Carbon nucleophiles acrylic acid derivatives

Attack on Unsaturated Carbon.- Tervalent phosphorus compounds are effective catalysts for the polymerization of acrylic acid derivatives, and the monomeric adducts which initiate the polymerization usually cannot be isolated. However, by addition of ethyl 2-cyanoacrylate to strongly nucleophilic tervalent phosphorus compounds it was possible to isolate monomeric adducts,... 

Alkenes conjugated with carbonyl groups, such as acrylates (derivatives of acrylic acid), are easily polymerized by a variety of mechanisms. Indeed, these compounds are often difficult to store because they polymerize spontaneously when traces of weak nucleophiles (even water) or radicals (even oxygen) are present. Radical polymerization occurs very easily because the intermediate carbon radical is stabilized by conjugation with the carbonyl group. 

As highly nucleophilic species, pyrrole-2-catbodithioate-anions 772, generated in situ from pyrrole and carbon disulfide in the KOH/DMSO system, add smoothly to electrophilic alkenes like acrylonitrile, acrylamide or methyl acrylate to afford the corresponding derivatives of propionic acid 773 in a yield of up to 62% (Scheme 151) <1999ZOR1534, 2001S0293>. 

Since thiols and thiyl radicals are known to readily undergo addition reactions at unsaturated carbon centers (199, 202, 204), a possible mechanism for this inactivation reaction is shown in Scheme 43. Addition of the active site nucleophilic or radical species followed by protonation or electron transfer, respectively, would yield the thioacrylate derivative and inactive enzyme. Of course, addition to C-2 of propargylic acid is also possible, forming a 2-substituted acrylate derivative instead. 

The NP+C approach (Fig. 4) is undoubtedly the predominant strategy for the preparation of the main pseudodipeptidic unit. This approach usually involves the mild reaction of phosphorus nucleophiles (2 or 3) derived in situ from amino-protected aminophosphinic acids with carbon electrophiles such as acrylic... 

In the late nineteenth century, Michael found that the enolate anion (46) derived from diethyl malonate reacts with ethyl acrylate at the P-carbon (as shown in the illustration) to give an enolate anion, 47, as the product. Remember from Chapter 22 (Section 22.7.4) that the a-proton of a 1,3-dicarbonyl compound such as diethyl malonate is rather acidic (pK of about 11), and even a relatively weak base will deprotonate to form the enolate anion. Michael addition of 46 with ethyl acrylate will give enolate anion 47, and aqueous acid workup leads to the isolated product, 48. Attack at the -carbon is possible because that carbon is less hindered than the acyl carbon, so reaction at the C=C unit is somewhat faster than attack at the acyl carbon. Michael addition occurs with relatively stable carbanion nucleophiles, such as malonate derivative 46 and some other common nucleophiles. Other conjugated carbonyl derivatives react similarly. 

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