Ring Transformations of Five-Membered Heterocycles

The trans–cis and the azide–tetrazole ring-chain isomerization of 2-azido-1,3-azoles: Quantum chemical study

“…Therefore, ring-chain isomerism is an important aspect of organic chemistry [2][3][4][5][6][7][8][9][10][11][12][13][14].…”

Fluorinated heterocyclic compounds: an assay on the photochemistry of some fluorinated 1-oxa-2-azoles: an expedient route to fluorinated heterocycles

“…In this context, heterocyclic rearrangements [8][9][10][11][12][13] and, among them, photoinduced rearrangements [14][15][16][17] of O-N bond containing azoles [18][19][20][21][22][23] appear to be a promising strategy for the synthesis of target compounds. In this context, we recently reported [24] the synthesis of 3-amino-(or 3-N-alkylamino-)-5-perfluoroalkyl-1,2,4-oxadiazoles (2) by photolysis of some 3-perfluoroalkanoylamino-4-phenyl-1,2,5-oxadiazoles (furazans) (1) at l ¼ 313 nm in methanol and ammonia or primary aliphatic amines (Scheme 1).…”

Three‐Component Assembly and Divergent Ring‐Expansion Cascades of Functionalized 2‐Iminooxetanes

“…[2] Intrigued by their potential synthetic applications, especially those based on a ring-opening process, we therefore focused our efforts on the construction of electrondeficient 2-iminooxetanes. [3,4] Herein, we present a novel copper(I)-catalyzed three-component reaction to produce functionalized N-sulfonyl-2-iminooxetanes 5 by a [2 + 2] cycloaddition of aromatic 2-oxobut-3-ynoates 2 with N-sulfonylketenimines I generated in situ. [5,6] These 2-iminooxetanes 5 are well-established substrates for selective rearrangement to functionalized pyrrolidinones 3 or maleimides 4 through a divergent ring-expansion cascade reaction (Scheme 1).…”