Enantioselective palladium/copper-catalyzed C–C σ-bond activation synergized with Sonogashira-type C(sp³)–C(sp) cross-coupling alkynylation

Abstract

A highly enantioselective Pd/Cu-catalyzed tandem C–C bond activation/Sonogashira reaction was developed with the aid of new TFSi-Phos, which provided chiral alkynyl indanones in good yields and enantioselectivities.

Synthesis and characterization of lignin–poly(acrylamide)–poly(2‐methacryloyloxyethyl) trimethyl ammonium chloride copolymer

“…In addition, the methyl (CH 3 ) group connected to ammonium group in DMC was indicated by the peak at 0.8 ppm. The small peak for KL segment was also presented at 7.2 ppm spectrum of KL–AM–DMC copolymer . These peaks indicate that both AM and DMC participated in the copolymerization of KL, AM, and DMC …”

“…The dried and dialyzed precipitates and supernatants of the reaction products conducted under the conditions of 2 h, 0.11 mmol of initiator, 0.011 mol of KL, 0.028 mol of AM, 0.024 of DMC, pH 4.0, and 80 °C were analyzed by NMR and presented in Figure . As shown in KL spectrum (i.e., raw material), the peak at 8.5 ppm is attributed to unsubstituted phenolic protons; at 7.42–5.99 ppm is attributed to aromatic protons; at 4.5–3.05 ppm is attributed to protons in methoxyl groups of lignin; at 3.6– 3.2 ppm is assigned to the methylene protons in β–β structure; and at 3.3–1.75 ppm is assigned to the aliphatic protons in lignin . Peaks appearing at 4.7 ppm is assigned to the solvent of D 2 O.…”

“…The sample that was produced under the optimal conditions of 0.011 mol of KL, 0.024 mol of DMC, 0.028 mol of AM, 80 °C, 2 h, and the initiator dosage of 0.11 mmol was selected as the best sample. The broad band around 3400 cm −1 was assigned to the OH stretching absorption in the phenolic and aliphatic compounds of KL . The CH vibration absorption band of the aromatic ring appeared at 1590, 1510, and 1448 cm −1 , which represent the existence of the aromatic skeletal structure in KL and KL–AM–DMC .…”

Synergistic Pd/Cu Catalysis in Organic Synthesis

“…Recently, Xu and co‐workers utilized the tension of four‐membered rings to accomplish an enantioselective tandem C−C σ‐bond activation/Sonogashira‐type alkynylation of cyclobutanones with terminal alkynes (Scheme ) . Ligand screening suggested that bidentate ligands were not compatible with this reaction and bulky monodentate ligands gave better yields and enantioselectivity.…”

Enantioselective Difunctionalization of Alkenes by a Palladium‐Catalyzed Heck/Sonogashira Sequence

“…Alternatively, cross‐couplings of in situ generated σ‐alkyl Pd II intermediates instead of alkyl halides with terminal alkynes have emerged as an elegant strategy for the synthesis of racemic alkyl‐substituted internal alkynes . Recently, the groups of Jia and Xu developed an enantioselective Pd‐catalyzed dearomative Heck/Sonogashira coupling of indoles and a Pd/Cu‐catalyzed alkynylation of cyclobutanones to give chiral alkyl‐substituted internal alkynes. However, to the best of our knowledge, the development of highly enantioselective intramolecular Heck/Sonogashira reactions of alkenes with terminal alkynes has met with less success and is still in great demand…”