An efficient synthesis of novel spiro[[8H]indeno[2,1-b]-thiophene-8,9 0 -fluorene] building block for blue light-emitting materials Ling-Hai Xie, a Ting Fu, a Xiao-Ya Hou, a Chao Tang, a Yu-Ran Hua, a Rui-Jie Wang, a Qu-Li Fan, a Bo Peng, a Wei Wei a and Wei Huang a,b, * a Institute of Advanced Materials (IAM), Fudan University, 220 Handan Road, Shanghai 200433, People’s Republic of China b Faculty of Engineering, National University of Singapore, 9 Engineering Drive 1, Singapore 117576, Republic of Singapore Received 17 March 2006; revised 23 June 2006; accepted 26 June 2006 Abstract—We have developed efficient synthetic routes to obtain a novel building block spiro[[8H]indeno[2,1-b]thiophene-8,9 0 - fluorene] (SITF), a monothiophene-containing spirobifluorene analogue, and constructed blue light-emitting materials, including 2 0 ,7 0 -bis([1,1 0 -biphenyl]-4-yl)-spiro[indeno[2,1-b]thiophene-8,9 0 -fluorene] (BBP–SITF) and 2 0 ,7 0 -bis(9,9 0 -spirobifluoren-2-yl)spiro- [[8H]indeno[2,1-b]-thiophene-8,9 0 -fluorene] (BSBF–SITF). BSBF–SITF has shown to be a stable blue light-emitting material with high PL quantum efficiency (89%) and unique regioselective feature at the C2 of thiophene, which indicate that BSBF–SITF will be useful for constructing complicated optoelectronic systems. Ó 2006 Elsevier Ltd. All rights reserved. Organic p-conjugated materials continue to attract con- siderable interest because of their potential applications in various optoelectronic devices, especially in organic light-emitting diodes (OLEDs). 1 Since Tour and co- workers early introduced spirobifluorene unit into organic electronics in 1996, 2 spirobifluorene-containing oligomers and polymers are becoming promising candi- dates for electroluminescent materials due to their high luminescence efficiency, carrier mobility, as well as excel- lent thermal stability. Salbeck et al. exploited spirobiflu- orene building blocks to construct various oligomers. 3 Fully spiro-configured terfluorenes, monodisperse spirobifluorene trimmers and spirobifluorene-linked anthracene have also been synthesized and used as blue light-emitting materials with high thermal stability. 4 Carrier-transporting materials of spirobifluorene with high T g temperature show excellent nondispersive hole transporting and ambipolar carrier transporting proper- ties. 5 Our group firstly introduced the spirobifluorene unit into p-conjugated polymers to enhance the morphological stability in film states and to demonstrate the increase of thermally spectral stability. 6 In addition, spirobifluorene derivatives have also been applied to solar cells, organic phototransistors, NLO and laser materials. 7 However, the disadvantage of this kind of oligomers is the difficulty to tune the electronic structure and incorporate other functional groups, which greatly limits their applications in the field of organic electronics and construction of complicated optoelectronic systems. Incorporating heteroaryl groups, for example, thio- phene, pyridine, carbazole, into spiro compounds will be a useful strategy to expand the application of spiro compounds. However, so far, spiro compounds with heteroaryl groups have seldom been reported. 8 To ex- plore the complicated light-emitting system and gain better insight into the effect of spiro-substituted moieties on the electronic structures, in this contribution, we present the design and synthesis of a novel thiophene- containing ter(9,9 0 -spirobifluorene)s analogue with reg- ioselective features, and the investigation of absorption and emission spectra as well as electrochemical proper- ties as blue light-emitting materials. To successfully synthesize spiroindenothiophenefluorene (SITF), it is necessary to concurrently consider three 0040-4039/$ - see front matter Ó 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.tetlet.2006.06.143 Keywords: Spiro compounds; Spiroindenothiophenefluorene; Blue light-emitting materials; BF 3 ÆEt 2 O. * Corresponding author. Tel.: +86 21 5566 4188/4198; fax: +86 21 6565 5123; e-mail addresses: wei-huang@fudan.edu.cn; chehw@nus. edu.sg Tetrahedron Letters 47 (2006) 6421–6424