Organometallic vinylation

Scheme 9 demonstrates the further synthetic application of the thus obtained N,0-acetals. Substitution of the alkoxy or acyloxy group by nucleophiles like enol ethers, enol esters, enamines, other electron-rich olefins, CH-acidic compounds, electron-rich aromatics, isocyanides, trimethylsilyl cyanide, organometallics, vinyl and allyl silanes, hydroxy functions, or trialkylphosphites either catalyzed by Lewis acids or proton acids leads to the product of the amidoalkylation reaction (path a). In the presence of stereocenters as control elements, diasteroselective amidoalkylation reactions can be performed as shown in a large number of examples. On the other side, as Nyberg showed for the first time [196], elimination with formation of enecarbamates [208] and enamides [196,208,209] followed by reaction with electrophiles or nucleophiles (path b) also is possible. 

Use Synthesis of quaternary ammonium compounds, organometallics, vinyl stabilizers. 

The radical polymerization of various other organometallic vinyl monomers has been well studied. For example, in 1978, it was shown that vinylcymantrene 43 undergoes radical homopolymerization in the presence of AIBN as initiator at 50-80 °C in organic solvents such as benzene to yield poly(vinylcymantrene) 44 (Equation (15)). Molecular weights varied from = S x 10 to 3.6 x 10 with broad PDI values in the range 3.2-8.9. 

The attachment of cymantrene groups to polymers has attracted interest for other reasons. Studies have shown, for example, that adherent, abrasion-resistant coatings are formed on metals when thin films of the Mn-containing polymer are subjected to irradiation with UV light. The polymerization of styrene tricarbonylchromium 47 has also been studied.This species is available from the reaction of styrene with Cr(CO)3(NH3)3. Although the Cr monomer 47 resisted attempts at homopolymerization, co-polymerizations with styrene, methyl acrylate, as well as with 41 to yield bimetallic polymers 48 were possible (Equation (17)). In addition, co-polymerization with vinyl-ferrocene afforded co-polymers of low molecular weight (Mn = ca. 4,000). A variety of other organometallic vinyl momomers 49 has been successfully polymerized to yield polymers 50 that contain pendant Gr, W, and Ir carbonyl moieties (Equation (18)). ... 

Coupling of Vinyl Phosphonates and Triflates to Organometallic Reagents - vinyl phosphates review Synthesis 1992, 333,... 

The insertion of calcium atoms into vinyl and aryl carbon-fluorine bonds has been reported Only the resulting organometallic from the aryl derivatives appears to live long enough to be trapped by water [J]... 

Two types of organometallic photoinitiators for free radical vinyl polymerization are considered (1) transi-... 

It is clear from the preceding discussion that organometallic photoinitiators (metal carbonyl or chelate derivatives) can provide a convenient route for synthesizing vinyl polymers with a variety of different reactive end group or photoreactive pendant groups or side chains through the polymer chain. 

In more recent years two new types of antifouling composition have been developed, using organometallic compounds as poisons. In one type, based chiefly on vinyl resin and organotin compounds (e.g. tributyltin fluoride), the poison and resin form a solid solution. As the poison dissolves from the surface of the film, more poison diffuses from deeper in the film to... 

This organometallic coupling reaction is useful in organic synthesis because it forms carbon-carbon bonds, thereby making possible the preparation of larger molecules from smaller ones. As the following examples indicate, the coupling reaction can be carried out on aryl and vinylic halides as well as on alkyl halides. 

As shown by Marvell and Whalley in 1970,5 divinylcyclohexa-nols, resulting from the reaction of a vinyl organometallic reagent... 

Metalated epoxides can react with organometallics to give olefins after elimination of dimetal oxide, a process often referred to as reductive alkylation (Path B, Scheme 5.2). Crandall and Lin first described this reaction in their seminal paper in 1967 treatment of tert-butyloxirane 106 with 3 equiv. of tert-butyllithium, for example, gave trans-di-tert-butylethylene 110 in 64% yield (Scheme 5.23), Stating that this reaction should have some synthetic potential , [36] they proposed a reaction pathway in which tert-butyllithium reacted with a-lithiooxycarbene 108 to generate dianion 109 and thence olefin 110 upon elimination of dilithium oxide. The epoxide has, in effect, acted as a vinyl cation equivalent. 

A second powerful route to functionalized allylboron compounds involves the reaction of an a-haloalkylboronatc and a vinyl organometallic reagent3 4-28-29, 50c-92 04. This method is especially useful for the preparation of allylboron compounds not accessible via the allylorganometal-lic route. Notable examples that fall into this category are ( )-4,4,5,5-tctramethyl-2-[4-(tetrahy-dro-2//-pyran-2-yloxy)-2-butenyl]-l,3,2-dioxaborolane (yield 41 %, 93% E) and (E)- or (Z)-2-(l,l-dimethyl-2-butenyl)-4,4,5,5-tetramethyl-1.3,2-dioxaborolane (yield 77-84%. 98% E or 93% Z). 

G. H. Posner, Addition of Organometallic Reagents to Chiral Vinyl Sulfoxides in Asymmetric Synthesis. J. D. Morrison, Ed. Vol. 2, p. 225, Academic, New York 1983. 

Vinyl sulfones, being good Michael acceptors, have been regarded as useful reagents for carbon-carbon bond formation. Nucleophiles used often are organometallic reagents, enamines and enolate anions and the Michael addition products are usually obtained in... 

TABLE 6. Conjugate addition of organometallic reagents to vinyl sulfones55... 

Deprotonation of the vinylic proton is a serious side-reaction in the conjugate addition of organometallic reagents to y-siloxy-a, /J-unsaturated sulfones (89)63b. The use of the... 

The work on vinyl sulphones and their reactions with Grignard reagents, in the presence of transition metal catalysts, all emanates from Julia s laboratory191-195, with the exception of a note196 that presents evidence for SET processes in the alkylation of vinyl sulphones by organometallic reagents. 

F. Desulfonylation of Acetylenic and Vinylic Sulfones by Organometallic Reagents... 

Three possible mechanisms may be envisioned for this reaction. The first two i.e. 1) Michael addition of R M to the acetylenic sulfone followed by a-elimination of LiOjSPh to yield a vinyl carbene which undergoes a 1,2 aryl shift and 2) carbometallation of the acetylenic sulfone by R M followed by a straightforward -elimination, where discarded by the authors. The third mechanism in which the organometallic reagent acts as an electron donor and the central intermediates is the radical anion ... 

For a list of organometallic reagents that react with vinylic epoxides, with references, see Ref. 568, p. 123. 

Another publication is the Index of Reviews in Organic Chemistry , complied by Lewis, Chemical Society, London, a classified listing of review articles. The first volume, published in 1971, lists reviews from 1960 (in some cases much earlier) to 1970 in alphabetical order of topic. Thus four reviews are listed under Knoevenagel condensation , five under Inclusion compounds , and one under Vinyl ketones. There is no index. A second volume (1977) covers the literature to 1976. Annual or biannual supplements appeared from 1979 until the publication was terminated in 1985. Classified lists of review articles on organometallic chemistry are found in articles by Smith and Walton and by Bruce.A similar list for heterocyclic chemistry is found in articles by Katritzky and others.See also the discussion of the Index of Scientific Reviews, page 1638. 

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