Isomerisation, alkylation and hydroxyalkylation of cumulenyl ethers

Selling, H. A.; Rompes, J. A.; Montijn, P. P.; Hoff, S.; Boom, Jacques H. van; Brandsma, L.; Arens, J. F.

doi:10.1002/recl.19690880115

Cited by 15 publications

(1 citation statement)

References 2 publications

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“…Using a catalytic amount of NaH led to a lower conversion, while secondary reactions still occurred (entry 4). When performing the reaction in DMSO with KO t Bu as the base, 7% conversion to an addition product 9 was observed (entry 5). Although allene 8b was not detected, this addition product caught our interest given the position of the double bond .…”

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3-Imidoallenylphosphonates: In Situ Formation and β-Alkoxylation

et al. 2016

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3-Imidoallenylphosphonates, allenes bearing both an electron-withdrawing and -donating group, were isolated for the first time. An alkoxy substituent was introduced into these unprecedented intermediates in a one-pot approach, yielding β-functionalized aminophosphonates in excellent yields and short reaction times. The mechanistic insights gained are important additions to the domain of allene chemistry. Addition of biologically important molecules, including monoglycerides, amino acids, and nucleosides, proves the general applicability of the developed method.

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3-Imidoallenylphosphonates: In Situ Formation and β-Alkoxylation

et al. 2016

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Heteroatom‐Facilitated Lithiations

Gschwend¹,

Rodriguez²

1979

Organic Reactions

185

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Some 25 years have elapsed since the topic of metalation reactions was reviewed by Gilman and Morton. The intervening years have been notable for intensive explorations in this area, in part because many organolithium reagents are now commercially available. Specifically, research efforts have been characterized by the discovery of new functional groups that promote metalation, elaboration of novel heterocyclic and olefinic substrates as metalatable species, recognition of new types of lithiating agents, and the continuation of efforts to define accurately the mechanism of metalation. Accordingly, heteroatom‐facilitated lithiation has become recognized as an increasingly important tool, not only in the elaboration of carbocyclic aromatic and heteroaromatic systems, but also in synthetic aliphatic chemistry. A few recent reviews have covered the topic in a more limited or less specific sense. It is the purpose of this chapter to survey and classify the vast accumulation of heteroatom‐facilitated lithiations recorded since the first coverage in Organic Reactions . As outlined by Gilman and Morton, the terms “metalation” in general and “lithiation” in particular denote any replacement of a hydrogen atom by metal or lithium. In this review, however, lithiation is defined as the exchange of a hydrogen atom attached to an sp 2 ‐hybridized carbon atom by lithium to form a covalent lithium‐carbon bond. More specifically, discussion is limited to those metalations that, through the influence of a heteroatom, are characterized by rate enhancement and regioselectivity. In fact, lithiation reactions of this type are noted for an extraordinarily high degree of regioselectivity, metalation generally occurring on the sp 2 ‐carbon atom closest to the heteroatom. Based on the relative position of the heteroatom, such lithiations are conveniently classified into two principal categories: alpha and beta ( ortho ) lithiations. In alpha lithiations the metalating agent deprotonates the sp 2 ‐carbon atom alpha to the heteroatom to form a carbonlithium bond. This sp 2 ‐carbon atom may be part of an olefinic or heteroaromatic π system. In beta lithiations the metalating agent is directed to deprotonate the sp 2 ‐carbon atom beta to the heteroatom‐containing substituent. The sp 2 ‐carbon atom can be part of an aromatic or an olefinic π system. It should be noted that the designation “ ortho metalation” is used specifically for the beta metalation of carbocyclic aromatic systems. This chapter surveys all systems in which alpha and beta lithiations have been observed, with the exception of ferrocenes.

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Allylic and Benzylic Carbanions Substituted by Heteroatoms

Biellmann

Ducep

1982

Organic Reactions

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This review covers allylic and benzylic carbanions in which a heteroatom and the double bond may be part of a conjugated system. Propargylic and allenic systems are also included. The cation is an alkaline or alkaline‐earth element; transition metals are excluded. The chapter by Gilman and Morton in 1954 was restricted to lithium derivatives. Reviews covering part of the subject include those on organometallic compounds, on reagents for nucleophilic acylation, on olefin synthesis with P(O)‐activated reagents, on the formation and reactions of carbanions derived from allylic sulfoxides, dithianes, nitrosoamines, thioethers and ethers, selenium compounds, on base‐catalyzed isomerization, and on rearrangements of carbanions. Allylic and benzylic carbanions adjacent to the following heteroatoms have been described: boron, nitrogen, oxygen, silicon, phosphorus, sulfur, chlorine, selenium, bromine, tellurium. The basicity and structures of these anions are considered first. This discussion is followed by sections on methods of generation of carbanions, reactions occurring during preparation, decomposition, and rearrangements of carbanions, reactions with electrophiles, regioselectivity and stereochemical aspects of the reactions, transformations of the reaction products, and some applications of these carbanions in synthesis.

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Isomerisation, alkylation and hydroxyalkylation of cumulenyl ethers

Cited by 15 publications

References 2 publications

3-Imidoallenylphosphonates: In Situ Formation and β-Alkoxylation

3-Imidoallenylphosphonates: In Situ Formation and β-Alkoxylation

Heteroatom‐Facilitated Lithiations

Allylic and Benzylic Carbanions Substituted by Heteroatoms

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