A combined experimental and computational study of NHC-catalyzed allylation of allenoate with MBH esters: new regiospecific and stereoselective access to 1,5-enyne

Abstract

An NHC-catalyzed regiospecific allylation of α-substituted allenoates with MBH carbonates derived from aryl aldehyde furnished highly functionalized 1,5-enynes.

NHC-Catalyzed [2 + 4] Annulation of Alkynyl Ester with Chalcone

“…Since the electronic nature of alkynyl esters was similar to that of allenoates, we envisioned that the NHC-catalyzed transformations of alkynyl esters should also display unique chemoselectivities, compared with those accelerated by phosphine or tertiary amines. As a continuation of our work on the NHC-catalyzed transformations, we herein report our preliminary results of NHC-catalyzed [2 + 4] cycloaddition of alkynyl ester with chalcone (Scheme ).…”

Squaramide-catalyzed asymmetric regioselective allylic alkylation of 4-aminopyrazolones with Morita–Baylis–Hillman carbonates

“…In addition, the S N 2′–S N 2 process is depicted in pathway B. 12 b ,14 The catalyst C8 reacts with the isatin-derived MBH carbonate 4a in an S N 2′ process to yield intermediate C , which was engaged in the substitution reaction with deprotonated 4-aminopyrazolone 1a . In TS 3 , the hydrogen bonding interactions between the squaramide moiety of the bifunctional catalyst and the substrate 1a facilitate the subsequent S N 2 substitution leading to products 5aa .…”

“…To the best of our knowledge, examples concerning the catalytic asymmetric versions of the S N 2′–S N 2 type process reported in the literature are rare. 12 b ,14 Herein, we report an asymmetric allylic alkylation of 4-aminopyrazolones 15 with various MBH carbonates with the aid of a bifunctional squaramide catalyst (Scheme 1d). This reaction afforded a range of pyrazolone derivatives bearing a nitrogen-containing quaternary stereocenter in high yields with excellent regioselectivities and enantioselectivities.…”

A DFT study on the mechanism and regioselectivity of NHC-catalyzed double acylation of aromatic 1,2-diketones with α,β-unsaturated ketones

“…The intermediate M 2 is a functional enamine, which is different from the Breslow intermediate with OH replaced by OG, and the detailed mechanism remains unclear and to be investigated in theory. To solve this issue and promoted by our continuous interest in NHC catalysis, [21][22][23][24][25][26][27][28][29][30][31][32] we selected the NHC-catalyzed double acylation reaction of aromatic 1,2-diketone (R1) with a,b-unsaturated ketone (R2) reported by the Takaki group 19 as the research object to study the detailed mechanism and regioselectivity.…”