Ligand‐free palladium‐catalyzed tandem pathways for the synthesis of 4,4‐diarylbutanones and 4,4‐diaryl‐3‐butenones under microwave conditions

Abstract

Two efficient Pd‐catalyzed tandem pathways for the synthesis of 4,4‐diaryl‐2‐butanones and 4,4‐diaryl‐3‐buten‐2‐ones were elaborated. The first step in both procedures was the Heck coupling of methyl vinyl ketone (MVK) and various aryl iodides leading to 4‐aryl‐3‐buten‐2‐one with the yield of up to 92% in 1 hr. The second step performed with the same catalyst and a new portion of aryl iodide in the presence K2CO3 as a base produced 4,4‐diaryl‐3‐buten‐2‐ones in high yield. Reaction selectivity changed completely to saturated 4,4‐diaryl‐2‐butanones, reductive Heck products, when a tertiary amine was used instead of K2CO3. Due to the application of microwave irradiation (MW), the desired products were obtained in high yield in a short time (4 hr), using 0.5 mol% of the Pd (OAc)2 catalyst without additional ligands.

The Heck synthesis of β‐arylated ketones catalyzed by palladium immobilized on functional polysiloxane microspheres

“…The system formed in situ with pol‐am gave 87% of 3R product, while with pol‐py 65% of 3R was formed. The result obtained in the presence of pol‐am was similar to that with Pd(OAc) 2 only (91% of 3R [ 39 ] ), while a lower yield was noted in the presence of pol‐py. Next, the possibility of recycling was studied, and again better results were obtained with the pol‐am support than with pol‐py (Table 2).…”

“…For comparison, in the homogeneous system with the Pd(OAc) 2 catalyst, very similar results were obtained, namely 91% of 3R was formed in 1 h. [ 39 ] Thus, the polymer did not reduce the catalytic performance of palladium.…”

“…[ 38 ] Further arylation to 4,4‐diaryl derivatives was also successfully performed. [ 39 ] These reactions were carried out in homogeneous systems in which the final products were isolated by extraction and the catalyst was not recycled. Continuing these studies, we decided to use in the coupling of 3‐buten‐2‐ol and 3‐buten‐2‐one with ArI immobilized palladium catalysts which can be easily separated from the reaction products and reused.…”

Recent Progress of Metal Nanoparticle Catalysts for C–C Bond Forming Reactions

“…The introduction of nitrogen-and phosphorus-based molecules is also of special interest, because they not only act as a stabilizer of metal NPs, but also as ligands, which enhance the catalytic activity of metal NPs. The metal NPs stabilized by small molecules were used not only as prepared ones, but also as in situ generated ones [343][344][345][346][347][348][349][350][351][352][353][354][355][356][357][358][359][360][361].…”