Palladium-Catalyzed Direct C–H Arylation of Cyclic Enaminones with Aryl Iodides

Abstract

A ligand-free method for the Pd-catalyzed direct arylation of cyclic enaminones using aryl iodides was developed. This method can be applied to a wide range of cyclic enaminones and aryl iodides with excellent C5-regioselectivity. Using widely available aryl iodides, the generality of this transformation provides easy access to a variety of 3-arylpiperidine structural motifs.

Biomimetic Aerobic CH Olefination of Cyclic Enaminones at Room Temperature: Development toward the Synthesis of 1,3,5‐Trisubstituted Benzenes

“…The reason behind this observation is yet to be elucidated. As we reported before, [7, 18] N -phenylenaminone is a less effective substrate possibly due to its attenuated nucleophilicity. Indeed, it afforded a lower yield (32%, 18 ) compared to the N -benzyl analogue (57%, 17 ).…”

“…It is worth mentioning that the N -H enaminone, N -Cbz enaminone, and E -enaminone were again all incompatible under the current aerobic conditions ( 19 – 21 ), albeit consistent with our previous studies. [18-19] Our attempts on the uracil scaffold ( 22 ) were unfortunately not successful either. Nonetheless, we have devised a greener and milder method to alkenylate cyclic enaminones with comparable yields to our first protocol.…”

Novel 2‐Arylbenzothiazoles: Selective Chromogenic and Fluorescent Probes for the Detection of Picric Acid

“…Many synthetic protocols have been developed for the condensation of 2-aminobenzenethiol with different precursors such as carboxylic acids, [43] esters, [44] nitriles, [45] alcohols, [46] aldehydes, [47] aryl ketones, [48] etc for the synthesis of 2-arylbenzothiazoles. Most of the transformations require the use of metal catalysts, [45,[49][50][51][52][53][54] high temperature, longer reaction hours and limited substrate scope. Even the presence of trace amount of catalysts containing metal complex along with any other toxic reagent in biologically active precursors can cause severe health problems as 2-arylbenzothiazoles are also useful for blocking neurotransmission and as neuroprotective agents.…”

Regioselective C5-alkylation and C5-methylcarbamate formation of 2,3-dihydro-4-pyridones and C3-alkylation and C3-methylcarbamate formation of 4-(pyrrolidin-1-yl)furan-2(5H)-one

“…3,4 In the context of this research, we have investigated the Pd +2 -catalyzed C5 arylation (Suzuki and Hiyama cross coupling reactions) and C5 alkenylation (Fujiwara-Moritani) of 2,3-dihydro-4-pyridones as an effective strategy for the preparation of diverse structural motifs and complex molecules. 5-8 However, attempts to perform Pd +2 -catalyzed introduction of an sp 3 -hybridized group at C5 did not succeed, 5 presumably due to β-hydride elimination taking place after palladation but prior to the desired sequence of transmetalation and reductive elimination. 9 Therefore, other methods need to be discovered to affect these types of transformation, such as the direct, transition metal free C5 trifluoromethylation that was recently reported by us.…”