Carbonylation of Alkynyl Epoxides:  Synthesis of 5-Hydroxy-2,3-dienoate Esters and 2,3-Dihydrofuran-3-ol Derivatives

Abstract

The carbonylation of alkynyl oxiranes catalyzed by (MePh(2))(4)Pd in the presence of 20 atm of carbon monoxide in methanol gives methyl 5-hydroxy-2,3-pentadienoates in good yields. When the reaction is performed on alkynyl oxiranemethanol derivatives, 4,5-dihydrofuran-3-ol derivatives are obtained stereoselectively. These products arise from the spontaneous cyclization of a dihydroxyallenyl ester intermediate.

Synthesis of δ-lactones from 2-alkynyl epoxides and 4-alkynyl-1,3-dioxolan-2-ones by palladium catalysed carbonylation and conjugate nucleophilic addition

“…The dioxolanone 3d gave the allene 6d in 70% yield whereas the corresponding epoxide 5c gave the same allene in just 53% yield under our conditions (Table 1). As expected, 6 the carbonylation appeared to proceed with high diastereoselectivity. A 2.5 : 1 mixture of diasteroisomers of dioxolanone 3c was transformed into a 2.5 : 1 mixture of diastereoisomers of allene 6c.…”

Sodium Iodide/tert‐Butyl(dimethyl)silyl Chloride‐Induced Isomerization of 2,3‐Allenols to 2(E)‐Enals

“…Compound 5a was prepared according to the literature procedure 21. To a flask was added 5aa (401.1 mg, 2 mmol), MeOH (10 mL), and Pd(PPh 3 ) 4 (46.6 mg, 0.04 mmol) sequentially.…”

Synthesis of α-Allenic Esters (Acids)

“…Consequently, the palladium(0)-catalyzed reaction was applied to several different substrates including allenyl and propargyl halides, 12 tertiary propargyl alcohols using a Pd(II) complex, 13 cyclic alkynyl carbonates, 14 propargyl mesylates, 15 alkynyl oxiranes, 16 and alkynyl dioxolanones (Scheme 7). 17 In general, Pd(0) catalysts like Pd(dba) 2 , Pd(OAc) 2 , Pd[P(C 6 H 4 ) 3 ] 4 were utilized in the presence of a chelating phosphine such as 1,2-bis(diphenylphosphino)ethane (dppe), 1,3-bis(diphenylphosphino)propane (dppp) or triphenylphosphine.…”