of thioamides with diazo compounds and azides

“…[45]. Ten years later, Gevorgyan and Kurandina [46] and subsequently the Lee group [47][48][49] have undertaken rhodium-catalyzed reactions of 1,2,3thiadiazoles with alkenes, alkynes and nitriles, including the intramolecular mode, that confirms the existence of an equilibrium between 1,2,3-thiadiazole 48 and its open chain isomer, diazo thioacetamide 47 (Scheme 14).…”

One‐Pot Synthesis of 2,3,5‐Trisubstituted Thiophenes through Three‐Component Assembly of Arylacetaldehydes, Elemental Sulfur, and 1,3‐Dicarbonyls

“…Recently, the transition‐metal‐catalyzed direct C−H arylation of thiophenes has found to be an efficient tool for the thiophene diversification ,. With respect to annulation reactions, non‐readily available starting materials such as functional mercaptans,thioamides,, dialkynes,– and 1,2,3‐thiadiazoles, were frequently employed to generate substituted thiophenes through intermolecular or intramolecular cyclization. Also, few examples of multicomponent reactions led to the construction of thiophene rings from readily available chemicals ,.…”

Chemoselectivity in the Transannulaction of 1,2,3‐Thiadiazoles and Alk‐2‐enenitriles: Specific Synthesis of 3‐(Alk‐1‐enyl)isothiazoles

“…For aliphatic ( E )‐but‐2‐enenitrile ( 2 n ) and acrylonitrile ( 2 o ), they gave the desired products 2 n and 2 o in very low yields. Although thiadiazole 1 a reacted with various terminal alkenes to afford dihydrothiophenes in good yields [4a] and acrylonitrile ( 2 o ) was a terminal cyanoetheane, no corresponding ethyl 4‐cyano‐2‐phenyl‐4,5‐dihydrothiophene‐3‐carboxylate was observed in careful analysis of the reaction mixture by GC‐MS. Geminal disubstituted acrylonitriles 2 p–2 r , including dialkyl, one alkyl and one aryl, and diaryl, also worked well, affording the desired products 3 ap – 3 ar in 60‐83 % yields.…”

“…These are supported by the similar observation in the transannulation of 1,2,3‐thiadiazoles with olefins, in which linear terminal olefins work well. However, internal and 1,1‐disubstituted alkenes such as trans ‐β‐methylstyrene and α‐methylstyrene do not work at all [4a] …”