π-Extended Phosphepines: Redox and Optically Active P-Heterocycles with Nonplanar Framework

Abstract

In this letter, we present the synthesis of a new family of -extended dithieno[b,f]phosphepines. The Pd-catalyzed direct-arylation allows the introduction of various substituents, which tune the absorption/emission in the visible range as well as the redox properties. All those modifications were rationalized through DFT calculations. The physical properties of ambipolar phosphepine with diphenylamino substituents conduct us to use it as a semiconductor in a p-type organic field-effect transistors (OFETs).

Isomeric Dithienophosphepines: The Impact of Ring Fusion on Electronic and Structural Properties

“…DTP oxide 5β adopts a different conformation than the other DTPs with its oxygen atom being oriented almost perpendicular to the DTP backbone ( anti conformation). These features agree with those of the crystal structure reported for the same compound by Delouche et al . In contrast, the lone pairs, borane units, and oxo groups, respectively, are pointing in the same spatial direction as the thiophenes ( syn conformation) in case of all other derivatives.…”

“…Very recently, Delouche et al. reported on the direct Pd‐catalyzed arylation of 5β , however, we found that this approach is not applicable to the corresponding α‐isomer. Instead, we were able to introduce phenylethynyl units through direct C−H functionalization of thiophene.…”

“…Both scaffolds have been reported previously, however, no photophysical and electrochemical investigations of 1α have been described . Moreover, β‐DTP was only isolated as pentavalent phosphine oxide . With this work, we therefore provide a reliable and scalable synthesis of trivalent and pentavalent DTPs and discuss the influence of the isomerically different ring fusions on the electronic and structural properties of these compounds.…”

“…[6b] Moreover, b-DTP was only isolated as pentavalent phosphine oxide. [10] With this work, we therefore provide ar eliable and scalables ynthesis of trivalent and pentavalent DTPs and discuss the influence of the isomerically different ring fusions on the electronic and structural properties of thesec ompounds. Additionally,w ee xplored the possibilities of post-functionalization at the thiophenem oieties to achieve novel p-expanded DTPs.…”

“…Unfortunately,b oth routes showed to be unsuitable for our DTPs with the exception of borane adduct 4b, which allowed for the introduction of bromines and formyl groups at the a-position of thiophene through treatment with tBuLi and subsequent quenching with elemental bromine and DMF,r espectively (compounds S1 and S2 in the Supporting Information).A lthough both functionalities should in principle allow for subsequent derivatization, we did not pursue this approach any furthera nd turned our attention towards more straightforward methods such as direct oxidative cross-couplings. Very recently,D elouche et al reported on the direct Pdcatalyzed arylation of 5b, [10] however,w ef ound that this approach is not applicable to the corresponding a-isomer.I nstead, we were able to introduce phenylethynyl units through direct CÀHf unctionalization of thiophene. Suitable conditions (Pd 2 (dba) 3 ,P ivOH, Cs 2 CO 3 ,E t 3 N, Ag 2 Oi nD ME at 100 8C) [9a] were adaptedf rom Jie et al and afforded the desired ethynylated DTP oxides 6a and 6b in over 40 %yield (Scheme 3).…”