pubs.acs.org/Macromolecules Published on Web 02/05/2010 r 2010 American Chemical Society Macromolecules 2010, 43, 2213–2218 2213 DOI: 10.1021/ma902792a Quick Access to Diverse Polymerizable Molecules (a Monomer Library) by Catalytic [2 þ 2 þ 2] Cycloaddition Reactions of Functionalized Alkynes Jun-ichi Watanabe, † Yu-ki Sugiyama, † Ayami Nomura, † Suzumi Azumatei, † Avijit Goswami, † Naoko Saino, ‡ and Sentaro Okamoto* ,† † Department of Material & Life Chemistry, Kanagawa University, 3-27-1 Rokkakubashi, Kanagawaku, Yokohama 221-8686, Japan, and ‡ New Products Development Division, Kanto Denka Kogyo Co., Ltd., 425 Kanai, Shibukawa, Gunma 377-0027, Japan Received December 18, 2009; Revised Manuscript Received January 22, 2010 ABSTRACT: The [2 þ 2 þ 2] cycloaddition reactions of 1,6-diynes and alkynes with a functional group(s), such as epoxide, oxetane, ester, alcohol, phenol, amine, borate, styrene, and methacrylate, catalyzed by a dipimp/ CoCl 2 3 6H 2 O/Zn reagent [dipimp: 2-(2,6-diisopropylphenyl)-iminomethyl-pyridine] yielded a variety of polymeri- zable molecules (monomers) having a 2,3-dihydro-1H-indene core structure. Similarly, the [2 þ 2 þ 2] cycloaddition reactions of 1,6-diynes and nitriles with a functional group(s) catalyzed by a dppe/CoCl 2 3 6H 2 O/ Zn reagent [dppe: 1,2-bis(diphenylphosphino)ethane] gave a variety of polymerizable molecules (monomers) with a 6,7-dihydro-5H-cyclopenta[c]pyridine core structure. Among the resulting monomers, 5-phenyl-1,3- dihydrospiro[indene-2,3 0 -oxetane] prepared from 3,3-di(prop-2-ynyl)oxetane and phenylacetylene was representa- tively polymerized in the presence of BF 3 catalyst. A cationic random copolymerization of one of 1,3-dihydrospiro- [indene-2,3 0 -oxetane] derivatives with 3-ethyl-3-(phenoxymethyl)oxetane and radical random copolymerization of diethyl 5-(4-vinylphenyl)-1H-indene-2,2(3H)-dicarboxylate with styrene have also been demonstrated. Introduction In the study of functional materials, polymer science is increasingly important. For bottom-up development of new functional polymers, the preparation of new polymerizable molecules (monomers) with functional handles for compositional versatility is desired. 1 In contrast to the conventional, individual preparation of monomers for planned polymerization, we propose a convergent process that couples simple molecules having a polymerizable functional group (PG) and a functional group(s) necessary for the desired properties of the resulting polymers, the synthesis of which enables a quick and easy access to diverse monomers (a monomer library) and the corresponding polymers. To realize this idea, the coupling reaction must have high functional group compatibility. In this context, Fr  echet and Hawker et al. have developed a synthesis of a variety of monomers comprised with a 4-vinyl-1,3,5-triazole structure by the Cu(I)-catalyzed cycloaddi- tion of azides and alkynes and demonstrated their radical poly- merizations. 2 Herein is reported synthesis of a wider range of polymerizable molecules of types 4 and 5 from diynes 1 with alkynes 2 or nitriles 3 by using a catalytic [2 þ 2 þ 2] cycloaddition reaction as the coupling process (Scheme 1). Attributed to molecular assembly by a combination of the starting alkynes and nitriles, various monomers 4 and 5 can be prepapred; their polymerization will give a variety of polymers such as types I, II, and III. Alternative copolymerization with a combination of these new monomers and also with conventional monomers might open a broad range of new polymer families. Results and Discussion Although a variety of functional groups tolerated under the reaction conditions of catalyzed [2 þ 2 þ 2] alkyne-cycloaddition reactions developed so far, 3 the compatibility of polymerizable functional groups (PGs) has not been investigated systematically. First, we explored the stability of such functional moieties under the conditions of the cycloaddition reaction catalyzed by a dipimp/CoCl 2 3 6H 2 O/Zn reagent [dipimp: 2-(2,6-diisopropyl- phenyl)-iminomethylpyridine] that we developed. 4 Thus, the cycloaddition reaction of diyne 1a with phenylacetylene (2a) catalyzed by a dipimp/CoCl 2 3 6H 2 O/Zn reagent was carried out in the presence of the model molecules 6 having the PG depicted in Scheme 2. As a result, the reaction showed reasonably high PG compati- bility. Thus, except for the reaction with carboxylic acid 6o and aryl bromide 6p, the cycloaddition reaction proceeded smoothly to produce adduct 4aa in good to quantitative yields. After the workup, styrene (6a), 1,3-diene 6b, methacrylate 6c, phenol 6d, amides 6e and 6f, aldehyde 6g, aryl chloride 6h, epoxide 6i, oxetane 6j, and borate 6k were quantitatively recovered as themselves. The reaction in the presence of acrylate 6l, acrylamide 6m, or isocyanate 6n provided 4aa in good yield but they were not recovered due to their polymerization (6l and 6m) or reaction with water (6n). In the presence of compounds 6o and 6p, the cycloaddition reaction did not proceed. With these results in hand, we pursued synthesis of various polymerizable molecules by the coupling of a series of diynes and their alkyne (or nitrile) counterparts, 1a-e and 2a-m (or 3a-c) (see Supporting Information for their structure). Representative results are illustrated in Figure 1, where the part derived from diyne 1 and the part derived from alkyne 2 (or nitrile 3) are indicated in red and blue, respectively. Thus, the reaction of 1 and 2 with a dipimp/CoCl 2 3 6H 2 O/Zn catalyst in tetrahydrofuran (THF) at ambient temperature gave 2,3-dihydro-1H-indenes 4 having a polymerizable functionality such as an epoxide (4ab), active alkene (4ac, 4ad, 4be, 4af, 4el), oxetane (4ca, 4cg, 4ck, 4el, 4cn), ester (4ab, 4ac, 4ad, 4af, 4ah, 4ai, 4dj, 4di, 4am), alcohol (4be, 4dj, 4am), phenol (4ah), amine (4ai, 4di) and borate (4cn) *Corresponding author. E-mail: okamos10@kanagawa-u.ac.jp.