Synthesis of some mono and dialkynyl derivatives containing thieno thiophene ring via sonogashira alkynylation reaction

The Sonogashira cross-coupling reactions were used to synthesize 5 new monoalkynyl derivatives (10a-e) and 2 dialkynyl derivatives (12a-b) containing thieno[3,2-b]thiophene from monoaryl thieno[3,2-b]thiophen in moderate yield. The procedure was optimized and triphenylphosphine (0.2 eq.), palladium diacetate (0.1 eq), copper (I) iodide (0.2 eq.), THF, iPr2NH were found to be the best in these cases. The structures of the (10a-e) and (12a-b) compounds were elucidated by 1H and 13C NMR and mass spectral analysis.
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Synthesis of some mono and dialkynyl derivatives containing thieno thiophene ring via sonogashira alkynylation reactionTRƯỜNG ĐẠI HỌC SƯ PHẠM TP HỒ CHÍ MINHHO CHI MINH CITY UNIVERSITY OF EDUCATIONTẠP CHÍ KHOA HỌCJOURNAL OF SCIENCEKHOA HỌC TỰ NHIÊN VÀ CÔNG NGHỆNATURAL SCIENCES AND TECHNOLOGYISSN:1859-3100 Tập 14, Số 9 (2017): 85-93Vol. 14, No. 9 (2017): 85-93Email: tapchikhoahoc@hcmue.edu.vn; Website: http://tckh.hcmue.edu.vnSYNTHESIS OF SOME MONO AND DIALKYNYL DERIVATIVESCONTAINING THIENO[3,2-b]THIOPHENE RING VIASONOGASHIRA ALKYNYLATION REACTIONNguyen Hien, Duong Quoc Hoan*Department of Chemistry - Hanoi National University of EducationReceived: 28/7/2017; Revised: 23/8/2017; Accepted: 23/9/2017ABSTRACTThe Sonogashira cross-coupling reactions were used to synthesize 5 new monoalkynylderivatives (10a-e) and 2 dialkynyl derivatives (12a-b) containing thieno[3,2-b]thiophene frommonoaryl thieno[3,2-b]thiophen in moderate yield. The procedure was optimized andtriphenylphosphine (0.2 eq.), palladium diacetate (0.1 eq), copper (I) iodide (0.2 eq.), THF, iPr2NHwere found to be the best in these cases. The structures of the (10a-e) and (12a-b) compounds wereelucidated by 1H and 13C NMR and mass spectral analysis.Keywords: alkynylthiophene, cross-coupling reaction, monoarylthiophene, Sonogashirareaction, thieno[3,2-b]thiophene.TÓM TẮTTổng hợp một vài dẫn xuất monoankinyl và điankinyl có chứa vòng thieno[3,2-b]thiophenbằng phản ứng ghép chéo SonogashiraPhản ứng ghép chéo Sonogashira được dùng để tổng hợp được 5 dẫn xuất mới monoankin(10a-e) và 2 dẫn xuất điankin (12a-b) có chứa dị vòng thieno[3,2-b]thiophen với hiệu suất trungbình. Điều kiện phản ứng được nghiên cứu tối ưu hóa là triphenylphosphin (0.2 eq.), palađiđiaxetat (0.1 eq), đồng (I) iodide (0.2 eq.), THF, iPr2NH là điều kiện tốt cho phản ứng này. Cấutrúc của các hợp chất mới được nghiên cứu bằng phổ 1H, 13C NMR và phổ khối lượng.Từ khóa: ankinylthiophen, phản ứng ghép chéo, monoarylthiophen, phản ứngnSonogashira,thieno[3,2-b]thiophen.1.IntroductionThe small band gap of organic semiconducting polymers has been a challenge forscientists. To overcome this problem, extension of the π system by increasing theconjugated length of the molecule is one of the most efficient approaches. Thieno[3,2b]thiophene is a stable and electron-rich π-conjugated core with four carbon atoms that is a*Email:hoandq@hnue.edu.vn;85TẠP CHÍ KHOA HỌC - Trường ĐHSP TPHCMTập 14, Số 9 (2017): 85-93useful building block for the construction of organic semiconductors with differentconjugation lengths by extending the conjugation length. Shi et al. reported Sn-TIPS as anew high performance semiconductor; Figure 1 (left) [1].Figure 1. Structures of anti‐aromatic bisindeno‐thienoacenes Sn‐TIPS (n = 1‐4) and proaromaticbisphenaleno‐thieno[3,2‐b]thiophene BPT‐TIPS[1] andPd-catalyzed cross-coupling reactions ofsp2-C halides with terminal acetylenes and Outline of the reaction scheme for Pd–Cu catalyzedcross-coupling of sp2 -C halides with terminal acetylenes [2].By the same manner, McCulloch et al. synthesized liquid-crystalline semiconductingpolymer (PBTTT) containing thieno[3,2-b]thiophene moieties with a very high chargecarrier mobility [3]. Another example, dinaphtho[2,3-b:2′,3′-f]thieno[3,2-b]thiophene(DNTT) and alkylated benzothieno[3,2-b][1]benzothiophene (C13BTBT) were proved tobe an effective to make a very high thin film mobility of 3.1 cm2/Vs and 17.2 cm2/Vs,respectively, in VD-OFETs [4,5].One of the best tools to build the conjugation system is the Sonogashira reaction,which is a powerful method to make Csp–Csp2 bond [2, 6, 7]. Reaction and mechanismwere performed in Figure 1 (right) including three bases steps: i-oxidative addition; iitransmetalation, iii-reductive elimination. In this paper we were interested in usingSonogashira in making Csp-Csp2 bond based C-Br bond and -CC-H one betweenmonoalkylthiophene and alkynes.2.Experimental2.1. Experimental sectionSolvents and other chemicals were purchased from Sigma-Aldrich, Merck were used asreceived, unless indicated. The 1H NMR and 13C NMR spectra were recorded on theBruker Avance 500 NMR spectrometer in CDCl3. Chemical-shift data for each signal was86TẠP CHÍ KHOA HỌC - Trường ĐHSP TPHCMNguyen Hien et al.reported in ppm units. Mass spectra were obtained from Mass Spectrometry Facility of TheVietnam Academy of Science and Technology on LC-MSD-Trap-SL spectrometer.2.2. Synthetic procedureGeneral procedure:To the argon degassed solution of THF (6 mL) and iPr2 NH (6 mL) was added 2,3,6tribromo-5-(1,2-dihydroacenaphthylen-6-yl)thieno[3,2-b]thiophene or 2,3,6-tribromo-5(naphthalen-1-yl)thieno[3,2-b]thiophene (0.25 mmol, 1 eq.), Ph3P (13.1 mg, 0.05 mmol,0.2 eq., 262 g/mol), Pd(OAc)2 (5.6 mg, 0.025 mmol, 0.1 eq., 224 g/mol), CuI (10 mg, 0.05mmol, 0.2 eq., 190 g/mol). The resulting solution was refluxed to d ...