Synthesis of Furan-3-carboxylic and 4-Methylene-4,5-dihydrofuran-3-carboxylic Esters by Direct Palladium Iodide Catalyzed Oxidative Carbonylation of 3-Yne-1,2-diol Derivatives

Abstract

A variety of 3-yne-1,2-diol derivatives 1, bearing a primary or secondary alcoholic group at C-1, have been efficiently converted into high value added furan-3-carboxylic esters 2 in one step by PdI(2)/KI-catalyzed direct oxidative carbonylation, carried out in alcoholic media under relatively mild conditions (100 °C under 40 atm of a 4/1 mixture of CO and air). Carbonylated furans 2 were obtained in fair to excellent isolated yields (56-93%) through a sequential 5-endo-dig heterocyclization-alkoxycarbonylation-dehydration process, using only oxygen as the external oxidant. Under similar conditions, 2-methyl-3-yne-1,2-diols 3, bearing a tertiary alcoholic group, afforded 4-methylene-4,5-dihydrofuran-3-carboxylates 4 in satisfactory yields (58-70%).

Synthesis of Functionalized Heterocycles via Oxidative Carbonylation

“…Similarly, as reported later by the same group, 3-yne-1,2-diols could be transformed into furan-3-carboxylic esters through a sequential 5-endo-dig heterocyclization-alkoxycarbonylation-dehydration process using air as the external oxidant. Under similar conditions, 4-methylene-4,5-dihydrofuran-3-carboxylates were obtained from 2-methyl-3-yne-1,2-diols (Scheme 6) [39,40]. In 1991, Tamaru reported the palladium-catalyzed carbonylation of 3-butyne-1-ols.…”

PdI2-Based Catalysis for Carbonylation Reactions: A Personal Account

“…In a similar manner, 3-yne-1,2-diol derivatives were smoothly converted into furan-3carboxylates (Scheme 11a) [64,65] or 4-methylene-4,5-dihydrofuran-3-carboxylates (Scheme 11b) [65], depending on whether dehydration from the alcoholic function at C-2 occurred in an endocyclic (with substrates bearing a secondary alcoholic group at C-1) or exocyclic (tertiary alcoholic group at C-1) way, respectively. Using an ROH/HC(OR) 3 mixture as the solvent, 2-alkynylbenzamides were also subjected to PdI 2 -catalyzed oxidative carbonylation conditions and were selectively converted into isobenzofuranimine derivatives through 5-exo-dig O-heterocyclization followed by alkoxycarbonylation (Scheme 9) [61].…”

“…Synthesis of pyrrole-3-carboxylates (a) and 4-acyl-3-pyrrolecarboxylates (b) by PdI 2 -catalyzed endo heterocyclization-alkoxycarbonylation of N-Boc-1-amino-3-yn-2-ols and N-Boc-2-alkynyl-1-amino-3-yn-2-ols, respectively[63].Catalysts 2019,9, x FOR PEER REVIEW 6 of Synthesis of pyrrole-3-carboxylates (a) and 4-acyl-3-pyrrolecarboxylates (b) by PdI2catalyzed endo heterocyclization-alkoxycarbonylation of N-Boc-1-amino-3-yn-2-ols and N-Boc-2alkynyl-1-amino-3-yn-2-ols, respectively[63]. Synthesis of furan-3-carboxylates (a)[64,65] or 4-methylene-4,5-dihydrofuran-3carboxylates (b)[65] by PdI2-catalyzed oxidative endo-heterocyclization-alkoxycarbonylation of 3-yne-1,2-diol derivatives.…”

“…Synthesis of (Z)-2-[oxoisobenzofuran-1-(3H)-ylidene]acetates by PdI2-catalyzed oxidative heterocyclization-alkoxycarbonylation of 2-(ethynyl)benzoic acids[66]. Synthesis of furan-3-carboxylates (a)[64,65] or 4-methylene-4,5-dihydrofuran-3carboxylates (b)[65] by PdI 2 -catalyzed oxidative endo-heterocyclizationalkoxycarbonylation of 3-yne-1,2-diol derivatives.…”

Selective synthesis of 2,5-disubstituted furan-3-carboxylates and the isomeric 2,4-disubstituted furan-3-carboxylates

“…Methyl 4-methyl-2-phenylfuran-3-carboxylate (3a). 24 The crude product was puried by column chromatography on silica gel (0.5% ethyl acetate in petroleum ether) to give 3a as a colorless oil; yield 92%; 1 H NMR (400 MHz, CDCl 3 ): d 7. 78-7.76 (m, 2H), 7.43-7.37 (m, 3H), 7.24 (s, 1H), 3.80 (s, 3H), 2.19 (s, 3H); 13 C NMR (100 MHz, CDCl 3 ): d 165.…”