Pd-catalyzed carbonylation of α-arylvinyl bromides: Synthesis of 2-arylacrylic esters

Stereoselective synthesis of (E)-3,3-diaryl and (E)-3-aryl-3-aryloxy allylamines and allylalcohols from trans-cinnamyl chloride and alcohol

“…In previous works, we have used the dehydrobromination of (1,2-dibromoethyl)benzene in order to obtain the a-bromostyrene with regioselectivities up to 95%. 25,26 Here we have used the same simple KOH-promoted dehydrobromination protocol and were delighted to see that for the dibromides 4a and 4b, only the a-bromo regioisomers were observed and that for 4c, a 90 : 10 regioisomeric ratio was obtained. It is important to mention that the dehydrobromination reaction does not require high temperatures, microwave irradiation, ionic liquid as media or metal additives.…”

Synthesis of 2‐Arylacrylates from Pyruvate by Tosylhydrazide‐Promoted Pd‐Catalyzed Coupling with Aryl Halides

“…[10] While the classical method for the synthesis of 2-arylacrylates is the condensation of the corresponding arylacetate with paraformaldehyde, [11,12] more recently, these systems have been prepared through different Pd-catalyzed crosscoupling reactions: Suzuki cross-couplings with 2-chloracrylates, [13] and alkenyl boronates, [14] Negishi reaction with 2-metallated acrylates, [15] and Pd-catalyzed carbonylation of arylvinyl bromides. [16] In a very recent contribution, Wang et al reported a new synthesis of 2-arylacrylates by Pd-catalyzed coupling between diazoesters and arylboronic acids. [17] Herein, we present a new Pd-catalyzed cross-coupling approach to these systems that employs the tosylhydrazone of ethyl pyruvate as nucleophilic component, and therefore obviates the need for a stoichiometric organometallic reagent.…”

Synthesis of Tri- and Tetrasubstituted Olefins by Palladium Cross-Coupling Reaction

“…4 We have also shown that 1,2-(dibromoethyl)arenes, easily obtained from the bromination of the corresponding styrene derivatives, can be transformed into 2-arylacrylic esters by a one-pot dehydrobromination-carbonylation sequence. 5 The use of styrene in this reaction is an advantage over the traditional carbonylation of expensive and less available alkynes. The latter are also the starting material for most of the palladium-catalyzed syntheses of tri-and tetrasubstituted olefins.…”

“…6 Bromination of the stilbene at 0°C using CH 2 Cl 2 as solvent gave the 1,2-dibromo-1,2-diphenylethane in 71%, that underwent dehydrobromination (K 2 CO 3 as base in a 1:1 mixture of THF-MeOH at r.t.) furnishing the (E)-bromostilbene in 70-88% yield and 97-99% regioselectivity. 5 An initial screening was performed in order to determine the best conditions for the Pd-catalyzed Suzuki cross-coupling of (E)-bromostilbene with 4-methoxyphenylboronic acid. We have found similar results to those obtained for the coupling of arylboronic acids with vinyl bromide, generated in situ from 1,2-dibromoethane: Pd(OAc) 2 /PPh 3 as catalyst precursor, KOH as base, and a solvent mixture (MeOH-THF).…”

“…Under these conditions, the reaction proceeds smoothly and the (E)-1-aryl-1,2-diphenylethylenes were isolated in high yields. Long reaction times were necessary for the coupling with arylboronic acids containing electron-withdrawing groups ( Table 1, entries [5][6][7][8]. The regioselectivity was maintained in the cross-coupling reaction since it was the same as that observed for the starting stilbene (95-98%).…”