Facile synthesis of fused 1,2,3-triazoles by a proline-catalyzedreaction of an azido aldehyde and a nitroalkane is elaborated. The present tandem protocol proceeds via an organocatalytic Knoevenagelcondensation of the azido aldehyde and nitroalkane followed by intramolecular azide–nitroalkene cycloaddition. The functionalized bicyclic triazole is obtained by elimination of HNO2 from the cycloadduct
Synthesis of fused 1,2,4-thiadiazolines by intramolecular cycloaddition-elimination reactions of 4-methyl-5-(cyano tethered)imino-Δ2-1,2,3,4-thiatriazolines
作者:Gerrit L'abbé、Stefan Leurs
DOI:10.1016/s0040-4020(01)90364-3
日期:1992.9
A series of 5-imino-1,2,3,4-thiatriazolines, bearing a cyano tether at the iminefunction, were prepared and converted into fused 1,2,4-thiadiazole derivatives by thermolysis; these are 12a → 13, 20a → 21, 20b → 22 and 29 → 30 (Schemes 2–5). In one case, the precursor thiatriazole also underwent an intramolecular cycloaddition-elimination reaction to give a fused 1,2,4-thiadiazole; namely 17a → 18
development of expeditious methods to synthesize these skeletons remains a challenging task. In this work, the catalyticcyclization of biomass-derived 2-furylcarbinols with an azide to form fused triazoles is described. This approach takes advantage of a single catalyst Yb(OTf)3 and operates via a furfuryl-cation-induced intramolecular [3 + 2] cycloaddition/furan ring-opening cascade.
Iridium-Catalyzed C–H Amination/Cyclization for Medium to Large <i>N</i>-Heterocycle-Fused Dihydroquinazolinones
作者:Tao Zhang、Xunqing Dong、Hitesh B. Jalani、Jiaqi Zou、Guigen Li、Hongjian Lu
DOI:10.1021/acs.orglett.9b01167
日期:2019.5.17
A practical iridium-catalyzed cascade/stepwise synthesis of dihydroquinazolinones (DHQs) and bis-DHQs fused to medium to large N-heterocyclic rings is developed. The reaction undergoes benzamide-directed intermolecular C–H amination with an aldehyde-tethered alkyl azide, and then the newly installed amino group undergoes intramolecular cyclization with a remote aldehyde group present in azide and amidyl