Barbara Guidi

First preparation and reaction of polymer-bound 1,2-diaza-1,3-butadienes. A convenient entry to 4-triphenylphosphoranylidene-4,5-dihydropyrazol-5-ones

Abstract The first general protocol for the preparation of different polymer-bound 1,2-diaza-1,3-butadienes is reported. The utility of these supported reagents in the solid-phase synthesis of 4-triphenylphosphoranylidene-4,5-dihydropyrazol-5-ones by reaction with triphenylphosphine is presented.

2-Substituted 5-Acetyl-4-Thiazolyl Triflates as Useful Building Blocks for the Preparation of Functionalized Thiazoles

The readily available 2-substituted 5-acetyl-4-thiazolyl triflates 2are useful building blocks for the preparation of functionalised thiazoles by means of palladium-catalysed cross-coupling reactions with organometallic reagents and alkoxycarbonylation and deoxygenation reactions. The combination of palladium-catalysed coupling of 2 together with 1-alkynes/6-endo-dig annulation reactions in the presence of ammonia leads to functionalised pyrido[3,4-c]thiazoles in satisfactory yields. The utilisation of uncatalysed displacement reactions of the triflate group represents a very simple method for the synthesis of 4-N-,4-O-, and 4-S-substituted thiazoles.

Study of reactions between 1,2-diaza-1,3-butadienes and N,N′-diaryl- or N,N′-dialkylthioureas

1,2-Diaza-1,3-butadienes react with N,N′-diarylthioureas to give 2-(arylimino)-2,3-dihydrothiazole derivatives, whereas with N,N′-dialkylthioureas to afford 5,5-disubstituted 3-alkyl-2-(alkylimino)-thiazolidin-4-one derivatives. Under basic conditions, these last products surprisingly give rise to 2-thioxo-1,3,7-triazaspiro[4.4]non-8-en-4-one and 5-oxo-4-(4-substituted 5-oxo-2-thioxoimidazolidin-4-yl)-2,5-dihydro-1H-pyrazole derivatives. In acidic medium, 5,5-disubstituted 3-alkyl-2-(alkylimino)-thiazolidin-4-ones are converted into 2-(alkylimino)-1-thia-3,7-diazaspiro[4.4]non-8-en-4-ones. X-Ray crystal structures of two products were determined.