Department of Chemistry, School of Chemical and Biotechnology, SASTRA Deemed University, Thanjavur-613401, Tamil Nadu, India.
Department of Chemistry, National Institute of Technology, Warangal, Warangal-506004, Telangana, India.
Org Biomol Chem. 2020 Nov 7;18(41):8474-8485. doi: 10.1039/d0ob01840f. Epub 2020 Oct 16.
Palladium(ii)-catalyzed regioselective syn-chloropalladation and anti-acetoxypalladation-initiated cascade processes were developed for the synthesis of functionalized tetrahydroquinolines. A series of N-propargyl arylamines tethered with an α,β-unsaturated carbonyl scaffold underwent atom economical cascade reactions to deliver chloro- and acetoxy-substituted tetrahydroquinolines bearing an exocyclic double bond in high yields. A mechanism is proposed for these cascade processes involving a sequential syn-chloropalladation or anti-acetoxypalladation of alkynes followed by intramolecular olefin insertion (6-exo-trig) and protonolysis steps. The reaction was completely regioselective and the terminal aryl/alkyl group of the propargyl moiety dictated the regiochemistry of the initial nucleopalladation. The role of the bidentate nitrogen ligand is crucial to trigger the acetoxypalladation-initiated cascade sequence in contrast to the chloropalladation-initiated process.
钯（II）催化的区域选择性顺式氯钯化和反式乙酰氧钯化引发的级联反应被开发用于合成功能化的四氢喹啉。一系列带有α,β-不饱和羰基支架的 N-炔丙基芳胺经历了原子经济性的级联反应，以高产率得到了带有外环双键的氯代和乙酰氧基取代的四氢喹啉。提出了一种涉及炔烃的顺序顺式氯钯化或反式乙酰氧钯化，随后进行分子内烯烃插入（6-endo-trig）和质子裂解步骤的级联反应机制。该反应具有完全的区域选择性，炔丙基部分的末端芳基/烷基决定了初始亲核钯化的区域化学。双齿氮配体的作用对于引发乙酰氧钯化引发的级联序列至关重要，而不是氯钯化引发的过程。
