Synthesis of Heterocyclic Cyclopolyaromatics Containing Different Kinds of Nuclei

Kauffmann, Thomas; Muke, Bernd; Otter, Rolf; Tigler, Dieter

doi:10.1002/anie.197507141

Cited by 16 publications

(2 citation statements)

References 5 publications

(1 reference statement)

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“…It is noteworthy that biphenylene can be catalytically converted into tetraphenylene,a lthough the synthetic utility of this reaction is limited by the narrow structural diversity of biphenylene derivatives. [16] In this context, we focused our attention on ad ehydrogenative coupling strategy due to the simplicity of starting materials, [17] and we herein describe the Pd-catalyzed construction of thiophene-fused COTf rameworks through the dehydrogenative cyclodimerization of 3,3'bithiophenes.T he method is applicable to various heteroaromatics,e nabling the facile synthesis of "composite" heteroarene-fused COTs (see below). [14] Despite the significant research interest in this field, there have been limited achievements [15] to date in the efficient construction of heteroarene-fused COTs besides those represented in Scheme 1a.…”

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Palladium‐Catalyzed Synthesis of Heteroarene‐Fused Cyclooctatetraenes through Dehydrogenative Cyclodimerization

2017

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Arene-fused cyclooctatetraenes (COTs) possess unique structural and electronic properties that originate from their saddle-shaped π-conjugated architectures. Considerable attention has been paid to the transition-metal-mediated synthesis of these cyclic compounds; however, there have been limited achievements to date in the efficient construction of heteroarene-fused COTs. In this contribution, we report a novel Pd-catalyzed dehydrogenative cyclodimerization of biheteroarenes through four-fold C-H activation toward the synthesis of a series of heteroarene-fused COTs. A set of mechanistic investigations indicated the involvement of high-valent Pd species prior to the dimerization event in the catalytic cycle. The redox behavior of the obtained COTs is also described briefly.

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Palladium‐Catalyzed Synthesis of Heteroarene‐Fused Cyclooctatetraenes through Dehydrogenative Cyclodimerization

2017

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“…[14] Despite the significant research interest in this field, there have been limited achievements [15] to date in the efficient construction of heteroarene-fused COTs besides those represented in Scheme 1a. [16] In this context, we focused our attention on ad ehydrogenative coupling strategy due to the simplicity of starting materials, [17] and we herein describe the Pd-catalyzed construction of thiophene-fused COTf rameworks through the dehydrogenative cyclodimerization of 3,3'bithiophenes.T he method is applicable to various heteroaromatics,e nabling the facile synthesis of "composite" heteroarene-fused COTs (see below). [18] As et of mechanistic investigations suggested the involvement of palladacycle intermediates as well as high-valent Pd species in the catalytic cycle.…”

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Palladium‐Catalyzed Synthesis of Heteroarene‐Fused Cyclooctatetraenes through Dehydrogenative Cyclodimerization

2017

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Arene-fused cyclooctatetraenes (COTs) possess unique structural and electronic properties that originate from their saddle-shaped p-conjugated architectures.C onsiderable attention has been paid to the transition-metal-mediated synthesis of these cyclic compounds;however,there have been limited achievements to date in the efficient construction of heteroarene-fused COTs.I nt his contribution, we report an ovel Pd-catalyzed dehydrogenative cyclodimerization of biheteroarenes through four-fold CÀHa ctivation toward the synthesis of as eries of heteroarene-fused COTs.Aset of mechanistic investigations indicated the involvement of highvalent Pd species prior to the dimerization event in the catalytic cycle.T he redox behavior of the obtained COTs is also described briefly.

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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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Synthesis of Heterocyclic Cyclopolyaromatics Containing Different Kinds of Nuclei

Cited by 16 publications

References 5 publications

Palladium‐Catalyzed Synthesis of Heteroarene‐Fused Cyclooctatetraenes through Dehydrogenative Cyclodimerization

Palladium‐Catalyzed Synthesis of Heteroarene‐Fused Cyclooctatetraenes through Dehydrogenative Cyclodimerization

Palladium‐Catalyzed Synthesis of Heteroarene‐Fused Cyclooctatetraenes through Dehydrogenative Cyclodimerization

Heteroatom‐Facilitated Lithiations

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