Selenium-promoted electrophilic cyclization of arylpropiolamides: synthesis of 3-organoselenyl spiro[4,5]trienones

Abstract

A synthetic approach to regioselective synthesis of 3-organochalcogenyl spiro[4,5]trienones and 3-organochalcogenyl[4,5]triene-2,6-diones is described through the reaction of arylpropiolamides with an electrophilic chalcogen source.

Transition Metal‐Free Synthesis of Carbo‐ and Heterocycles via Reaction of Alkynes with Organylchalcogenides

“…The selenium-promoted electrophilic cyclization of N-arylpropiolamides containing a methoxy group at 2-or 4-position of the aryl ring was reported by our research group as an efficient way to produce 3-selenyl-spiro [4,5]trienones 51 and 52 via a 5-endo-dig ipso mode (Scheme 28). [49] The best reaction conditions were achieved using 1.3 equiv. of the electrophilic source (PhSeBr) in MeNO 2 under nitrogen atmosphere at 90 °C.…”

Unexpected Substituent Effects in Spiro-Compound Formation: Steering N-Aryl Propynamides and DMSO toward Site-Specific Sulfination in Quinolin-2-ones or Spiro[4,5]trienones

“…For substrates bearing a para -methoxy or para -trifluoromethoxy groups, the carbonyl oxygen in the final product 3a might come from the OMe or OCF 3 groups substituted therein. 24 …”

“…On the basis of our experimental results, previous reports, ,,,, and wB97XD/6-311+G­(d,p) calculations, we propose substituent-dependent mechanistic pathways for the construction of 3-methylthioquinolin-2-one and 3-methylthiospiro[4.5]­trienone skeletons, respectively (Scheme ). We will discuss these in detail for three different substituents, R = para -H, para -F, and para -OMe, as they represent the various classes of substituents for which different reactivities have been observed.…”

“…This result is indeed in line with the idea that DMSO is the oxygen source when the para position of aniline was substituted with a F atom. For substrates bearing a para -methoxy or para -trifluoromethoxy groups, the carbonyl oxygen in the final product 3a might come from the OMe or OCF 3 groups substituted therein …”

Metal-Free Selenizative spiro-Tricyclization of N-Hydroxylethyl-N-arylpropiolamides

“…It seems possible that the treatment of electrophilic selenide A-2 with KHSO 4 provides A-1. The resulting electrophilic selenide species activates substrates 1, and electrophilic ipso-cyclization [16] takes place to release spiro-bicyclic cation B. This is trapped by the intramolecular hydroxyl group to give the final products 3.…”