Heating of 3,5-disubstituted 4-bromo-3-methoxycarbonyldihydro-2(3H)-furanones with NaI in 3-pentanone gave 3,5-disubstituted 2(5H)-furanones in 55.8–93.3% isolated yields. A total synthesis of (±)-acarenoic acid was established in 33% overall yield via 4 steps.
Synthesis of 2-(5H)-furanones by cyclization of alkyl allene carboxylates in triflic acid
作者:Oussama Abdelhamid Mammeri、Ilia M. Baranov、Alexandr Yu Ivanov、Irina A. Boyarskaya、Aleksander V. Vasilyev
DOI:10.1016/j.tet.2023.133649
日期:2023.10
(triflic acid, TfOH) at room temperature or 70 °C for 30 min are cyclized to form 2-(5H)-furanones in yields up to 83%. The reaction cationic intermediates, O-monoprotonated [R2(R3)C=C=C(R1)–C(=O+H)OAlk] and O,C-diprotonated [R2(R3)C+–CH=C(R1)–C(=O+H)OAlk] forms of starting allenes, have been studied experimentally by NMR and theoretically by DFT calculations. It has been found that the cyclization proceeds
Allenyl alcohols such as 4-hydroxybuta-1,2-dienes and 5-hydroxypenta-1,2-dienes having a variety of substituents undergo cyclocarbonylation in the presence of a ruthenium catalyst under mild conditions selectively to give five- and six-membered lactones in a high yield with 100% atom economy. 5-Aminopenta-1,2-dines are also cyclocarbonylated to give gamma-lactams. A possible carbonylation mechanism involving a ruthenium cluster intermediate is proposed on the basis of experimental results.
Ruthenium-Catalyzed Cyclic Carbonylation of Allenyl Alcohols. Selective Synthesis of γ- and δ-Lactones
[GRAPHICS]Ruthenium complex catalyzed carbonylation of allenyl alcohols quantitatively gave cyclic carbonyl compounds, gamma- and delta-lactones, in which the hydroxy group of allenyl alcohols participated in the cyclization, A wide variety of allenyl alcohols, such as mono, di-, and trisubstituted alcohols, can be used in this reaction to produce 3- and 4-substituted gamma-lactones. Similarly, the cyclic carbonylation of 3,4-pentadien-1-ol 10a and 2-methyl-4,5-hexadien-2-ol 11a gave delta-lactones, 5,6-dihydro-3-methyl-2H-pyran-2-one 10b, and 5,6-dihydro-6,6-dimethyl-3-methyl-2H-pyran-2-one 11b, respectively, in a quantitative yield.