Cycloaddition Reactions of 1,3-Diaza-2-azoniaallene Salts and Glycals

Synthesis of Highly Stable 1,3-Diaryl-1H-1,2,3-triazol-5-ylidenes and Their Applications in Ruthenium-Catalyzed Olefin Metathesis

“…Trimethylsilyl alkynes participate in this reaction as terminal alkyne surrogates, since protodesilylation occurs readily and the protic triazolium salts are instead obtained ( C aa (H + ) , C ae (H + ) , C ai (H + ) ). As indicated by Wirschun and Jochims, success in the formation of the heterocycle probably depends on the stability of G and H . For some combinations of triazene and alkyne substrates, we found that the reaction proceeds best at high concentrations in the presence of an excess of alkyne.…”

“…Evidently, these target precursors, unlike 3-alkyltriazolium salts C a - d (H + ) , are not accessible from the direct arylation of triazoles at N3. However, Wirschun and Jochims reported the preparation in moderate to good yields of a number of 1,3-diarylated-1 H -1,2,3-triazolium salts C Ar (H + ) by the formal 1,3-dipolar cycloaddition between 1,3-diaza-2-azoniaallene salts H and alkynes or synthetic alkyne equivalents (Scheme ). , …”

C2-Amidoglycosylation. Scope and Mechanism of Nitrogen Transfer

“…Over the last few decades, a variety of methods have been developed for the nitrogen ([ N ]) transfer to glycals ( 1 → 2 , Scheme ). In this context, numerous N -functionalities have been introduced at the C2 -position including oxidized precursors to amines, such as azide, hydrazine, triazene, or the nitro group, as well as protected amino-functionalities such as amides, carbamates, sulfonamides, or phosphoramides . However, the majority of naturally occurring C2 -azasugars are N -acetylated, and this highlights the importance of this class of carbohydrate residue in glycoconjugate synthesis.…”