The syntheses of polyethynyl-substituted 2,2'-bithiophenes 2 and related 5,5'-dicarbaldehyde derivatives 1 are described. The treatment of easily available polybrominated 2,2'-bithiophenes 3 and 2,2'-bithiophene-5,5'-dicarbaldehydes 4 with phenyl or (trimethylsily1)acetylene in the presence of Pd" and Cut in (i-Pr)*NH yields substituted polyethynyl-2,2'-bithiophene compounds. The Me$i protecting groups can be removed by protodesilylation under basic conditions to give the corresponding terminal ethynyl groups. These polyethynyl-bithiophenes could be interesting precursors for the synthesis of macrocycles with interesting properties.Introduction. -The development of new synthetic strategies for the syntheses of porphyrins, porphycenes, and related conjugated macrocycles has recently received much attention because of their special aromatic properties as annulene derivatives [ 11 as well as their potential for use as photosensitizers [2]. There have been a number of investigations in the recent past concerning the use of porphyrins for biomedical applications such as fluorescence detection, viral inhibition [3], and photodynamic tumor therapy (PDT) [4].Many attempts have been made to modify the porphyrin ring system to create new chromophores. Inverted [5] and expanded porphyrinoides [6] as well as porphycenes, hemiporphycenes, and corrphycenes [7] have been synthesized. Heterocyclic analogs of this class of compounds have also been reported [8].Prompted by the observation of Vogel, Schaffner and coworkers [9], which showed the potential of acetylenic and cumulenic porphycene derivatives as PDT agents, we investigated the syntheses of S-containing porphycene analogs, namely 21,23-dithiaporphycene and tetrathiaporphycene [ 101. The 2,2'-bithiophenes ( = 2,2'-bithienyls), the major component of the thiaporphycene system, have also been reported to possess interesting properties. Naturally occurring bithiophenes, specifically acetylenic derivatives, show nematolocidal, as well as antibiotic, ovicidal, algicidal, larvicidal, and antifeedant properties [ 1 11. These 2,2'-bithiophene compounds have also been shown to inhibit germination and cell growth [12] and are phototoxic to some aquatic organisms [13]. By combining the properties found in porphycenes and those found in alkynyl-substituted bithiophenes, alkynylated thiaporphycenes should produce a group of macrocycles with high biological activity.Presently, the most efficient route to porphycenes and analogous systems involves the intermolecular dimerization of carbonyl compounds with low-valent titanium, the socalled McMuvry reaction [7] [lo] [14]. We planned to apply this methodology to the

The syntheses of benzo‐fused benzo[2, 1‐b:3, 4‐b′]dithiophenes 1 and benzo[2, 1‐b:3, 4‐b′:5, 6‐c″]trithiophenes 2 are described. The treatment of easily available 3, 3′‐bis(phenylethynyl)‐2, 2′‐bithiophene derivatives 5a and 6 (via PdII‐catalyzed alkynylation of the corresponding 3, 3′‐dibromo‐2, 2′‐bithiophenes; see Scheme 1) with chlorotris‐(triphenylphosphine)rhodium(I) yields the corresponding cyclic rhodium complexes 7 (Scheme 2) which smoothly react with acetylenes and sulfur to give 1 and 2 in good yields (Schemes 3–5).

The title compounds, in which the terminal alkyne functions are adorned with -CH2OCH2CH2OCH2CH2OCH2CH3 or -p-C6H4OCH2CH2 OCH2CH2OCH3 substituents, were synthesized. The strategies for their preparation relied on prior art and involved the use of Sonogashira alkynylations of appropriate haloarenes, Stephens–Castro cyclizations of 1,2,4-trialkynyl-3-iodobenzenes, and Hay oxidative couplings of 1,2,3,4-tetralkynylbenzenes. The targets form yellow materials, exhibiting yellow-green fluorescence, and they are very soluble in polar solvents, but only sparingly so in nonpolar media. Attempts to convert them into the antikekulene frame through CpCo(CO)2-catalyzed (co)-cyclizations failed.

The syntheses of tetraalkynylated tetrasulfido[20]annulenes 2a−d are described. Treatment of the corresponding brominated tetrasulfido[20]annulene 5a (easily available by McMurry coupling of the brominated 2,2′‐bithiophene‐5,5′‐dicarbaldehydes, 3a) with various acetylenes in the presence of Pd(II) and Cu(I) in NH(iPr)2 yields acetylenic tetrasulfido[20]annulenes 2a−d.

The syntheses of tetraalkynylated tetrasulfido [20]annulenes dicarbaldehydes, 3a) with various acetylenes in the presence of Pd(II) and Cu(I) in NH(iPr) 2 yields acetylenic tetrasulfi2aϪd are described. Treatment of the corresponding brominated tetrasulfido [20]annulene 5a (easily available by do [20]annulenes 2aϪd. McMurry coupling of the brominated 2,2Ј-bithiophene-5,5Ј-The syntheses of novel porphyrins, porphycenes, and re-antifeedant properties and are phototoxic to some aquatic organisms [5] . Thus, we became interested in the synthesis of lated conjugated macrocycles are currently the subject of active investigations inter alia for their potential as photo-alkynylated 1, 4:5,8:11,14:15,18-tetrasulfido[20]annulenes 2 in order to combine the properties found in porphycenes sensitizers for biomedical applications [1] such as fluorescence detection, viral inhibition and photodynamic tumor and those found in alkynylsubstituted bithiophenes for an approach to a group of macrocycles with high biological actherapy (PDT). In the recent past many attempts have been made to modify the porphyrin ring system to create new tivity. chromophores [2] . Prompted by the fundamental work of The intermolecular reductive coupling of dicarbonyl Vogel and co-workers, who demonstrated the potential use compounds with low-valency titanium under McMurry of porphycenes and some of their acetylenic derivatives as conditions [6] has been established as the most efficient PDT agents [3] , we investigated the synthesis of sulfur-con-methodology for the preparation of porphycenes and analtaining porphycene analogs 1 and observed remarkable ogous systems[2a] [7] . Indeed, we have previously reported changes in the structural and chemical properties of these the synthesis of alkynylated 2,2Ј-bithiophene-5,5Ј-dicarbcompounds [4] . aldehydes [8] , which should be suitable precursors for a McMurry-type cyclisation. However, their dimerisation to Scheme 1 the target molecules 2 failed. We therefore decided first to cyclize the brominated 2,2Ј-bithiophene-5,5Ј-carbaldehydes 3 and then alkynylate the resulting brominated 1,4:5,8:11,14:15,18-tetrasulfido[20]annulenes 5 by palladium(0)-catalyzed procedures [8] [9] .First attempts at the reductive dimerisation of compounds 3 involved reaction conditions used in the synthesis of the unsubstituted tetrasulfido [20]annulene 1 (X ϭ S) as previously reported [4b] . According to this procedure the coupling of 4,4Ј-dibromo-2,2Ј-bithiophene-5,5Ј-dicarbaldehyde (3a) with low-valency titanium prepared by treatment of TiCl 4 with Zn/Cu pair in the presence of pyridine in THF proceeds under high-dilution conditions and gives, after workup with ammonia, the 2,7,12,17-tetrabromo-9,10-2,2Ј-Bithiophenes, the major structural component of the dihydro-1,4:5,8:11,14:15,18-tetrasulfido[20]annulene (4) in a thiaporphycene skeleton, have been reported as possessing yield of 9% (Scheme 2). interesting biological activities. Naturally occurring bithiophenes, specifically acetylenic derivatives, show nematoci-The format...