5720-06-9Relevant articles and documents
Asymmetric 1,4-Addition of Arylboronic Acids to β,γ-Unsaturated α-Ketoesters using Heterogeneous Chiral Metal Nanoparticle Systems
Miyamura, Hiroyuki,Yasukawa, Tomohiro,Zhu, Zhiyuan,Kobayashi, Shū
supporting information, p. 353 - 359 (2019/12/15)
Asymmetric 1,4-addition reactions with β,γ-unsaturated α-ketoesters are valuable because the resulting chiral ketoester compounds can be converted into various useful species that are often used as chiral building blocks in drug and natural product synthesis. However, β,γ-unsaturated α-ketoesters have two reactive points in terms of nucleophilic additions, which will lead to the 1,4-adduct, the 1,2-adduct and to the combined 1,4- and 1,2-adduct. Therefore, controlling this chemoselectivity is an important factor for the development of these transformations. Here, we developed an asymmetric 1,4-addition of aryl boronic acids to β,γ-unsaturated α-ketoesters by using heterogeneous chiral rhodium nanoparticle systems with a chiral diene ligand bearing a secondary amide moiety. The newly developed polydimethylsilane-immobilized rhodium nanoparticle catalysts showed high activity, high chemoselectivity, and excellent enantioselectivity, and this is the first heterogeneous catalytic system for this asymmetric reaction. Metal nanoparticle catalysts were recovered and reused without loss of activity or leaching of metal. (Figure presented.).
Chemoselective Rhodium-Catalyzed Borylation of Bromoiodoarenes under Mild Conditions
Varni, Anthony J.,Bautista, Michael V.,Noonan, Kevin J.T.
, p. 6770 - 6777 (2020/07/21)
A chemoselective rhodium-catalyzed borylation has been developed for the preparation of aryl boronate esters. The reaction proceeds under mild conditions with excellent selectivity for C-I bonds in bromoiodoarenes and exhibits broad functional group tolerance. This procedure can act as a complementary approach toward bifunctional arenes along with other metal-catalyzed borylations. Additionally, the reaction's utility in the preparation of monomers for metal-catalyzed cross-coupling polymerization is demonstrated.
Bedford-type palladacycle-catalyzed miyaura borylation of aryl halides with tetrahydroxydiboron in water
Zernickel, Anna,Du, Weiyuan,Ghorpade, Seema A.,Sawant, Dinesh N.,Makki, Arwa A.,Sekar, Nagaiyan,Eppinger, J?rg
, p. 1842 - 1851 (2018/02/23)
A mild aqueous protocol for palladium catalyzed Miyaura borylation of aryl iodides, aryl bromides and aryl chlorides with tetrahydroxydiboron (BBA) as a borylating agent is developed. The developed methodology requires low catalyst loading of Bedford-type palladacycle catalyst (0.05 mol %) and works best under mild reaction conditions at 40 °C in short time of 6 h in water. In addition, our studies show that for Miyaura borylation using BBA in aqueous condition, maintaining a neutral reaction pH is very important for reproducibility and higher yields of corresponding borylated products. Moreover, our protocol is applicable for a broad range of aryl halides, corresponding borylated products are obtained in excellent yields up to 93% with 29 examples demonstrating its broad utility and functional group tolerance.