On the Regiochemistry of Nucleophilic Attack on 2-Halo π-Allyl Complexes. 4. The Effect of Silver Acetate and Nucleophile Concentrations in Competitive Nucleophilic Attack with Malonate and Phenoxide Nucleophiles

Abstract

2,3-Dibromo-1-propene or its allyl carbonate analogue are ionized under Pd catalysis to generate the 2-bromo Pd-pi-allyl complex (triphenylphosphine ligand), which alkylates with malonate nucleophile at the terminal position. The presence of acetate ion in the reaction mixture results in some malonate attack being redirected to the central carbon. The acetate ion can come from the ionization of 1-acetoxy-2-bromo-2-propene or by the addition of silver acetate to the reaction mixture. The addition of phenoxide ion to the reaction also causes the same regiochemical phenomena, although harder anions such as methoxide exert no such effect.

C(sp3)O Bond‐Forming Reductive Elimination of Ethers from Bisphosphine‐Ligated Benzylpalladium(II) Aryloxide Complexes

“…Reactions that occur by dissociation of aryloxide ligands to form ionic intermediates during organometallic processes in nonpolar solvents are unusual. Nucleophilic attack of phenoxide onto a π‐bound allyl ligand is known,23–26 but none of the reported reactions begin with an allylalkoxide complex. …”

Palladium-Catalyzed Double Alkylation of 3-Aryl-2-fluoroallyl Esters with Malonate Nucleophiles through the Carbon–Fluorine Bond Cleavage

“…On the other hand, as an alternative reaction process, nucleophilic attack at the central carbon atom of the π-allyl moiety provides cyclopropane derivatives under the appropriate reaction conditions . Furthermore, three groups have discovered that the disubstituted products, in which nucleophiles attack both the terminal and central carbon atoms of the π-allyl palladium complex, were obtained from the reaction of 2-haloallyl compounds. − In 1995, Bäckvall reported the double alkylation of the 2-chloro-π-allyl palladium complex with sodium dialkyl methylmalonate . The palladium-catalyzed double etherification of 2,3-dibromo-1-propene with sodium phenoxide was demonstrated by Organ’s group in 1997 .…”

“…Furthermore, three groups have discovered that the disubstituted products, in which nucleophiles attack both the terminal and central carbon atoms of the π-allyl palladium complex, were obtained from the reaction of 2-haloallyl compounds. − In 1995, Bäckvall reported the double alkylation of the 2-chloro-π-allyl palladium complex with sodium dialkyl methylmalonate . The palladium-catalyzed double etherification of 2,3-dibromo-1-propene with sodium phenoxide was demonstrated by Organ’s group in 1997 . They further succeeded in obtaining the doubly alkylated product as a major product from the reaction with malonate nucleophile, but the reaction required a catalytic amount of phenoxide and detectable amount of doubly substituted products by both the malonate and phenoxide anions.…”

“…To our delight, the highest yield (86% NMR yield, 90% isolated yield) was obtained by the combination of [Pd(C 3 H 5 )(cod)]BF 4 with bpy (entry 11). The exact structure, including olefin geometry, of product ( E )- 3aa was determined by an X-ray crystallographic analysis (Figure ). , We also examined the reaction using [Pd(C 3 H 5 )(cod)]BF 4 /tmeda ( N , N , N ′, N ′-tetramethylethylenediamine) or Pd(dppp) 2 , but both catalysts gave a mixture of 3aa and 4aa with low yields (entries 12 and 13). We further confirmed that the reaction of 2-chlorocinnamyl acetates ( 5 ) provide 7aa as a major product and the reaction of 2-bromocinnamyl acetates ( 6 ) did not gave any doubly alkylated product 3aa under optimized conditions (Scheme ) .…”

C(sp3)O Bond‐Forming Reductive Elimination of Ethers from Bisphosphine‐Ligated Benzylpalladium(II) Aryloxide Complexes

“…Reactions that occur by dissociation of aryloxide ligands to form ionic intermediates during organometallic processes in nonpolar solvents are unusual. Nucleophilic attack of phenoxide onto a p-bound allyl ligand is known, [23][24][25][26] but none of the reported reactions begin with an allylalkoxide complex.…”