Metathesis synthesis

Buchmeiser, M.R., Schuler, N., Schottenberger, H., Kohl, I., Hallbrucker, A. and Wurst, K. (2000) Ferrocenyl- and Octamethylferrocenyl-substituted Phenylene-vinylene-, Thienylenevinylene- and 1,1 -Ferrocenylenevinylene Spaced Ethynes Synthesis, Metathesis Polymerization and Polymer Properties, Designed Monomers Polymers, in press. 

A number of other tetraarylbismuth compounds Ar4BiY, where Y is a group, such as NO , C10 4, OCN , N , etc, have been prepared from the chloride by metathesis. Two tetraalkylbismuth compounds have been reportedly prepared by means of the following synthesis (164) ... 

Synthesis of Heteronuclear and Polynuclear Metal Carbonyls. Heteronuclear metal carbonyls are usually synthesized either by metathesis (27) or addition (28,40). 

Poly(dicyclopentadiene). The development of polydicyclopentadiene [25038-78-2] for reaction injection molding is an area which has generated much interest. The polyDCPD is obtained via metathesis polymerization of high purity (usually greater than 98%) DCPD. Excellent reviews (61—62) of the chemistry and properties of polyDCPD have been pubHshed. The patent Hterature of polyDCPD synthesis, catalysts, modifiers, and appHcations is dominated by Hercules (44 patents) and B. F. Goodrich (43 patents) in the U.S. Other participants are Orkem, SheU, Nippon Zeon, and Teijin. 

A drawback to the Durham method for the synthesis of polyacetylene is the necessity of elimination of a relatively large molecule during conversion. This can be overcome by the inclusion of strained rings into the precursor polymer stmcture. This technique was developed in the investigation of the ring-opening metathesis polymerization (ROMP) of benzvalene as shown in equation 3 (31). 

Alkanes, dipurin-8-yl-synthesis, 5, 574 Alkanes, poly-N-pyrazoIyl-synthesis, 5, 320 Alkanoic acids, tetrazolyl-anti-inflammatory activity, 5, 835 Alkanoic acids, 4-thienyi-cyclization, 4, 905-906 Alkene metathesis mechanism, 1, 668 Alkenes activated... 

Alkene metathesis for the synthesis of carbo- and heterocyclic compounds 97YGK1101. 

Synthesis of heterocycles, among them macroheterocycles, using olefin metathesis 98T4413. 

Synthesis of heterocycles via ring-closing heterodiene metathesis 98JCS(P1)371. 

Synthesis of azasugars and alkaloids via ring-closing metathesis 99EJ0959. 

The introduction of the more hydrolysis-stable tetrafluoroborate [2] and hexaflu-orophosphate systems [3], and especially the development of their synthesis by means of metathesis from alkali salts [4], can be regarded as a first key step towards commercial ionic liquid production. 

A potential drawback of all the routes discussed thus far is that there is little control over polydispersity and molecular weight of the resultant polymer. Ringopening metathesis polymerization (ROMP) is a living polymerization method and, in theory, affords materials with low polydispersities and predictable molecular weights. This methodology has been applied to the synthesis of polyacctylcne by Feast [23], and has recently been exploited in the synthesis of PPV. Bicyclic monomer 12 [24] and cyclophane 13 [25) afford well-defined precursor polymers which may be converted into PPV 1 by thermal elimination as described in Scheme 1-4. 

Kishi s synthesis 290 ring closing metathesis 302 ring expansion 65, 98... 

The last synthesis uses ethanol as the reducing agent. Soluble Na2OsCl6 has been used to make the less soluble salts of other alkali metals by metathesis. 

Fiirstner A (1998) Alkene metathesis in organic synthesis (Topics in organometallic chemistry I). Springer, Berlin Heidelberg New York... 

Olefin Metathesis Directed to Organic Synthesis Principles and Applications... 

Abstract For many years after its discovery, olefin metathesis was hardly used as a synthetic tool. This situation changed when well-defined and stable carbene complexes of molybdenum and ruthenium were discovered as efficient precatalysts in the early 1990s. In particular, the high activity and selectivity in ring-closure reactions stimulated further research in this area and led to numerous applications in organic synthesis. Today, olefin metathesis is one of the... 

Although olefin metathesis had soon after its discovery attracted considerable interest in industrial chemistry, polymer chemistry and, due to the fact that transition metal carbene species are involved, organometallic chemistry, the reaction was hardly used in organic synthesis for many years. This situation changed when the first structurally defined and stable carbene complexes with high activity in olefin metathesis reactions were described in the late 1980s and early 1990s. A selection of precatalysts discovered in this period and representative applications are summarized in Table 1. 

We will focus on the development of ruthenium-based metathesis precatalysts with enhanced activity and applications to the metathesis of alkenes with nonstandard electronic properties. In the class of molybdenum complexes [7a,g,h] recent research was mainly directed to the development of homochi-ral precatalysts for enantioselective olefin metathesis. This aspect has recently been covered by Schrock and Hoveyda in a short review and will not be discussed here [8h]. In addition, several important special topics have recently been addressed by excellent reviews, e.g., the synthesis of medium-sized rings by RCM [8a], applications of olefin metathesis to carbohydrate chemistry [8b], cross metathesis [8c,d],enyne metathesis [8e,f], ring-rearrangement metathesis [8g], enantioselective metathesis [8h], and applications of metathesis in polymer chemistry (ADMET,ROMP) [8i,j]. Application of olefin metathesis to the total synthesis of complex natural products is covered in the contribution by Mulzer et al. in this volume. 

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