Reductive Ring Opening of Arylcyclopropanecarboxamides Accompanied by Borylation and Enolate Formation

Abstract

Treatment of arylcyclopropanecarboxamides with a sodium dispersion in the presence of methoxypinacolborane as a reduction-resistant electrophile leads to reductive cleavage of the cyclopropane ring followed by instant trapping with the boron electrophile to yield the enolates of γ-aryl-γ-borylalkanamides. The enolates react further with a different electrophile to yield the corresponding α-substituted amides with anti selectivity.

Substitution-Dependent Ring-Opening Hydrosilylation or Dehydrogenative Hydrosilylation of Cyclopropyl Aldehydes and Ketones Catalyzed by Au Nanoparticles

“…Our group has recently reported that the Au/TiO 2 -catalyzed silaboration of aryl-substituted cyclopropyl aldehydes gives acyclic β-boronate silyl enol ethers via ring-opening of the cyclopropane ring (Scheme ). A very similar ring-opening borylation concept with methoxypinacolborane has been reported more recently in the case of aryl cyclopropane carboxamides using Na metal as a one-electron donor . Given the facile activation of hydrosilanes on Au nanoparticles, which enables their addition on a variety of functional groups, in this manuscript, we report our studies regarding the reaction between cyclopropyl aldehydes or ketones with hydrosilanes using supported Au nanoparticles on titania (Au/TiO 2 ) as the catalyst.…”

“…14 A very similar ring-opening borylation concept with methoxypinacolborane has been reported more recently in the case of aryl cyclopropane carboxamides using Na metal as a one-electron donor. 15 Given the facile activation of hydrosilanes on Au nanoparticles, which enables their addition on a variety of functional groups, 16 in this manuscript, we report our studies regarding the reaction between cyclopropyl aldehydes or ketones with hydrosilanes using supported Au nanoparticles on titania (Au/TiO 2 ) as the catalyst. The question regarding this reaction is whether cyclopropyl C−C cleavage could be achieved or it would simply lead to the reduction of the carbonyl group.…”

Borylation of Alkenyl Carbamates by Means of Sodium Metal

“…When sodium dispersion was placed from the beginning, the yield of 2a was 47%, and 29% of 1a was recovered (entry 13), which resulted from the over-reduction of 2a and the resulting shortage of sodium dispersion as well as changes in particle size upon adding sodium dispersion in THF. 7f When sodium dispersion was added in 1 s, the yield of 2a was 52%, and 26% of 1a was recovered (entry 14) probably because of similar reasons. Too slow addition, over 5 min, also resulted in a lower yield and recovery of 1a (12%) (entry 15) although the reason is unclear.…”