Construction of heterocyclic rings from cyclopropenes

Abstract

Highly strained cyclopropenes are valuable functional building blocks in the construction of heterocyclic skeletons, which are highly appealing due to their wide and important applications in synthetic chemistry and medicinal...

Copper-catalyzed multicomponent assembly of γ-butenolides via the interception of carbonyl ylides with iminium ions

“…Cyclopropenes have earned a coveted spot in the repertoire of chemists due to their smallest ring size and high ring strain. 10 An array of interesting transformations toward vinyl carbenes generated from the C–C bond cleavage of cyclopropenes have consequently arisen, capitalizing on cycloisomerization, 11 cyclopropanation, 12 X–H insertion (X = C, O, Si, etc. ) 12 a ,13 and cross coupling reactions.…”

Heterocycles from cyclopropenones

“…2 In order to enable such methods, one can use C–C-strained, often cyclic, building blocks that are consequently spring-loaded for C–C bond activation. 3–22…”

Copper-Catalyzed Hydroamination: Enantioselective Addition of Pyrazoles to Cyclopropenes

“…An initial experiment with Cu in the absence of ligands resulted in the formation of allylic pyrazole 5a (Figure A). Achiral ligands, such as rac -BINAP, led to the exclusive formation of the same undesired isomer 5a , likely via a ring-opening pathway , involving N–H bond insertion into allylic carbene 5a′ . Using commercial (IPr)­CuCl offered high chemoselectivity to 3a (see the Supporting Information (SI)) .…”