[en] Recently, another route was reported, where cyclopenta[2,1-b;3,4-b']dithiophen-4-one (2) was reduced according to a Huang-Minlon modification of the Wolff-Kischner procedure (equation 2).4 The reaction condition for the Wolff-Kischner reduction was harsh; treatment of slurry of 2 in ethylene glycol with potassium hydroxide and hydrazin hydrate for 8 h at 180 .deg. C. Due to the slurry nature of the reaction medium and harsh conditions, the reported yield (65%) has not proved reproducible, instead fluctuating in lower values. Furthermore, synthesis of 2 is not straightforward, hampering a large scale synthesis, although some steps have been improved (equation 2). Cyclopentacetaldehyde (CDT) is a key building block for the construction of a low band gap conjugated polymers, which has recently attracted much attention as a base material for heterojunction solar cells.1 Zirconium and titanium complexes of cyclopentadienyl fused with a thiophene unit are also relevant in the development of a homogenous Ziegler catalyst. The first synthesis of CDT was reported four decades ago (equation 1). The synthetic route was rather lengthy and required use of hazardous chemicals such as lithium aluminum hydride and Br₂. Furthermore, the overall yield and atom economy for equation 1 were very low (theoretical atom economy, 8.0%; practical atom economy, 1.2%, overall yield, 15%), hampering a large scale synthesis of CDT by this route

[en] We developed a shortened synthetic route for a highly active catalyst for CO₂/PO copolymerization. This route allows the scaleable synthesis of the potential catalyst, which will encourage the commercialization of these CO₂/PO copolymers. The carbon dioxide/propylene oxide (CO₂/PO) copolymer is attractive in many aspects and so has attracted much interest. The copolymer, which consists of alternating CO₂ and PO subunits, has 44% by weight CO₂. The CO₂ gas is abundant and cheap, making the copolymer economical to prepare. The copolymer burns gently in air without emission of toxic materials, decomposes at a relatively low temperature of approximately 250 .deg. C without an ash residue, and adheres strongly to a cellulosic substrate. These merits have been blunted by the lack of commercial quantities of the polymer due to the absence of a satisfactory catalytic system. We recently reported a highly active catalyst that has the potential to be applied in a commercial process. A key to the catalyst is the binding of two components-Salen-cobalt(III) unit and quaternary ammonium salt-in proximity regardless of either low catalyst concentration or high polymerization temperature, which consequently allows a high turnover number (TON) and a high molecular weight (M_n) of the resulting polymer

[en] Cyclopentadiene compounds, 2-[CR'R(OMe)]-1,3-Me_2C_5H_3 (R, R' = 2,2'-biphenyl, 2) and 2-[CR'R(OSiMe_3)]- 1,3-Me_2C_5H+3 (R, R' = 2,2'-biphenyl, 3: R = ph, R' = ph, 4: R = 2-naphthyl, R' = H, 5) are readily synthesized from 2-bromo-3-methoxy-1,3-dimethylcyclopentene (1). Reaction of the cyclopentadienes with Ti(NMe_2)_4 in toluene results in clean formation of the cyclopentadienyl tris(dimethylamido)titanium complexes, which are transformed to the trichloride complexes, 2-[CR'R(OMe)]-1,3-Me_2C_5H_2}TiCl_3 (R, R' = 2,2'-biphenyl, 6) and {2-[CR'R(OSiMe_3)]-1,3-Me_2C_5H_2}TiCl_3 (R, R' = 2,2'-biphenyl, 7: R = ph, R' = ph, 8: R = 2-naphthyl, R' = H, 9). Attempts to form C1-bridged Cp/oxido complexes by elimination of MeCl or Me_3SiCl were not successful. X-ray structures of 6, 7 and an intermediate complex {2-[Ph_2C(OSiMe_3)]-1,3-Me_2C_5H_2}TiCl_2(NMe_2) (10) were determined