Palladium(II)-Catalyzed Intramolecular 1,4-Oxyacyloxylation of Conjugated Dienes. A Stereocontrolled Route to Fused Six-Membered Lactones and Pyrans

Abstract

Stereocontrolled palladium(II)-catalyzed intramolecular 1,4-oxidations of dienyl acids and alcohols proceed under mild conditions to give fused delta-lactones and pyrans, respectively, in good yields. The stereo- and regioselectivity was affected by the presence of LiCl and solvent composition (HOAc/acetone). The products obtained were used for further functionalizations using copper(I)-mediated reactions. Stoichiometric reactions of preformed dibutylcyanocuprates with pyrans containing an allylic acetate gave cis- and trans-fused ring systems with high gamma-selectivity and in high yields.

Reductive Passerini/Tsuji–Trost Strategy towards β,γ-Unsaturated Amides

“…In the case of aryl-substituted alkenes (Table 2, entries 1, 2, 5-7), the formation of the conjugated alkene may be explained by a reduction involving a more stable η 1 -allyl palladium formate complex as previously observed by Bäckvall et al 11 The regioselectivity observed for 2c might be explained using similar arguments with the double bond preferring an endocyclic position. Chelation with the amide function might be involved as well but trials with other α,β-unsaturated aldehydes should be made to confirm this behavior.…”

C−C, C−O, C−N Bond Formation on sp2Carbon by Pd(II)-Catalyzed Reactions Involving Oxidant Agents

“…In this case, too, Pd complexation of the allylic substrates dictates the access to cis-or trans-substituted bicyclic systems (Scheme 95). 131 A benzoxylated γ-lactone was also synthesized.…”

Recent Development in Palladium-Mediated Synthesis of Oxygen Heterocycles

“…The stereo-and regioselectivity of the intramolecular palladium(II)-catalyzed 1,4-oxidation reactions of 1,3-dienes bearing a side chain with a carboxylic or alcoholic nucleophiles 145a and 145b, were highly affected by the presence of additives and solvent composition 101 Trost and collaborators demonstrated a highly efficient and atom economic dual catalytic approach comprised of two distinctly separate reaction strategy (i) Ru-catalyzed intermolecular enyne crosscoupling 108 to 1,4-diene followed by (ii) intramolecular nucleophilic trapping of π-alkylpalladium species, in a one-pot reaction sequence for the synthesis of enantio-and diastereo pure O-heterocycles. 109 A different catalytic combination Pd 2 (dba) 3 .CHCl 3 , and L-1 were employed for the enantioselective Oheterocyclization.…”