The Metalation of Phenoxazine and Some of its Derivatives<sup>1</sup>

Gilman, Henry; Moore, Leonard O.

doi:10.1021/ja01542a040

Cited by 9 publications

(8 citation statements)

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“…See http : //www.rsc.org/suppdata/nj/ b0/b008503k/ bis(ether nitrile) 5a or 5b (Scheme 1, path B). In fact the rate of the intramolecular meta-Ñuoro displacement reaction, involving cyclisation, was greatly accelerated relative to the previously described intermolecular meta-Ñuoro displacement2 and cyanodibenzo [1,4]dioxines 4 were formed in quantitative yields.…”

Section: Introductionmentioning

confidence: 68%

“…We had previously established that the "" high-temperature ÏÏ reaction at 130 ¡C between 1a and 2a in DMF gave 1-cyanodibenzo [1,4]dioxine 8a in 99% yield. 1 Reactions have now been carried out in DMSO at room temperature for periods of 24 h and 5 days.…”

Section: Resultsmentioning

confidence: 99%

“…70%) and attempts at further puriÐcation by sublimation reduced the overall yields as the products decomposed or oligomerised. Thus, hydrolysis of cyanophenoxazines was not found to be a good route to carboxyphenoxazines, in contrast to hydrolysis of cyanodibenzo [1,4]dioxines which gives good yields of carboxydibenzo [1,4]…”

Section: Reactions With Aminophenolsmentioning

confidence: 97%

“…We recently reported a procedure for the simple and quantitative synthesis of a new family of cyano-substituted dibenzo [1,4]dioxines1 involving a cyano-activated Ñuoro displacement reaction between catechol 1a, or a catechol derivative, and either 2,3-or 3,4-diÑuorobenzonitrile 2a or 2b in an aprotic solvent, DMF, in the presence of potassium carbonate at 130 ¡C (Scheme 1). The reaction involved a combination of either a facile ortho-or para-Ñuoro displacement reaction and a, presumably, subsequent and less facile meta-Ñuoro displacement reaction ; previous work demonstrated that cyanoactivated Ñuoro displacement with 3-Ñuorobenzonitrile will proceed in N-methylpyrrolidinone (NMP) but only at the higher temperature of about 170 ¡C.2 Following the initial displacement reaction, it is conceivable that reaction of the Ðrst-formed product 3a or 3b could follow either of two routes, an intramolecular cyclisation reaction (Scheme 1, path A) to form a cyanodibenzo [1,4]dioxine 4a or 4b or an intermolecular reaction with a second molecule of 2a or 2b to form a ¤ Electronic supplementary information (ESI) available : 13C NMR data for cyanophenoxazines and related compounds, crystal structures of compounds 17 and 18.…”

Section: Introductionmentioning

confidence: 99%

“…The reaction involved a combination of either a facile ortho-or para-Ñuoro displacement reaction and a, presumably, subsequent and less facile meta-Ñuoro displacement reaction ; previous work demonstrated that cyanoactivated Ñuoro displacement with 3-Ñuorobenzonitrile will proceed in N-methylpyrrolidinone (NMP) but only at the higher temperature of about 170 ¡C.2 Following the initial displacement reaction, it is conceivable that reaction of the Ðrst-formed product 3a or 3b could follow either of two routes, an intramolecular cyclisation reaction (Scheme 1, path A) to form a cyanodibenzo [1,4]dioxine 4a or 4b or an intermolecular reaction with a second molecule of 2a or 2b to form a ¤ Electronic supplementary information (ESI) available : 13C NMR data for cyanophenoxazines and related compounds, crystal structures of compounds 17 and 18. See http : //www.rsc.org/suppdata/nj/ b0/b008503k/ bis(ether nitrile) 5a or 5b (Scheme 1, path B).…”

Section: Introductionmentioning

confidence: 99%

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Cyano-activated fluoro displacement reactions in the synthesis of cyanophenoxazines and related compounds

Eastmond¹,

Gilchrist²,

Paprotny³

et al. 2001

New J. Chem.

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Cyano-activated Ñuoro displacement reactions between 2,3-and 3,4-diÑuorobenzonitriles and the nucleophiles catechol, 2-aminophenol, 2-aminobenzenethiol and benzene-1,2-dithiol either in DMF at 130 ¡C or in DMSO at rt, in the presence of potassium carbonate, lead to new substituted heterocycles or other species in high yield. Catechol at rt gives quantitative yields of cyanodibenzo[1,4]dioxines. 2-Aminophenol and 2-aminobenzenethiol at 130 ¡C give cyanophenoxazines and cyanophenothiazines, respectively, while at rt 2-aminophenol yields (aminophenoxy)cyanoÑuorobenzenes which can be converted into di †erent cyanophenoxazines on heating in the presence or absence of base. The base-catalysed reactions involve a Smiles rearrangement. Benzene-1,2-dithiol yields cyanothianthrenes (130 ¡C) or a mixture of cyanothianthrene and bis(cyanoÑuorophenylsulfanyl)benzenes at rt.

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Section: Introductionmentioning

confidence: 68%

Section: Resultsmentioning

confidence: 99%

Section: Reactions With Aminophenolsmentioning

confidence: 97%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Cyano-activated fluoro displacement reactions in the synthesis of cyanophenoxazines and related compounds

Eastmond¹,

Gilchrist²,

Paprotny³

et al. 2001

New J. Chem.

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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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