Palladium-Catalyzed Dehydrative Cross-Coupling of Allylic Alcohols and N-Heterocycles Promoted by a Bicyclic Bridgehead Phosphoramidite Ligand and an Acid Additive

Abstract

A mild and efficient dehydrative cross-coupling reaction between allylic alcohols and N-heterocycles using palladium catalysis is reported. A bicyclic bridgehead phosphoramidite (briphos) ligand together with Pd(dba)2 is a highly efficient catalyst, and an acid additive involved in the rate-determining step promotes the catalytic cycle. The coupling reaction of allylic alcohols with N-heterocycles including imidazoles, benzimidazoles, and triazole proceeds under mild reaction conditions with high yields using Pd/briphos and pentafluorophenol.

Nickel-Catalyzed Suzuki Cross Couplings with Unprotected Allylic Alcohols Enabled by Bidentate N-Heterocyclic Carbene (NHC)/Phosphine Ligands

“…Thus, allylic carbonates, sulfonates, acetates, phosphonates, or halogens are typically employed in allylic functionalization reactions, which add undesirable synthetic steps . Recent advances in cross couplings with unprotected allylic alcohols have generally required the use of expensive noble-metal catalysts, such as iridium, ruthenium, rhodium, or palladium , (Figure ). Nickel, on the other hand, represents an ideal catalyst for these transformations, because of its relatively low cost and high abundance.…”

Atom-Economical Palladium Carbon-Catalyzed de Novo Synthesis of Trisubstituted Nicotinonitriles

“…Propargyl and allyl alcohols have emerged as highly effective candidates for metal-assisted transformations; however, to the best of our knowledge, they have not been explored to a satisfactory extent with respect to the synthesis of pyridine derivatives. Palladium catalysts are well-known activators of alkynes . Herein, we report a highly effective atom-economical palladium carbon-catalyzed synthesis of trisubstituted 3-cyano-pyridines or “nicotinonitriles” employing the easily available alkyl nitriles serving as both a solvent and a precursor.…”

“…Palladium catalysts are well-known activators of alkynes. 14 Herein, we report a highly effective atom-economical palladium carbon-catalyzed synthesis of trisubstituted 3-cyano-pyridines or "nicotinonitriles" employing the easily available alkyl nitriles serving as both a solvent and a precursor. The heterogeneous catalytic system delineates an easy breakthrough for this transformation.…”

Bimetallic Catalysis: Palladium/Lanthanide co‐Catalyzed Allylation of Anilines

“…[1] The source of the allyl moiety is usually an allyl ester or an allyl carbonate. As these compounds need to be formed in an additional step from allyl alcohol, there has been interest in using allyl alcohol directly in Tsuji-Trost chemistry.G iven the poor leaving-group ability of hydroxide, most approaches involve the addition of an acidic activator.E xamples of such activators include Ti(IV) complexes, [2] arsenic(V) oxide, [3] triethyl borane, [4] triethylaluminum, [5] stannous chloride, [6] benzoic acid, [7] threonine derivatives [8] and pentafluorophenol, [9] as wella sh ydrogen bond donors. [10] In an inventive contribution, CO 2 has been used for in situ carbonate formation.…”

“…[18] The presence of methylg roups in the ortho position had as eriously deleterious effect on the yield (entries 6a nd 7). Electron-withdrawing groups,i ncluding halogens, also resulted in low or no yields (entries [8][9][10][11][12]. Use of ahigher boiling solvent, di-n-butyle ther,resulted in rapid catalyst decomposition.…”