Advances in the synthesis of functionalised pyrrolotetrathiafulvalenes

Abstract

SummaryThe electron-donor and unique redox properties of the tetrathiafulvalene (TTF, 1) moiety have led to diverse applications in many areas of chemistry. Monopyrrolotetrathiafulvalenes (MPTTFs, 4) and bispyrrolotetrathiafulvalenes (BPTTFs, 5) are useful structural motifs and have found widespread use in fields such as supramolecular chemistry and molecular electronics. Protocols enabling the synthesis of functionalised MPTTFs and BPTTFs are therefore of broad interest. Herein, we present the synthesis of a range of functionalised MPTTF and BPTTF species. Firstly, the large-scale preparation of the precursor species N-tosyl-(1,3)-dithiolo[4,5-c]pyrrole-2-one (6) is described, as well as the synthesis of the analogue N-tosyl-4,6-dimethyl-(1,3)-dithiolo[4,5-c]pyrrole-2-one (7). Thereafter, we show how 6 and 7 can be used to prepare BPTTFs using homocoupling reactions and functionalised MPTTFs using cross-coupling reactions with a variety of 1,3-dithiole-2-thiones (19). Subsequently, the incorporation of more complex functionality is discussed. We show how the 2-cyanoethyl protecting group can be used to afford MPTTFs functionalised with thioethers, exemplified by a series of ethylene glycol derivatives. Additionally, the merits of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) as an alternative to the most common deprotecting agent, CsOH·H2O are discussed. Finally, we show how a copper-mediated Ullman-type reaction can be applied to the N-arylation of MPTTFs and BPTTFs using a variety of aryl halides.

Probing the Electrostatic Barrier of Tetrathiafulvalene Dications using a Tetra‐stable Donor–Acceptor [2]Rotaxane

“…This procedure generated the monothiolate, which was alkylated with the iodide 3 carrying the bulky stopper unit to give the TTF derivative 4 in 48 % yield. The pseudo‐dumbbell 5 was detosylated by heating it under reflux in a 1:1 mixture of THF and MeOH in the presence of excess NaOMe to produce compound 6 , which was immediately N‐alkylated (NaH/DMF) with an excess of 1,2‐bis(2‐iodoethoxy)ethane, affording compound 7 in an overall yield of 75 %. Subsequently, 7 was coupled to the TTF derivative 4 , following its in situ deprotection with 1,8‐diazabicyclo‐[5,4,0]undec‐7‐ene (DBU) in THF, to provide (56 %) the dumbbell 8 .…”

“…All commercial reagents were standard grade and used as received. 2,6‐Bis(2‐cyanoethylthio)‐3,7‐bis(methylthio)tetrathiafulvalene ( 2 ), 2‐(2‐(2‐[4‐(tris(4‐ tert‐ butylphenyl)methyl)phenoxy]ethoxy)ethoxy)ethyl‐iodide ( 3 ), compound 5 , and 1,1’‐[1,4‐phenylene‐bis(methylene)]bis(4,4’‐bipyridinium)bis(hexafluorophosphate) ( 9 ⋅2PF 6 ) were all prepared according to literature procedures. Analytical thin layer chromatography (TLC) was performed on Merck DC‐Alufolien Kiselgel 60 F254 0.2 mm thickness precoated TLC plates, while column chromatography was performed using Merck Kiselgel 60 (0.040–0.063 mm, 230–400 mesh AST0000M).…”

Synthesis and Characterization of Ethylenedithio-MPTTF-PTM Radical Dyad as a Potential Neutral Radical Conductor

“…All reagents and solvents employed for the syntheses were of high purity grade and were purchased from Sigma-Aldrich Co. (St Louis, MO, USA), Merck (Darmstadt, Germany), and SDS, except compound 3 [18] and 4 [19] which were synthesized according to literature procedures Anhydrous solvents were used in the chemical reactions and for recording the cyclic voltammograms. 1 H NMR spectra were recorded using a Bruker Avance 250, 400, or 500 instruments (Bruker, Billerica, MA, USA) and Me 4 Si was used an internal standard.…”

“…First, the cross-coupling of the ethylendithio-thione (3) [18] and 5-tosyl-(1,3)-dithiolo [4,5-c]pyrrole-2-one (4) [19] in anhydrous (EtO) 3 P gave 5 in 82% yield after column chromatography. Subsequently, the tosyl protecting group on derivative 5 was removed using NaOMe in a THF/MeOH mixture to obtain compound 6 as a yellow solid which was used in the next reaction without further purification.…”

Synthesis and Characterization of Ethylenedithio-MPTTF-PTM Radical Dyad as a Potential Neutral Radical Conductor

“…The synthesis of the aldehyde precursor 7 was carried out as outline in Scheme 2. First, the crosscoupling of the ethylendithio-thione (3) [17] and 5-tosyl-(1,3)-dithiolo [4,5-c]pyrrole-2-one (4) [18] in anhydrous (EtO)3P gave 5 in 82% yield after column chromatography. Subsequently, the tosyl protecting group on derivative 5 was removed using NaOMe in a THF/MeOH mixture to obtain compound 6 as a yellow solid which was used in the next reaction without further purification.…”