Ynolates are the triple-bond version of enolates. In contrast to the well-established chemistry of enolates, 1 only scattered examples of the ynolate chemistry have been reported so far. 2-6 The first example was reported in 1975 by Schöllkopf, who succeeded in the generation of lithium phenylethynolate by extrusion of benzonitrile from 5-lithio-3,4-diphenylisoxazole. 2 Since then, various routes to ynolates have been developed by Kowalski, 3 Stang, 4 Julia, 5 and Rathke. 6 Nevertheless, ynolates received only little attention as synthetic reagents because of lack of convenient methods of their generation. The reactions of ethynolates with aldehydes, 2a,b,3a ketones, 2a,b,3a and imines 2c to give the corresponding -lactones or -lactams have been studied. A silylethynolate 6 is quite attractive because a silyl group can be converted into other functional groups in various ways. 7 In this paper a unique access to and the new reactions of the silylethynolate will be described.Our new route to the lithium silylethynolate involves the acyllithium (R-CO-Li) chemistry. Two different approaches have been developed to utilize the highly reactive intermediate RCOLi. The one involves in situ intermolecular trapping of the acyllithium as studied by Seyferth 8 and others. 9 The other developed by us involves intramolecular conversion of the unstable acyllithium to a more stable but still useful intermediate such as enolate. 10 Now we have studied the reaction of a lithiated silyldiazomethane 1 with carbon monoxide expecting that the extrusion of dinitrogen from an acyllithium 2 should provide the driving force for a clean reaction. This is the case. The results not only provide a unique entry to a lithium ynolate having a silyl group 6 4 (Scheme 1) but also lead to a unique synthetic operation that enables "ketenylation". 11 To a THF-hexane solution of trimethylsilyldiazomethane 12 was added a hexane solution of BuLi (1.2 equiv) at -78°C and the mixture was stirred at that same temperature for 1 h. Then, the mixture was exposed to an atmospheric pressure of carbon monoxide at -78°C for 2 h. Addition of 1.

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Mononuclear cordinatively unsaturated iron(II) complexes having a triazacyclononane ligand were developed as highly efficient and environmentally friendly catalysts for the atom-transfer radical polymerization (ATRP). These iron catalysts showed high performance in the well-controlled ATRP of styrene, methacrylates, and acrylates. The high reactivity of these catalysts led to well-controlled polymerization and block copolymerization even with lower catalyst concentrations.Keywords: atom transfer radical polymerization; environmentally friendly catalyst; iron; ligand design; polymerization Transition metal-catalyzed atom-transfer radical polymerization (ATRP) is a representative example of controlled radical polymerization (CRP), which is an important methodology to construct well-defined polymers on both laboratory and industrial scales. [1,2] In ideal cases, good catalysts for ATRP realize: 1) access to polymers with the desired molecular weight and narrow molecular weight distribution, 2) high reaction rate and durability to achieve complete monomer conversion in the construction of block co-polymers, 3) versatile applicability to several monomers, and 4) minimum residual heavy metal catalysts in the product. While the first three points are general requirements for CRP, the fourth point is a special problem for transition metal-catalyzed reactions. It is known that residual metals make the properties of the formed polymers worse and can be potentially harmful. Facile removal of the catalyst from the polymer has thus been investigated using biphasic systems, solid-supported catalysts, and solubility control of catalysts. [3][4][5][6][7][8] Recent results by Matyjaszewski and coworkers showed that reduction of the catalyst concentration to be a solution for this problem as well. [9]

Environmentally friendly iron(II) catalysts for atom-transfer radical polymerization (ATRP) were synthesized by careful selection of the nitrogen substituents of N,N,N-trialkylated-1,4,9-triazacyclononane (R3 TACN) ligands. Two types of structures were confirmed by crystallography: "[(R3 TACN)FeX2 ]" complexes with relatively small R groups have ionic and dinuclear structures including a [(R3 TACN)Fe(μ-X)3 Fe(R3 TACN)](+) moiety, whereas those with more bulky R groups are neutral and mononuclear. The twelve [(R3 TACN)FeX2 ]n complexes that were synthesized were subjected to bulk ATRP of styrene, methyl methacrylate (MMA), and butyl acrylate (BA). Among the iron complexes examined, [{(cyclopentyl)3 TACN}FeBr2 ] (4 b) was the best catalyst for the well-controlled ATRP of all three monomers. This species allowed easy catalyst separation and recycling, a lowering of the catalyst concentration needed for the reaction, and the absence of additional reducing reagents. The lowest catalyst loading was accomplished in the ATRP of MMA with 4 b (59 ppm of Fe based on the charged monomer). Catalyst recycling in ATRP with low catalyst loadings was also successful. The ATRP of styrene with 4 b (117 ppm Fe atom) was followed by precipitation from methanol to give polystyrene that contained residual iron below the calculated detection limit (0.28 ppm). Mechanisms that involve equilibria between the multinuclear and mononuclear species were also examined.

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