New Convenient One-Pot Methods of Conversion of Alkynes to Cyclobutenediones or α,β-Unsaturated Carboxylic Acids Using Novel Reactive Iron Carbonyl Reagents

Abstract

Reactions of NaHFe(CO)4/RX or [HFe3(CO)11]- reagents with alkynes lead to the formation of the corresponding α,β-unsaturated carboxylic acids and/or the cyclobutenediones. The reagent generated in situ using the NaHFe(CO)4/CH3I combination in THF, on reaction with alkynes followed by CuCl2·2H2O oxidation, gives the corresponding cyclobutenediones (27−42%) and α,β-unsaturated carboxylic acids (10−22%), whereas the reagent generated using CH2Cl2 in place of CH3I leads to α,β-unsaturated carboxylic acids (37−60%) and their derivatives (35−55%) at 25 °C. The same reagent system in the presence of acetic acid (4 equiv) yields the corresponding cyclobutenedione (33%). The reaction using Me3SiCl gives the corresponding α,β-unsaturated carboxylic acids (45−54%) at 25 °C and the corresponding cyclobutenediones (51−63%) at 60 °C. Interestingly, the reaction of the [HFe3(CO)11]- species generated using Fe(CO)5/NaBH4/CH3COOH, with alkynes at 25 °C, followed by CuCl2·2H2O oxidation gives the corresponding cyclobutenediones (60−73%). The possible intermediates and pathways for the formation of α,β-unsaturated carboxylic acids and cyclobutenediones are discussed.

Double carbonylation and beyond: systems at work and their organometallic models

“…Though catalytic or stoichiometric triple carbonylation processes have never been observed, some complexes that might be considered as models for such reactions have been described in the literature. A series of platinum complexes of general form- (57). 94 A similar series of iron compounds is reported in Table 1.…”

Microwave‐Assisted Aminocarbonylation of Ynamides by Using Catalytic [Fe3(CO)12] at Low Pressures of Carbon Monoxide

“…[41] With the aim to reduce the amount of nucleophile required, different amines [31c] were tested to generate the catalytically active species "amine-[Fe(CO) 4 ]". [33][34][35]42] By using 1,8-diazabicycloundec-7-ene (DBU) or N,N-diisopropylethylamine (DIPEA) and 2 (1.2 equiv), almost the same yield of 3 was observed (entries 4 and 5, Table 1). The addition of DMF or NH 3 produced a dramatic reduction in reaction yields (entries 7 and 8, Table 1), whereas triethylamine (TEA, 4 equiv) gave 3 in 70 % isolated yield after microwave irradiation for 15 min at 90 8C, in the presence of CO (1.3 bar) and nPrNH 2 (1.2 equiv; entry 6 , Table 1).…”

Stereoselective synthesis of α,β-unsaturated carboxylic acids from alkynes using the Fe(CO)5/t-BuOK/AcOH/CH2Cl2 reagent system

“…Initially, the Fe(CO) 5 would react with alkoxide, CH 3 COOH and CH 2 Cl 2 to provide the Fe(CO) 4 intermediates, which could further react with MHFe(CO) 4 to give the [HFe 3 (CO) 11 ] À species as outlined in Scheme 4. Reaction of these species with alkynes could lead to the acyl complex 5 or iron complex 4 (Scheme 4) which are expected to give the a,b-unsaturated carboxylic acids after CuCl 2 $2H 2 O oxidation [33]. Previously, we have explained the hydrocarboxylation of alkynes by considering the hydrometallation pathway involving the [HFe 3 (CO) 11 ] À species [33].…”

“…Reaction of these species with alkynes could lead to the acyl complex 5 or iron complex 4 (Scheme 4) which are expected to give the a,b-unsaturated carboxylic acids after CuCl 2 $2H 2 O oxidation [33]. Previously, we have explained the hydrocarboxylation of alkynes by considering the hydrometallation pathway involving the [HFe 3 (CO) 11 ] À species [33]. However, the formation of traces of cyclobutenediones along with a,bunsaturated carboxylic acids in this transformation indicates that the mechanism involving the intermediacy of an a,b-unsaturated carbonyl complex 4 [35] and subsequent protonolysis to give the corresponding acyl complex 5 cannot be also ruled out (Scheme 4) [41].…”