Lithium ammonia reductions of 2-thiophenecarboxylic acids

Abstract

Lithium/ ammonia reductions of 2-thiophenecarboxylic acids (1) in the absence of a proton source afforded mixtures of products. In the presence of methanol acyclic mercapto carboxylic acids (4) were the major products. Ring closure of 4 to the corresponding thiolactones (12) showed the double bonds in 4 to be of cis geometry. Attempts were made to prepare Z olefinic compounds derived from these mercapto carboxylic acids. Lithium 2thiophenecarboxylate salts (2) afforded good yields of the corresponding 2,5-dihydro-2-thiophenecarboxylic acids (3). The presence of substituents on the ring and the ratio of metal to acid were significant factors in determining the nature of the products. A mechanism is proposed to explain the products observed.

Enantioselective Lewis Acid Catalysis in Intramolecular [2 + 2] Photocycloaddition Reactions: A Mechanistic Comparison between Representative Coumarin and Enone Substrates

“…In our hands, best results are obtained in UV or NMR titration, when the samples are prepared individually from two stock solutions (vide infra) rather than diluting one sample further and further. 2 The titration was performed twice to explore the reproducibility in these extremely moisture-sensitive experiments. Although every operation in the described titrations has been done with maximum effort to exclude any exposure of the solutions to water, both titration sets showed a reproducible offset of the expected titration curves at approximately 0.7 mM (see Figure S12).…”

“…This interpretation was substantiated by Karl-Fischer titration, indicating a water content of the solvent of approximately 5 ppm; additional tiny amounts of water, introduced during the handling with the microliter-syringes, lead to the observed 9.5 ppm (m/m in dichloromethane). 2 A detailed description can be found in the Supporting-Information of Org. Biomol.…”

“…3 Dichloromethane (p.a.) was purified using a MBraun SPS-System and further dried over 4 Å molecular sieves for 5 days 2,3 . Analyzing the titration data based on this assumption using a global least square fit over both datasets gave a best fit for…”

Copper(I)-Catalyzed IntramolecularAddition ofN-Chloroamides to Double Bonds;an Efficient Synthesis of Lactams from Unsaturated Amides

“…To check the scope of this reaction, we prepared the amides 5g-i (Scheme 4). 8 For the synthesis of 5g-i, we reacted the acid chloride 4 with different amines whilst 5j was obtained from the known acid 7 9 via the acid chloride. The carbamate 5f was obtained by a straightforward reaction of propylisocyanate with allylic alcohol.…”

One-step and non-catalytic intramolecular redox reactions of conjugated all E-dienals to non-conjugated Z-enoic acids in subcritical water

“…Olefin metathesis using the Grubbs' II catalyst is employed to afford cyclic derivatives containing a double bond with the Z-configuration followed by ring cleavage [14]. Lithium-ammonia reduction of 2-thiophenecarboxylic acid [15] and the addition of alcohol to ketene intermediate from corresponding acid chloride in situ [16] also appeared in the literature.…”