The chemistry of acetylenic and allenic sulfones

Synthesis of new spin labels for Cu-free click conjugation

“…Because the chemical properties of stable free nitroxide radicals limit the range of reactions and procedures applicable, it was obvious that the 'clickable' (acetylene) part could not be formed on the nitroxide ring, but that the nitroxide should be attached to an appropriate acetylene moiety. We have explored two different strategies to promote the [3+2] cycloaddition under mild conditions: (1) use of an alkyne activated with an electron-80 withdrawing group, 14,15 and (2) use of a strained alkyne. 16 As far as we know, this is the first report of the synthesis and model reactions for azide specific, biocompatible spin label reagents.…”

Silver‐Catalyzed Rearrangement of Propargylic Sulfinates to Allenic Sulfones

“…[1] They have been used as precursors of enol ethers in the context of both carbanionaccelerated Claisen rearrangements and [4 + 3]-cycloaddition reactions. [2,3] They are reactive dienophiles, enophiles and dipolarophiles.…”

A Facile and Reliable Method for the Synthesis of Tetrabenzoporphyrin from 4,7‐Dihydroisoindole

“…Tosylacetylene is regarded as a powerful dienophile. [16] Analysis of the published data shows that tosylacetylene is largely employed in very facile reactions with highly reactive, electron-rich cyclic dienes, such as N-acylpyrroles, [15a,17] furan, [18] and cyclo-pentadienes [19] with only a few examples published on the cycloaddition to less reactive acyclic dienes with the use of rather drastic reaction conditions. [20] We could not achieve the cycloaddition of tosylacetylene to 1,3-butadiene when trying to perform the reaction in various solvents by heating in a thick-walled vessel.…”