Synthese von Materialien mit erweitertem π‐System durch C‐H‐Aktivierung

Abstract

Die Aktivierung von aromatischen C‐H‐Bindungen durch einen Übergangsmetallkatalysator ist ein wichtiges Thema in der Synthesechemie. In den letzten Jahren hat sich die schnelle und regiospezifische Erweiterung von π‐Systemen durch C‐H‐Aktivierung zu einer idealen Methode zur Herstellung von organischen Materialien mit ausgedehntem π‐System entwickelt. Dieser Aufsatz fasst neuere Reaktionen zur C‐H‐Aktivierung für die Erweiterung von π‐Systemen im Hinblick auf neue optoelektronische konjugierte Materialien zusammen.

Iridium‐Catalyzed Annulation Reactions of Thiophenes with Carboxylic Acids: Direct Evidence for a Heck‐type Pathway

“…[2] Thus their highly efficient synthesis has attracted considerable attention. [4] Our group lately demonstrated the fusion of athiophene ring to af unctionalized (hetero)arene,s uch as aniline,o rbenzoic acid through stepwise CÀH/CÀHc ross-coupling and intramolecular cyclization, to afford as eries of thiophene-fused polyheterocycles (Scheme 1a). [3] Recently,t he development of C À H activation strategies for the construction of p-conjugated polyheterocycles has become an area of intense research.…”

“…Benzothiophenes with electron-withdrawing (Cl and Br) or electron-donating (methoxy and phenyl) groups underwent this reaction in excellent yields (4a-4e). With 4,thiophene,thieno [3,2-b]thiophene,and benzo [1,2-b:4,5-b']dithiophene as the coupling partner,t he desired products were obtained in moderate yields (4j-4l). With 4,thiophene,thieno [3,2-b]thiophene,and benzo [1,2-b:4,5-b']dithiophene as the coupling partner,t he desired products were obtained in moderate yields (4j-4l).…”

Metal‐Free Dehydrogenative Diels–Alder Reactions of 2‐Methyl‐3‐Alkylindoles with Dienophiles: Rapid Access to Tetrahydrocarbazoles, Carbazoles, and Heteroacenes

“…[7,8] To advance organic materials science,t he design of novel scaffolds and improvements in synthetic methods for these compounds are critically important. Obviously,t hose methodologies which are based on direct CÀHf unctionalization have advantages over the classic reactions as they do not require the prefunctionalization of starting materials.H owever,d espite the progress made in the synthesis of extended p systems by direct C(sp 2 ) À Ha ctivation, [9] thed evelopment of novel methodologies through direct C(sp 3 ) À Hf unctionalization still remain ac onsiderable challenge.D uring our recent endeavors directed toward in situ generation of heterocyclebased ortho-quinodimethanes (oQDMs) [10] via ac ascade process consisting of C(sp 3 )ÀHfunctionalization, [11] we envisScheme 1. Previous work and this work with ap rojected working hypothesis.…”

Metal‐Free Dehydrogenative Diels–Alder Reactions of 2‐Methyl‐3‐Alkylindoles with Dienophiles: Rapid Access to Tetrahydrocarbazoles, Carbazoles, and Heteroacenes

“…[6] Meanwhile,carbazoles and derivatives have received considerable attention because of their frequent occurrence in biologically active natural and unnatural products,a nd in organic functional materials ( Figure 1). Obviously,t hose methodologies which are based on direct CÀHf unctionalization have advantages over the classic reactions as they do not require the prefunctionalization of starting materials.H owever,d espite the progress made in the synthesis of extended p systems by direct C(sp 2 ) À Ha ctivation, [9] thed evelopment of novel methodologies through direct C(sp 3 ) À Hf unctionalization still remain ac onsiderable challenge.D uring our recent endeavors directed toward in situ generation of heterocyclebased ortho-quinodimethanes (oQDMs) [10] via ac ascade process consisting of C(sp 3 )ÀHfunctionalization, [11] we envis-Scheme 1. Obviously,t hose methodologies which are based on direct CÀHf unctionalization have advantages over the classic reactions as they do not require the prefunctionalization of starting materials.H owever,d espite the progress made in the synthesis of extended p systems by direct C(sp 2 ) À Ha ctivation, [9] thed evelopment of novel methodologies through direct C(sp 3 ) À Hf unctionalization still remain ac onsiderable challenge.D uring our recent endeavors directed toward in situ generation of heterocyclebased ortho-quinodimethanes (oQDMs) [10] via ac ascade process consisting of C(sp 3 )ÀHfunctionalization, [11] we envis-Scheme 1.…”

“…[7,8] To advance organic materials science,t he design of novel scaffolds and improvements in synthetic methods for these compounds are critically important. Obviously,t hose methodologies which are based on direct CÀHf unctionalization have advantages over the classic reactions as they do not require the prefunctionalization of starting materials.H owever,d espite the progress made in the synthesis of extended p systems by direct C(sp 2 ) À Ha ctivation, [9] thed evelopment of novel methodologies through direct C(sp 3 ) À Hf unctionalization still remain ac onsiderable challenge.D uring our recent endeavors directed toward in situ generation of heterocyclebased ortho-quinodimethanes (oQDMs) [10] via ac ascade process consisting of C(sp 3 )ÀHfunctionalization, [11] we envis- aged that the indole-based oQDM [12] B might be generated in situ from 2-methyl-3-arylmethylindolesb yaDDQ-mediated dehydrogenative process for direct C(sp 3 ) À Hf unctionalizations.I nt he presence of suitable dienophiles,asubsequent Diels-Alder cycloaddition might take place.I ft his hypothesis is successful, it will provide rapid access to various synthetically valuable tetrahydrocarbazoles,c arbazoles,a nd poly-heteroacenes from readily available starting materials in an efficient manner.…”