1,2,3-Thiadiazoles

Catalytic (3 + 2) umpolung annulations of α-thioacyl carbenes with aryl isothiocyanates

“…The catalytic (3 + n ) annulations of α-thioacyl carbenes, derived from 1,2,3-thiadiazoles under Rh( i ) or Ir( i ) catalysis, have served as an efficient tool for constructing thiacycles. 1–6 The advances in annulations with substrates containing C–X (X = heteroatom) multiple bonds indicated that the reactivity of α-thioacyl carbenes differed significantly as the electronic properties of substrates changed. 4–6 For example, in their (3 + 2) annulations with 1-phosphaalkynes, 4 α-thioacyl carbenes showed normal reactivity (nucleophilic sulfur and electrophilic carbenic carbon).…”

“…4–6 For example, in their (3 + 2) annulations with 1-phosphaalkynes, 4 α-thioacyl carbenes showed normal reactivity (nucleophilic sulfur and electrophilic carbenic carbon). 1,2 However, when nitriles were reacted, 3 b , c ,5 c complete umpolung reactivity (electrophilic sulfur and nucleophilic carbenic carbon) was observed. Additionally, semi-umpolung (nucleophilic sulfur and nucleophilic carbenic carbon) was probed in our formal (3 + 3) annulations with alkenyl and alkynyl aldehydes.…”

Cycloaddition reactions of heterocyclic azides with 2-cyanoacetamidines as a new route to C,N-diheteroarylcarbamidines

“…It is known that the cycloaddition reaction of azidopyrimidinediones with enamines [13] represents an effective method for the synthesis of pyrimidinyl amidines [14] (Scheme 1A). A few years ago, we discovered that the replacement of enamines with 2-cyano-N,N-dialkylethanethioamides in this reaction [15] led to the formation of amidines containing two heterocycles: pyrimidine-2,4-dione and 1,2,3-thiadiazole (Scheme 1B).…”

Recent Advances in the Synthesis of 5‐MemberedN‐Heterocycles via Rhodium Catalysed Cascade Reactions

“…1,2,3‐Triazoles have recently drawn remarkable attraction for its applications in medicine, analytical chemistry, agriculture, and material science [11a,b] . Benzo‐fused 1,2,3‐triazoles has abilities to undergo various catalytic or photolytic denitrogenative transformations [11c–f] . A wide variety of heterocyclic skeletons were afforded when metallocarbenes formed via transition metal catalyzed transannulation of 1,2,3‐triazole derivatives react with unsaturated compounds like alkynes, nitriles, imines, and other [11g–l] .…”