Dithieno thiophene, synthesis

Synthesis of dithieno[2,3-A2,3-,7]thiophene derivatives 122 has been accomplished through the Heck reaction of 3-(4-bromo-2-thienyl)acrylic acid 302 to afford 3-(2,4-thienylene)diacrylic acid 303 which was cyclized with thionyl chloride and a catalytic amount of pyridine to the dichloride 120 in 75% yield (Scheme 56) <2005MOL279>. 

An improved synthesis of dithieno[3,2-A2, 3 -<7]thiophene 15a has been achieved from 2,3-dibromothiophene 304 (Scheme 57). Lithiation of 2,3-dibromothiophene 304 using -butyllithium followed by oxidative coupling with cupric chloride provided 3,3 -dibromo-2,2 -bithiophene 305 in 79% yield. Treatment of 305 with 2 equiv of -butyllithium in ether at —78 °C under nitrogen for 40 min and then adding benzenesulfonic acid thioanhydride and leaving the reaction mixture to reach room temperature afforded dithieno[3,2-A2, 3 -<7]thiophene 15a in 70% yield <2002TL1553>. 

The synthesis of dithieno[3,2-3 2, 3 -<7]thiophene 15a has also been accomplished using a combination of the methods described by De Jong et al. and Brandsma . In this approach, 3-bromothiophene 298 was lithiated and the 3-lithiothiophene 308 species reacted with sulfur dichloride to give di(3-thienyl)sulfide 309. Ring closure of 309 was effected using -butyllithium followed by addition of cupric chloride to yield dithieno[3,2-3 2, 3 -. 

A general synthesis of dibenzo-annelated dithieno[3,Z-b Z, 3 - thiophene 18 has been reported from bis(o-hydro-xyl)diacetylenes. This cyclization constructs a fused tricyclic skeleton in one pot. The subsequent dechalconization with copper powder produces a series of thiophene and selenophene-based heterocenes (Scheme 64) <20050L5301>. 

The synthesis, characterization, electrical conductivity, and field effect mobility of a series of novel soluble N-alkyl dithieno[3,2-b 2, 3 -d]pyrrole (DTP) and thiophene (TH)-based copolymers (DTP-co-THs) were reported (06MM1771 08JA13167). The incorporation of DTP units extends n conjugation, and the introduction of thiophene subunits imparts good solubility, high conductivity, and high charge carrier mobility. Therefore, the incorporation of DTP units and various substituted thiophenes into the polymer backbone affords the ability to enhance the solubility, lower the band gap, and achieve the enhanced electronic properties. 

The use of thienyl Grignard reagents, and more recently lithiated thiophenes, has been extensive and can be illustrated by citing formation of oxythiophenes, either by reaction of the former with f-butyl perbenzoate or the latter directly with bis(trimethylsilyl) peroxide or via the boronic acid, the synthesis of thiophene carboxylic acids by reaction of the organometallic with carbon dioxide, the synthesis of ketones, by reaction with a nitrile, or alcohols by reaction with aldehydes, by the reaction of 2-lithiothiophene with A -tosylaziridine, and by syntheses of thieno[3,2- ]thiophene and of dithieno[3,2- 2, 3 - /]thiophene. Some of these are illustrated below. 

Three approaches to the synthesis of dithieno[2,3-Z) 3, 2 -J]thiophene (10) and dithieno[3,4-Zr 3, 4 -r thiophene (11) starting from di(bromothienyl) sulfides 8 and 9 were developed (97TL4581, 2000H761). One procedure (condensation a) involves cyclization of sulfides 8 and 9 with hexamethyldistannane catalysed by a palladium complex. Two other procedures involve lithiation, the formation of organocopper (conditions b, c, e) or organozinc (conditions b, d, e) derivatives and their oxidation by molecular oxygen. 

Route 1 involves an initial migratory arylzincation pathtvay that is followed by a copper-mediated reaction with elemental sulfur, with accompanying C-S cyclization to afford a substituted benzothiophene in a one-pot reaction. Alternatively, in route 2, the zinc intermediate is first trapped by iodine, and subsequent copper-catalyst allows C-S/C-Se bond formation followed by cyclization in the presence of elemental sulfur or selenium to afford the corresponding benzochalcogenophene. A modular two-step synthesis of dithieno[3,2-l) 2, 3 -d]thiophene derivatives by C-S cross-coupling and oxidative dehydro C-H coupHng was also described in the year 2014 (14OL4086). 

M. Miyasaka and A. Rajca, Synthesis of dithieno[2,3-fc 3, 2 -<7]thiophenes - building blocks for cross-conjugated beta-oligothiophenes, J. Org. Chem., 71, 3264-3266 (2006). 

Scheme 60 Synthesis of dithieno[3,2- 2, 3 -ii]thiophene (242) from 3-hromothiophene (5) [95]...

Synthesis of Oligomers of Dithieno[3,2-6 2 -[Pg.188]

Synthesis of Polymers Containing Dithieno[3 - 2 -[Pg.189]

A three-step synthesis of the DTT dithieno[2,3-b 2, 3 -ri]thiophene (245), started from 3-bromo-2-(thien-3-yl)thiophene (330) utilized bromination to 331, then treatment with n-BuLi and finally elemental sulfur producing 332 heating this thiol with CuO gave 245 (Scheme 83) [131],... 

The synthesis of DTT dithieno[3,4-f> 3, 2 -rf]thiophene (246) starts with the reaction of 3-bromo-2-lithiothiophene (313) with disulfide 333 to give 334. Dilithiation with n-BuLi and then oxidative ring closure using CuCl2 lead to 246 [95] (Scheme 84). DTT (246) has been eleclropolymerized [103,132]. 

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