Microwave-Assisted Synthesis of 2-Substituted 2-Thiazolines and 5,6-Dihydro-4H-1,3-thiazines

Abstract

An efficient and general method for the synthesis of 2-substituted thiazolines and 5,6-dihydro-4H-1,3-thiazines is developed via microwave-assisted ring closure of ω-thioamidoalcohols promoted by ethyl polyphosphate (PPE). The cyclization reaction involves an SN2-type mechanism and features the advantages of very short reaction times, high yields and a predictable stereochemical outcome. The acyclic precursors are prepared in high overall yields by an improved diacylation–thionation–saponification sequence from commercially available ω-amino­alcohols. The whole process is metal-free and operationally simple.

Polyphosphoric Acid Esters Promoted Synthesis of Quinazolin-4(3H)-imines from 2-Aminobenzonitrile

“…23,24 We have used these reagents to promote intramolecular reactions leading to heterocyclic amidines, 25 dihydroquinazolines, 26,27 amidine Noxides, 28 2-iminoazacyclohexanes, 23 oxazolines, 24 and their higher homologues. 29,30 In this work, we investigate the use of PPA esters in the synthesis of QIs from 2-ABN and easily available secondary amides. possible isolation of the corresponding 4(3H)-quinazolinone 4 or N-substituted-4-aminoquinazoline 5 (Scheme 2).…”

“…These mild reagents, which are soluble in many organic solvents, activate nitrogen and oxygen containing functional groups toward nucleophilic attack. These features make them useful in transformations where other Lewis acids are not effective. , We have used these reagents to promote intramolecular reactions leading to heterocyclic amidines, dihydroquinazolines, , amidine N- oxides, 2-iminoazacyclohexanes, oxazolines, thiazolines, and their higher homologues. , In this work, we investigate the use of PPA esters in the synthesis of QIs from 2-ABN and easily available secondary amides.…”

Controlled Preparation of Hydrangea‐like 0.3Zn‐0.15Sn/CuO Catalysts for the Rochow‐Müller Reaction by Microwave‐Assisted Liquid‐Phase Synergistic Impregnation

“…[14,20,[22][23][24][25] To enhance the rates of reaction, improve yields, and simplify the prapartion process, microwave is being actively considered as a powerful synthetic tool. [26][27] This potential preparation method has seldom been investigated for catalysts in the Rochow-Müller reaction. In this work, hydrangea-like 0.3Zn-0.15Sn/CuO catalysts are prepared by microwave-assisted liquid-phase co-impregnation as a new approach.…”

“…To enhance the rates of reaction, improve yields, and simplify the prapartion process, microwave is being actively considered as a powerful synthetic tool [26–27] . This potential preparation method has seldom been investigated for catalysts in the Rochow‐Müller reaction.…”