Alkylative Carbocyclization of ω‐Iodoalkynyl Tosylates with Alkynyllithium Compounds Through a Carbenoid‐Chain Process Leading to (1‐Iodoprop‐2‐ynylidene)tetrahydrofurans and ‐cyclopropanes

Abstract

Alkylative carbocyclization reactions of omega-iodoalkynyl tosylates with alkynyllithium compounds to give products with incorporated iodine atoms are described. Slow addition of 2-(3-iodoprop-2-ynyloxy)ethyl tosylates to 1-alkynyllithium compounds in tetrahydrofuran at 40 degrees C followed by additional stirring at this temperature gives (Z)-3-(1-iodoprop-2-ynylidene)tetrahydrofurans stereoselectively in good to moderate yields. Under similar conditions at 0 degrees C, 4-iodobut-1-ynyl tosylates react with 1-alkynyllithium compounds to give (1-iodoprop-2-ynylidene)cyclopropanes. The carbocyclization reactions are proposed to proceed through a new carbenoid-chain process involving the exo cyclization of a lithium acetylide intermediate and the vinylic substitution of the resulting TsO,Li-cycloalkylidenecarbenoids (Ts=tosyl) by 1-alkynyllithium compounds.

Progress in the Synthesis and Transformations of Alkylidenecyclopropanes and Alkylidenecyclobutanes

“…The slow addition of a THF solution of iodobutynyl tosylates of general structure 53 to a solution of 1-alkynyllithium 54, at 0 °C, affords the iodinated ACP derivatives 55 (Scheme 14). 15 The proposed reaction mechanism is a combination of Knorr's type process, proposed for the formal substitution of a vinyl bromide by an organolithium compound, 16 and the process proposed by the authors for a cyclization reaction of ωiodoalkynes. 17 The I/Li exchange reaction of iodoalkyne 56 with RLi affords the corresponding lithium acetylide 57, which undergoes an exo-trig cyclization followed by a vinylic substitution of the cycloalkylidenecarbenoid to produce the alkenyllithium intermediate 59.…”

“…A carbenoid chain process is proposed for the alkylative carbocyclization of ω-iodoalkynyl tosylates with alkynyllithium compounds. The slow addition of a THF solution of iodobutynyl tosylates of general structure 53 to a solution of 1-alkynyllithium 54 , at 0 °C, affords the iodinated ACP derivatives 55 (Scheme ) …”

Kinetics of Nucleophilic Substitution of Compounds Containing Multiple Leaving Groups Bound to a Neopentyl Skeleton

“… 18 In addition, I 3 Np was prepared from (TsO) 3 Np with tetrabutylammonium iodide (TBAI) in toluene under reflux, an approach inspired by the literature. 19 Br 3 Np was prepared using the same procedure but with TBABr. According to the literature, we first tried to prepare (TfO) 3 Np using triethylamine (TEA) as a base, 20 but we observed an inseparable reaction mixture, even at −20 °C, most likely due to TEA quaternization.…”

“…Using published procedures, we prepared Cl 3 Np, (MsO) 3 Np, and (TsO) 3 Np . In addition, I 3 Np was prepared from (TsO) 3 Np with tetrabutylammonium iodide (TBAI) in toluene under reflux, an approach inspired by the literature . Br 3 Np was prepared using the same procedure but with TBABr.…”

Cooperative Photoredox- and Nickel-Catalyzed Alkylative Cyclization Reactions of Alkynes with 4-Alkyl-1,4-dihydropyridines

“…In the course of our study to expand the utility of 4-alkyl-1,4-dihydropyridines toward alkylative reactions, we next planned to apply 4-alkyl-1,4-dihyropyridines to the alkylative cyclization reactions of haloalkynes. , Indeed, transition-metal-catalyzed alkylative cyclization reactions have been explored intensively to prepare the corresponding cyclic compounds valuable for both biological and pharmaceutical utilities. − As a selected example, Knochel and co-workers reported nickel-catalyzed alkylative cyclization reactions of 6-iodohex-1-ynes with alkyl zinc reagents to afford the corresponding alkylated cyclopentylidenes, where a lower temperature was required to suppress side reactions (Chart A) . Thus, we have applied 4-alkyl-1,4-dihydropyridines to the alkylative cyclization reactions of 6-iodohex-1-ynes in the presence of photoredox and nickel dual catalysts .…”