Yuji Hanzawa

Metal-Free [2 + 2 + 1] Annulation of Alkynes, Nitriles, and Oxygen Atoms: Iodine(III)-Mediated Synthesis of Highly Substituted Oxazoles

The metal-free [2 + 2 + 1] annulation of alkynes, nitriles, and O-atoms for the regioselective assembly of 2,4-disubstituted and 2,4,5-trisubstituted oxazole compounds has been achieved by the use of PhIO with TfOH or Tf2NH. The present reaction could be applied to a facile synthesis of an anti-inflammatory drug.

Palladium-catalyzed reactions of acylzirconocene chloride with organic halides

Abstract Palladium-catalyzed reactions of nonanoylzirconocene chloride 1 with aryl halide, acid halides, and allylic halides gave the acylated compounds through a nucleophilic attack of an “unmasked” acyl anion in fair to excellent yields. In an analogous way, allylic acetate gave an acyl substituted product through the reaction of 1 .

Rh(I)-catalyzed addition of alkenylzirconocene chlorides to aldimine derivatives

Abstract [RhCl(COD)] 2 (2 mol%) catalyzed reactions of alkenylzirconocene chloride complexes to N -Ts, -PO(OEt) 2 and COOR aldimine derivatives were efficiently carried out in dioxane at room temperature to give allylic amine derivatives in excellent yields. This is the first example of the catalytic addition reactions of alkenylzirconocene chloride complexes to aldimine derivatives.

ACYLZIRCONOCENE CHLORIDE AS AN UNMASKED ACYL ANION

Under mild conditions the acyl group of acylzirconocene chloride 1 formed from an alkene or alkyne and [(C5 H5 )2 ZrHCl] reacts as an unmasked acyl anion. The Lewis acid mediated reactions with aldehydes that yield α-ketol products in high yields demonstrate the versatility of this reagent for C-C coupling.

Palladium-catalyzed acylation reactions of α,β-unsaturated ketones with acylzirconocene chloride: Remarkable control of 1,2- and 1,4-selectivity by the catalyst

Abstract Palladium-catalyzed reactions of α,β-unsaturated ketones with acylzirconocene chloride showed not only an efficient acyl transfer to α,β-unsaturated ketones but also a remarkable regiochemical control by selecting PdCl2(Ph3)2 or Pd(OAc)2.

Acylzirconocene Chloride as an "Unmasked" Acyl Anion: Enantioselective 1,2-Addition to alpha,beta-Unsaturated Ketone Derivatives.

The chiral monodentate phosphane ligand (R)-MOP facilitated the first enantioselective nucleophilic 1,2-addition of an unmasked acyl anion to a carbonyl group in the Pd(II)-catalyzed reaction of alpha,beta-unsaturated ketones with acylzirconocene chlorides [Eq. (1), 66 % ee, 88 % yield; (R)-MOP=(R)-2-(diphenylphosphanyl)-2-methoxy-1,1-binaphthyl].

Pd-catalyzed regioselective acylation of α, β-unsaturated ketone derivatives by acylzirconocene chloride as an acyl group donor

Abstract Acylzirconocene chlorides reacted with α,β-unsaturated ketones (α,β-enone or -ynone) to give regioselectively 1,2- or 1,4-products under Pd-catalyzed conditions. In the reactions of α,β-enones, excellent regioselectivity was attained by the choice of the Pd(II) catalyst system. Thus, the 1,2- or 1,4-products were selectively prepared by choosing PdCl2(PPh3)2 or Pd(OAc)2–BF3·OEt2, respectively. The presence of a monodentate phosphine ligand brought about a 1,2-addition product, selectively. In these Pd-catalyzed reactions, the Pd(0) species was considered to be an active catalyst, which was generated in situ through transmetalation of acyl groups from zirconium to Pd(II) followed by reductive elimination of Pd(0). α,β-Ynones also reacted with acylzirconocene chloride to give regioselectively 1,4-products under the Pd-catalyzed conditions. In contrast to the reactions of α,β-enones, the presence of a triphenylphosphine ligand brought about the selective formation of 1,4-adduct. By virtue of the phosphine ligand-effect in the addition of an acyl anion to α,β-enones, enantioselective 1,2-addition of acylzirconocene chloride to cyclic α,β-enones was carried out in modest optical purity (∼66% ee) by the use of 5xa0mol% Pd(OAc)2-(R)-MOP (Pd/P=1:2) catalyst. The origin of the enantioselectivity was deduced by considering an (R)-MOP coordinated π-allylic acyl Pd complex.

Copper(I)-catalyzed reaction of acylzirconocene chloride: cross-coupling and conjugate addition

Abstract For the purpose of exploring a new reaction of acylzirconocene chloride as an acyl anion donor, Cu(I)-catalyzed cross-coupling and conjugate addition reactions of acylzirconocene chloride were studied. The coupling reaction with allylic or propargylic halides efficiently proceeded to yield β,γ-unsaturated ketone or allenyl ketone derivatives, respectively. The conjugated addition reaction to α,β-enones was carried out in the presence of 2xa0equiv. of BF 3 ·OEt 2 giving 1,4-diketone compounds.

Copper(I)-catalyzed cross-coupling reaction of acylzirconocene complexes with allylic and/or propargylic halides

Abstract Efficient cross-coupling reaction of acylzirconocene chloride with allylic and/or propargylic halides was attained by utilizing a catalytic amount of a Cu(I) salt to give allylic and/or allenic ketones, respectively, in good yields. The mild Cu(I)-catalyzed reaction of acylzirconocene chloride offered an alternative protocol for the generation of an ‘unmasked’ acyl anion.

Pd-catalyzed acylation of α,β-ynone with acylzirconocene chloride and one-pot formation of cyclopentenone derivatives

Abstract Acylzirconocene chloride as an ‘unmasked’ acyl anion donor reacted with α,β-ynones to give 1,4-regioselective acylation products by the use of a catalytic amount of PdCl 2 (PPh 3 ) 2 or Pd(PPh 3 ) 4 , and a formation of a cyclopentenone derivative is observed through the reaction of α,β-unsaturated acylzirconocene chlorides and α,β-unsaturated ynones.