TETRAHEDRON: ASYMMETRY Tetrahedron: Asymmetry 13 (2002) 607–613 Pergamon Hybrid silarylene polysiloxanes incorporating chiral BINOL entities: a new class of polymer with main chain chirality Peter Hesemann, Joe ¨l J. E. Moreau* and Cheng Yixiang He ´te ´rochimie Mole ´culaire et Macromole ´culaire, UMR CNRS 5076, Laboratoire de Chimie Organome ´tallique Ecole Nationale Supe ´rieure de Chimie de Montpellier, 34296 Montpellier Cedex 05, France Received 11 March 2002; accepted 19 March 2002 Abstract—We describe the synthesis of four new chiral silylated (R )-BINOL precursors by coupling of lithiated BINOL intermediates with chlorosilanes. These chiral precursors were submitted to different polycondensation procedures to give silarylene polysiloxanes A–D with main chain chirality: either by hydrolysis–polycondensation of the bis-chlorosilane precursor I or by Pd-catalyzed cross-dehydrocoupling of bis-hydrosilanes II, III and IV. Both monomers and polymers were characterized by NMR, FT-IR, circular dichroism and polarimetry. Polymers with molecular weights of up to 30,200 gmol -1 were obtained. © 2002 Elsevier Science Ltd. All rights reserved. 1. Introduction Functional polymers bearing chiral moieties have attracted considerable interest during the past decade. 1 The enantiodifferentiation properties of such macro- molecules give rise to multiple applications in the fields of asymmetric catalysis and molecular recognition. In particular, the elaboration of polymers with main chain chirality is a field of intense research activity. 2 In this kind of polymer, multiple chiral units are linked together to form a chiral polymer backbone. Control of the tacticity of polyolefins, which has been achieved elegantly by stereospecific polymerisation using chiral metallocene catalysts has attracted particular interest. 3 In contrast to asymmetric polymerisation reactions, a large variety of chiral main chain polyamides, polyureas, 4 polyesters, 5 and polypeptides 6 have been obtained by polycondensation reactions from chiral monomers. Polymers with main chain chirality have been used successfully as chiral auxiliaries in asymmet- ric catalysis 7–9 and for molecular recognition. 10 Poly- mers containing C 2 -symmetric binaphthyl units have been investigated. 11 2,2-Dihydroxy-1,1-binaphthol (BINOL) often serves as the starting material for obtaining chiral binaphthyl compounds, as the 2,2- hydroxyl groups of BINOL can be easily converted into other functional groups (ethers, esters, etc.) and the 3,3-, 4,4- and 6,6-positions of BINOL can selectively be functionalized, leading to a variety of binaphthyl derivatives bearing polymerisable groups. This approach gives rise to BINOL-derived polymers with unique structures and properties. Besides the excellent chiral induction in asymmetric catalysis and enan- tiorecognition properties, these polymers have been shown to be interesting materials for applications in the fields of optical nonlinearity and polarized lumines- cence. 11b Furthermore, chiral binaphthyl-based main chain polymers offer the possibility to control the sec- ondary structure of the macromolecule. Thus, chiral binaphthyl units have been shown to induce a heli- coidal secondary structure in linear polymers. 12 As part of our continuing interest in polymers and materials with defined architecture at the nano- and mesoscopic scale, 13 we focused on the synthesis of linear polymers with controlled secondary structure. In the present work, we investigated the synthesis of silarylene polysiloxanes [(O-(Me) 2 Si-Ar-Si) n ] (‘hybrid silicones’, polycarbosiloxanes) incorporating chiral BINOL units in the main chain. Hybrid silicones exhibit interesting properties due to the direct linkage between the organic and siloxane (–Si–O–Si–) segments in the polymer backbone and are useful materials for the elaboration of elastomers, membranes and coat- ings. 14–16 We believe that silarylene polysiloxanes are also promising candidates for the synthesis of linear * Corresponding author. Tel.: 33 (0)4 67 14 72 11; fax: 33 (0)4 67 14 72 12; e-mail: jmoreau@cit.enscm.fr 0957-4166/02/$ - see front matter © 2002 Elsevier Science Ltd. All rights reserved. PII:S0957-4166(02)00146-5