Mechanistic Investigation of the Palladium-Catalyzed Decarboxylative Cyclization of γ-Methylidene-δ-valerolactones with Isocyanates: Kinetic Studies and Origin of the Site Selectivity in the Nucleophilic Attack at a (π-Allyl)palladium
of this selectivity is provided. The selectivity between 3 and 4 is also influenced by the nature of the nitrogen substituent on isocyanates 2, and more electron-rich substituents tend to give higher selectivity toward azaspiro[2.4]heptanones 4. These studies represent the first systematic investigation into the selectivity between terminal attack and central attack at (pi-allyl)palladium species by
Palladium-Catalyzed Synthesis of 4-Oxaspiro[2.4]heptanes via Central Attack of Oxygen Nucleophiles to π-Allylpalladium Intermediates
作者:Ryo Shintani、Tomoaki Ito、Tamio Hayashi
DOI:10.1021/ol300852v
日期:2012.5.4
cyclopropanation of γ-methylidene-δ-valerolactones with aromatic aldehydes has been developed to give 4-oxaspiro[2.4]heptanes with high selectivity. The site of nucleophilic attack to a π-allylpalladium intermediate has been controlled with a sterically demanding phosphine ligand. The course of the reaction is highly dependent on ligands and solvents, and selective formation of methylenetetrahydropyrans has
Synthesis of Nine-Membered Azlactones by Palladium-Catalyzed Ring-Expansion of γ-Methylidene-δ-valerolactones with Aziridines
作者:Ryo Shintani、Keiichi Ikehata、Tamio Hayashi
DOI:10.1021/jo2006158
日期:2011.6.3
A palladium-catalyzed formal [6 + 3] cyclization of gamma-methylidene-delta-valerolactones with aziridines has been developed to produce 1,4-oxazonan-9-ones, a class of nine-membered azlactones that are not easily accessible by existing methods. The products thus obtained can also be further functionalized with ease.
Palladium-Catalyzed Decarboxylative [4 + 3] Cyclization of γ-Methylidene-δ-valerolactones with 1,1-Dicyanocyclopropanes
A palladium-catalyzed decarboxylative [4 + 3] cyclization of gamma-methylidene-delta-valerolactones with 1,1-dicyanocyclopropanes has been developed to produce cycloheptane derivatives in a convergent manner. This method can be applied to the synthesis of azepanes by reacting with aziridines, and their asymmetric variants have also been described. In addition, selective ring-expansion reactions can be achieved for certain gamma-methylidene-delta-valerolactones to give nondecarboxylated nine-membered lactones.