Carbamoyllithiums. A Novel Method for Generation by Lithium-Tellurium Exchange Reaction

Hiiro, Tomoki; Mogami, T.; Kambe, Nobuaki; Fujiwara, Sayaka; Sonoda, Noboru

doi:10.1080/00397919008052313

Cited by 37 publications

(3 citation statements)

References 20 publications

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“…[2][3][4][5][6][7] Among them, we already disclosed that carbamoyllithiums were generated efficiently by tellurium-lithium exchange reaction 8 of carbamotelluroates with organolithium reagents, and many amide derivatives were obtained by the trapping with various electrophiles. 5 This reaction is of great synthetic value since onepot operation starting from carbamoyl chlorides in a large scale has been established and easy isolation of the products is possible. 5b During the course of our study on the generation and synthetic use of carbamoyllithiums, we faced two problems: (i) carbamoyllithiums 1, having a hydrogen(s) on the nitrogen, rapidly rearrange to azaenolates of the corresponding formamides; 9 and (ii) carbamoyllithiums 2, having an aromatic substituent on the nitrogen, release CO rapidly even at low temperatures.…”

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“…Adding carbonyl functions into organic molecules is a significantly important transformation in organic synthesis, and much effort has been focused on the development of new and useful carbonyl transfer reagents . Carbamoyllithium (R 2 NC(O)Li) is one of the most straightforward reagents for the nucleophilic introduction of carbamoyl moieties into organic compounds, and several methods have been developed for the generation of carbamoyllithiums. − Among them, we already disclosed that carbamoyllithiums were generated efficiently by tellurium−lithium exchange reaction of carbamotelluroates with organolithium reagents, and many amide derivatives were obtained by the trapping with various electrophiles . This reaction is of great synthetic value since one-pot operation starting from carbamoyl chlorides in a large scale has been established and easy isolation of the products is possible 5b…”

mentioning

confidence: 99%

“…During the course of our study on the generation and synthetic use of carbamoyllithiums, we faced two problems: (i) carbamoyllithiums 1 , having a hydrogen(s) on the nitrogen, rapidly rearrange to azaenolates of the corresponding formamides; and (ii) carbamoyllithiums 2 , having an aromatic substituent on the nitrogen, release CO rapidly even at low temperatures 5b 1 Two Problems of Carbamoyllithiums …”

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Generation of Carbamoyl- and Thiocarbamoyllithium Synthons Having a Hydrogen(s) or an Aryl Group on the Nitrogen and Their Trapping with Carbonyl Electrophiles

et al. 2006

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Dimetalated amides 1 (Y = O) were generated as the synthons of carbamoyllithiums 2 (Y = O) by the reaction of isocyanates with iBu2AlTenBu and a subsequent tellurium-lithium exchange reaction. A series of amide derivatives 3 (Y = O) were obtained by the trapping of dianion 1 with electrophiles. This transformation can be successfully applied to the generation and trapping of thiocarbamoyllithium synthons 1 (Y = S) as well as to the nucleophilic introduction of the parent carbamoyl moiety H2NC(O).

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Generation of Carbamoyl- and Thiocarbamoyllithium Synthons Having a Hydrogen(s) or an Aryl Group on the Nitrogen and Their Trapping with Carbonyl Electrophiles

et al. 2006

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The Role of Ate Complexes in Halogen(Metalloid)–Metal Exchange Reactions: A Theoretical Study

Boche¹,

Schimeczek

Ciosłowski³

et al. 1998

Eur. J. Org. Chem.

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Correlated electronic structure calculations predict that [(CH3)n+1X]− methyl ate anions, where X is an element of the main groups 14, 15, 16, or 17 up to Bi, possess widely varying stabilities that are governed by the electronegativities of their central atoms X. These stabilities correlate well with the propensities of the elements in question to undergo exchange with lithium and magnesium halide, except in the cases where steric hindrance in the transition states of the exchange reactions is important. These findings are nicely confirmed by calculations of the transition states [(CH3)2XLi]# (X = Cl, Br, I) and [(CH3)3SeLi]# of the corresponding degenerate exchange reactions CH3X (X = Cl, Br, I) + CH3Li and (CH3)2Se + CH3Li, respectively. The computed relative stabilities of the mixed [R–I–CH3]− ate anions of iodine (where R = phenyl, ethynyl, vinyl, ethyl, or cyclopropyl) are in excellent agreement with the experimentally observed equilibria of the corresponding lithium–iodine exchange reactions. The recent experimental observation of a highly stable α‐iodine‐substituted iodine ate complex as an intermediate in an iodine–magnesium bromide exchange reaction is also corroborated by our studies. Thus, the present calculations provide strong evidence for ate complexes being key intermediates in halogen(metalloid)–lithium(magnesium halide) exchange reactions.

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Relative rates, relative activation parameters and substituent effects of lithium-metalloid exchange reactions

Kanda

Katō

Kambe

et al. 1996

J. Phys. Org. Chem.

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The relative reactivity of heteroatomic compounds (PhM; M = SeR, SnR3, TeR, I) towards BuLi was estimated by competitive experiments. The rates of exchange reactions in THF increase in the order I > Te >> Sn >> Se with a ratio of 1000:300:15: 1 at -70 "C when R =Bu. Me,SnPh underwent exchange much faster than Bu,SnPh, suggesting that the exchange reaction was largely affected by steric hindrance. The evidence that Bu,SnPh and BuTePh react with BuLi at almost the same rate in the presence of HMPA and that the relative exchange rates of Li-Te/Li-Sn increase in less polar solvents such as Et10 and hexane indicates that coordination of solvents towards lithium plays an important role in exchange reactions. Relative activation parameters obtained from competitive reactions of PhTeBu and PhSnBu, with BuLi showed that Li-Te exchange was favored over Li-Sn exchange by an enthalpy factor. Hammett treatment of Li-Te exchange of ArTeBu with BuLi in THF showed a substantially large positive reaction constant ( p ) of 3.4, indicating that the anion charge was largely distributed on the leaving group in the transition state.

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Carbamoyllithiums. A Novel Method for Generation by Lithium-Tellurium Exchange Reaction

Cited by 37 publications

References 20 publications

Generation of Carbamoyl- and Thiocarbamoyllithium Synthons Having a Hydrogen(s) or an Aryl Group on the Nitrogen and Their Trapping with Carbonyl Electrophiles

Generation of Carbamoyl- and Thiocarbamoyllithium Synthons Having a Hydrogen(s) or an Aryl Group on the Nitrogen and Their Trapping with Carbonyl Electrophiles

The Role of Ate Complexes in Halogen(Metalloid)–Metal Exchange Reactions: A Theoretical Study

Relative rates, relative activation parameters and substituent effects of lithium-metalloid exchange reactions

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