Isoindolinones comprise an important class of medicinally active compounds. Herein we report a straightforward functionalization of the isoindolinones with aryl bromides (22 examples) using a Pd(OAc)2/NIXANTPHOS-based catalyst system. Additionally 3-aryl 3-hydroxy isoindolinone derivatives, which exhibit anti-tumor activity, can be accessed via a tandem reaction. Thus, when the arylation product is exposed to air under basic conditions, in situ oxidation takes place to install the 3-hydroxyl group. Furthermore, a tandem arylation/allylic substitution reaction is advanced in which both the arylation and allylic substitution are catalyzed by the same palladium catalyst. Finally, a tandem arylation/alkylation procedure is presented. These tandem reactions enable the synthesis of a variety of structurally diverse isoindolinone derivatives from common starting materials.
A formidable challenge at the forefront of organic synthesis is the control of chemoselectivity to enable the selective formation of diverse structural motifs from a readily available substrate class. Presented herein is a detailed study of chemoselectivity with palladium-based phosphine catalysts and readily available 2-B(pin)-substituted allylic acetates, benzoates, and carbonates. Depending on the choice of reagents, catalysts and reaction conditions, 2-B(pin)-substituted allylic acetates and derivatives can be steered into one of three reaction manifolds: allylic substitution, Suzuki-Miyaura cross-coupling, or elimination to form allenes, all with excellent chemoselectivity. The studies on chemoselectivity of Pd catalysts in their reactivity with boron-bearing allylic acetate derivatives led to the development of diverse and practical reactions with potential utility in synthetic organic chemistry.
The direct arylation of weakly acidic sp3–hybridized C–H bonds via deprotonated cross–coupling processes (DCCP) is a challenge. Herein, a Pd(NIXANTPHOS)-based catalyst for the mono arylation of 4-pyridylmethyl 2-aryl ethers to generate diarylated 4-pyridyl methyl ethers is introduced. Furthermore, under similar conditions, the diarylation of 4-pyridylmethyl ethers with aryl bromides has been developed. These methods enable the synthesis of new pyridine derivatives, which are common in medicinally active compounds and in application in materials science.
A simple one-pot synthesis of β-hydroxyallenamides is reported. This procedure entails chemo- and regioselective hydroboration of 3-en-1-ynyl-sulfonylamides with CyBH followed by homoallenylation of aldehydes to yield β-hydroxyallenamides (up to 94% yield and >20:1 dr). Controlled synthesis of up to three continuous stereochemical elements was realized. Density functional theory (DFT) calculations suggest a concerted Zimmerman-Traxler chair-like transition state. Initial results suggest that enantio- and diastereoselective synthesis of β-hydroxyallenamides with optically active hydroboration reagents is viable.
The allylic substitution of 2‐pinacolborane‐substituted allylic acetates (I) with nucleophiles (II) leads to boranes (III), which can be converted without isolation into ketones (IV) and trisubstituted alkenes (VI).
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