LDA-Catalyzed Cycloisomerization of 2-(2-Propynyloxy)ethyl Iodides Leading to 3-(Iodomethylene)tetrahydrofurans

Harada, Toshiro; Muramatsu, Keiko; Fujiwara, Takayuki; Kataoka, Hiroshi; Oku, Akira

doi:10.1021/ol047570e

Cited by 12 publications

(5 citation statements)

References 17 publications

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“…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. I/Li exchange furnishes the final product 60 (Scheme 15).…”

Section: Alkylidenecyclopropanes 21 Syntheses Of Methylene-and Alkyli...mentioning

confidence: 99%

Progress in the Synthesis and Transformations of Alkylidenecyclopropanes and Alkylidenecyclobutanes

et al. 2014

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Section: Alkylidenecyclopropanes 21 Syntheses Of Methylene-and Alkyli...mentioning

confidence: 99%

Progress in the Synthesis and Transformations of Alkylidenecyclopropanes and Alkylidenecyclobutanes

et al. 2014

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“…The use of inexpensive, nontoxic alkali, alkali earth, and main group elements − in the place of transition metals in catalysis is a rapidly developing field. Recently, it was found that tetramethylethylenediamine (TMEDA)-supported lithium amides are catalysts for the guanylation of electron-deficient amines, operating efficiently under mild reaction conditions .…”

Section: Introductionmentioning

confidence: 99%

Amidolithium and Amidoaluminum Catalyzed Synthesis of Substituted Guanidines: An Interplay of DFT Modeling and Experiment

et al. 2008

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The synthesis of substituted guanidines is of significant interest for their use as versatile ligands and for the synthesis of bioactive molecules. Lithium amides supported by tetramethylethylenediamine have recently been shown to catalyze the guanylation of amines with carbodiimide. In this report, density functional theory (DFT) calculations are used to provide insight into the mechanism of this transformation. The mechanism identified through our calculations is a carbodiimide insertion into the lithium-amide bond to form a lithium guanidinate, followed by a proton transfer from the amine. The proton transfer transition state requires the dissociation of one of the chelating nitrogen centers of the lithium guanidinate, proton abstraction from the amine, and bond formation between the lithium center and the amine nitrogen. On the basis of this mechanism, further calculations predicted that aluminum amides would also function as active catalysts for the guanylation of amines. We confirm this experimentally and report the development of aluminum amides as a new main group catalyst for the guanylation of a range of electron-poor amines with carbodiimide.

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“…Herein, we wish to report cycloisomerization of iodoalkynes and diiodoalkynes to afford (iodomethylene)- and (diiodometh-ylene)cycloalkanes through a novel carbenoid-chain process involving exo -cyclization of the acetylide intermediate. The extension of the reactions to an atom-transfer-type cyclization of 13 (eq 4) as well as some mechanistic aspects in exo -cyclization of acetylides are also described …”

Section: Introductionmentioning

confidence: 99%

Carbocyclization Reaction of ω-Iodo- and 1,ω-Diiodo-1-alkynes without the Loss of Iodine Atoms through a Carbenoid-Chain Process

et al. 2007

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Atom-economical carbocyclization reactions of omega-iodo-1-alkynes and 1,omega-diiodo-1-alkynes to give products with incorporation of iodine atoms is described. Cycloisomerization of 2-(2-propynyloxy)ethyl iodides is initiated by a catalytic amount of LDA to give 3-(iodomethylene)tetrahydrofurans in high yields. Upon treatment of with a catalytic amount of 1-hexynyllithium, 1,omega-diiodo-1-alkynes efficiently undergo cycloisomerization to give (diiodomethylene)cycloalkanes. The diiodomethylene products are also obtained by iodine atom-transfer-type cyclization of omega-iodo-1-alkynes, using 1-iodo-1-hexyne as an external iodine atom source. Bromine atom-transfer and proton-transfer cyclization proceed as well by employing 1-bromo-1-octyne and 1-octyne, respectively. These reactions are proposed to proceed through a carbenoid-chain process involving exo-cyclization of the lithium acetylide intermediates to give Li,I-alkylidene carbenoids. It is shown that the exo-cyclization proceeded stereospecifically through inversion of the stereochemistry at the electrophilic carbon.

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LDA-Catalyzed Cycloisomerization of 2-(2-Propynyloxy)ethyl Iodides Leading to 3-(Iodomethylene)tetrahydrofurans

Cited by 12 publications

References 17 publications

Progress in the Synthesis and Transformations of Alkylidenecyclopropanes and Alkylidenecyclobutanes

Progress in the Synthesis and Transformations of Alkylidenecyclopropanes and Alkylidenecyclobutanes

Amidolithium and Amidoaluminum Catalyzed Synthesis of Substituted Guanidines: An Interplay of DFT Modeling and Experiment

Carbocyclization Reaction of ω-Iodo- and 1,ω-Diiodo-1-alkynes without the Loss of Iodine Atoms through a Carbenoid-Chain Process

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