acetal 6a of triacetonamine (3a) by alkylation followed by hydrolysis of the acetal functionality or alternatively from the corresponding secondary alcohol 2,2,6,6-tetramethylpiperidin-4-ol (7a) by N-alkylation and subsequent oxidation to introduce the ketone unit. Direct alkylation of 3a was only possible by using highly reactivehalides such as allyl or benzyl bromide with low yields. Treatment of
Synthesis of Unexpected Bifunctionalized Thiazoles by Nucleophilic Attack on Allenyl Isothiocyanate
作者:Baker Jawabrah Al-Hourani、Frank Richter、Kai Vrobel、Klaus Banert、Marcus Korb、Tobias Rüffer、Bernhard Walfort、Heinrich Lang
DOI:10.1002/ejoc.201301851
日期:2014.5
reactivity is also seen with N-aminophthalimide. In the presence of azide salt, hydrazoic acid, or N,N-disubstituted hydroxylamines, however, allenyl isothiocyanate is converted into bifunctionalized thiazoles. We explain the formation of these products by nucleophilic addition at the isothiocyanato moiety followed by ring closure and an N–N or N–O cleavage reaction to generate short-lived 2-imino-5-methylidenethiazole
New examples of substituted thiazole derivatives carrying different heterocyclic ring systems at C-2 position were prepared via the reaction of several allenyl isothiocyanates with nucleophiles such as imidazoles, pyrazoles, benzimidazoles, indazole, 1,2,3-triazole, 1,2,4-triazole, and 1H-benzotriazole. Although these allenyl isothiocyanates are very reactive electrophiles and tend to polymerize, the
The product of a three‐component reaction (3‐CR) is formed only if all reagents, the allenyl isothiocyanate, the nucleophile NuH (sec. amine), and the electrophile E+ (Michael acceptor, aldehyde, etc.) are present at the same time; otherwise a simple thiazole is generated by tautomerism (~ H+).
Three different reports on the syntheses of isolable 1H-azirines 6, 15, and 21 were reinvestigated. Instead of the claimed heterocyclic product 6, the isomeric thiazole derivative 7 has been isolated now with nearly identical yield. In the case of the asserted bicyclic 1H-azirine 15, the corrected structure includes the isomeric 3-aminomaleimide moiety of 18. A mechanism to explain the formation of