Novel cyclization reaction of 1,ω-diiodo-1-alkynes without the loss of iodine atoms

Harada, Toshiro; Mizunashi, Kenta; Muramatsu, Keiko

doi:10.1039/b516515f

Cited by 11 publications

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“…2 We have recently reported that 1,w-diiodoalkynes 1 undergo a novel cycloisomerization to give (diiodomethylene)cycloalkanes 2 in the presence of a catalytic amount of 1-hexynyllithium (Scheme 1). 3 The cycloisomerization reaction is believed to proceed through a chain mechanism involving exo cyclization of lithium acetylides 3 to form lithium alkylidene carbenoids 4 as a key step. 4 Thus, acetylide 3 is first generated by iodine-lithium exchange reaction of substrate 1 with 1-hexynyllithium, and then undergoes the exo cyclization to give carbenoid 4, which is efficiently trapped by 1 to give product 2 with simultaneous regeneration of the acetylide intermediate 3.…”

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“…Iodobenzene and 2-iodothiophene are much less efficient in iodination of carbenoid 4, which rather undergoes proton abstraction from 5 leading to the formation of monoiodo product 6 5 (Table 1, entries 1 and 2). When 5a was treated at -20 °C with 1-iodohexyne (1.1 equiv) and 1-hexynyllithium (0.4 equiv) for 2 hours, a 39:61 mixture of diiodoalkyne 1a [R 1 , R 2 = -(CH 2 ) 5 , R 3 = H] and 5a was obtained without the formation of 2a. The observation suggests an alternative pathway (Scheme 2, pathway b) involving iodination of carbenoid 4 by diiodoalkyne 1 which is formed reversibly by iodination of 3 with 1-iodohexyne.…”

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Iodine-Atom-Transfer-Type Carbocyclization of 2-(2-Propynyloxy)ethyl Iodides Involving a Lithium Alkylidene Carbenoid Intermediate

Harada¹,

Kitano²,

Mizunashi³

2007

Synlett

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Iodine-Atom-Transfer-Type Carbocyclization of 2-(2-Propynyloxy)ethyl Iodides Involving a Lithium Alkylidene Carbenoid Intermediate

Harada¹,

Kitano²,

Mizunashi³

2007

Synlett

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Three characteristic reactions of alkynes with metal compounds in organic synthesis

Omae

2008

Applied Organom Chemis

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IntroductionBoth alkynes and alkenes are compounds having at least one π -electron bond. Therefore, in these compounds, reactions such as the addition of hydrogen, the addition of halogens, the addition of hydrogen halides, metathesis, oxidation and polymerization, proceed in the presence of metal compounds.However, alkynes have another set of π -electron bonds. These two sets of π -electron bonds in alkynes are mutually orthogonal. Hence, the reactions of alkynes in the presence of the metal compounds are different from the reactions of alkenes.As described in the next section, the two sets of mutually orthogonal π -electron bonds tend to easily bond with d-electrons in transition metals. Consequently, the characteristic reactions of alkynes occur in the presence of the transition metals. In these transition metal compounds, especially, a Co-Co bond in (CO) 4 Co-Co(CO) 4 , very easily form a mutually bridged bond with the two sets of π -electron bonds in alkynes. These reactions of alkynes with alkenes in the presence of Co 2 (CO) 8 are the most characteristic reactions of alkynes with the transition metals in organic synthesis.This first type of characteristic reaction of alkynes with organocobalt compounds is the Pauson-Khand reactions. Reactions that are similar to the Pauson-Khand reactions, Pauson-Khand-type reactions, occur in the presence of the other transition metal compounds besides the cobalt carbonyl compounds, and also proceed as the first type of characteristic reactions. The Pauson-Khand reactions and Pauson-Khand-type reactions are the reactions of alkynes, alkenes and carbon monoxide. In these three components, alkynes and carbon monoxide have two sets of π -electron bonds and alkenes have one set of π -electron bond. These reactions are also called as the [2 + 2 + 1] cyclizations.The second type of characteristic reactions of alkynes with the transition metal compounds is other cyclizations in which alkynes react with compounds having π -electron bonds such as other alkynes, alkenes, allenes, aldehydes, ketones, imines, carbon monoxide, carbon dioxide and nitriles. These reactions are cyclooligomerizations and cycloadditions.The third type of characteristic reaction of alkynes in the presence of the metal compounds is coupling reactions in which the negative charge of the carbon atom in alkynes is involved in addition to the high reactivity to the π -electron bond. The reactions are carbonylations, dioxycarbonylations, coupling reactions with aldehydes, ketones, imines, alkenes, allyl compounds, alkynes, other oxygen-containing compounds or nitrogen-containing compounds, Sonogashira reactions and other coupling reactions.The characteristic reactions of alkynes with organocobalt compounds in organic synthesis have been reported in a previous review article. [1] This present review reports mainly on three characteristic reactions of alkynes with the metal compounds in organic synthesis, excluding the organocobalt compounds. * Correspondence to : Iwao Omae, Nihon Pharmaceutical University, 10281 ...

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

Harada

Imaoka

Kitano

et al. 2010

Chemistry A European J

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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.

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Novel cyclization reaction of 1,ω-diiodo-1-alkynes without the loss of iodine atoms

Abstract: In the presence of 1-hexynyllithium (0.2-0.6 equiv.), 1,omega-diiodo-1-alkynes undergo a new type of cyclization reaction without the loss of two iodine atoms to afford (diiodomethylene)cycloalkanes.

Cited by 11 publications

References 12 publications

Iodine-Atom-Transfer-Type Carbocyclization of 2-(2-Propynyloxy)ethyl Iodides Involving a Lithium Alkylidene Carbenoid Intermediate

Iodine-Atom-Transfer-Type Carbocyclization of 2-(2-Propynyloxy)ethyl Iodides Involving a Lithium Alkylidene Carbenoid Intermediate

Three characteristic reactions of alkynes with metal compounds in organic synthesis

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

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