Acrylic acid configuration

The Diels-Alder reaction of a diene with a substituted olefinic dienophile, e.g. 2, 4, 8, or 12, can go through two geometrically different transition states. With a diene that bears a substituent as a stereochemical marker (any substituent other than hydrogen deuterium will suffice ) at C-1 (e.g. 11a) or substituents at C-1 and C-4 (e.g. 5, 6, 7), the two different transition states lead to diastereomeric products, which differ in the relative configuration at the stereogenic centers connected by the newly formed cr-bonds. The respective transition state as well as the resulting product is termed with the prefix endo or exo. For example, when cyclopentadiene 5 is treated with acrylic acid 15, the cw fo-product 16 and the exo-product 17 can be formed. Formation of the cw fo-product 16 is kinetically favored by secondary orbital interactions (endo rule or Alder rule) Under kinetically controlled conditions it is the major product, and the thermodynamically more stable cxo-product 17 is formed in minor amounts only. 

Arenediazonium o-benzenesulfonamide 89 was found to be a new and efficient reagent for the Heck-type arylation reactions of some common substrates containing C-C multiple bonds, i.e., ethyl acrylate, acrylic acid, acroleine, styrene, and cyclopentene <2006T3146>. The reactions are carried out in the presence of Pd(OAc)2 and afford arylated products, for example ethyl cinnamates, cinnamic acids, cinnamic aldehydes, and stilbenes, possessing an ( -configuration, and 1-arylcyclopentenes, in good to excellent yields (Equation 27). 

A haloalkene that contains a stereogenic C=C double bond can usually be coupled with alkenes via the Heck reaction without isomerization. This is illustrated with the three reaction pairs in Figure 16.36. As can be seen, both the as- and the /raw-configured iodoalkenes react with acrolein or methyl vinyl ketone or acrylic acid methyl ester with complete retention of the C=C double bond configuration. These coupling reactions are thus stereoselective and— when considered as a pair—stereospecific. 

The enantioselective hydrogenation of a-(acylamino)acrylic acids (Figure 14.67) is mainly used for the preparation of R- (unnatural) and -configured (natural) amino acids. Such enantiomerically pure amino acids are needed, among others, for the synthesis of peptide-based antibiotics and peptide mimetics. 

Another example from an important group of reactions is that of the polymerization of vinyl derivatives R—CH ==CH2, e.g., styrene, acrylic acid esters etc. The configurations are ... 

It has been attempted to perform template polymer syntheses without using biological sources. Concepts focus on the formation of a complex between monomer molecules and a present macromolecule [4,480], This way the monomer will get preorganized and the polymerization is supposed to follow a zip mechanism controlled by the length and the configuration of the template polymer, offering replication of the molecular weight and control of the stereo structure. Polymerization of acrylic acid in the presence of poly(ethyleneimine), N-vinylimidazole/ poly(methacrylic acid) or acrylonitrile with poly(vinylacetate) have been described [469,470,471,472,473]. Recently the preparation of solid polyelectrolyte complexes from chitosan and sodium-styrenesulfonate has been reported [481]. 

The fust use of an asymmetric Diels-Alder reaction in enantioselective synthesis, reported by Corey and Ensley (1975), involved both diene and dienophile face differentiations (Scheme 74). Addition of 5-(methoxymethyl)cyclopentadiene (304) to acrylic acid (305a) proceeded endo selectively and anti with respect to the diene substituent. Consequently, the relative configuration of the four new chiral centers in (30fo) was determined and, of four possible diastereoisomers, one was formed selectively. As expected, the diene added at the same rate to the two enantiotopic dienophile ir-faces, affording a 1 1 mixture of the enantiomers (lf )-(306a) and (15)-(306a). 

Hydrogenation of acrylic acid esters with high enantioselectivity has usually been accomplished with difficulty. The enantioselective reduction of a,p-unsaturated carboxylates with sodium borohydride in the presence of cobalt-semicorrin complexes has been achieved in up to 96% ee (equation 14). The (Eland (Z)-isomers each afford products of opposite configuration, and the isolated double bonds remain un-touched. ... 

Schubert, G., Schbnecker, B.. Wunderwald, M.. and Ponsold, K.. Synthesis of 17P-configurated acrylic acid derivatives of 19-nor steroids, Pharmazie. 41, 469, 1986. 

Figure 2, Schematic representation of stretched configuration of potassium salt of poly acrylic acid) dissolved...

With the increased level of understanding of the cyclization dynamics as monitored by intramolecular excimer fluorescence, it is now possible to extend this probe to the study of systems more complex than dilute solutions. One such situation involves the structure and dynamics of macromolecular complexes formed between polymeric proton donors and acceptors in aqueous solution. For example, there has been widespread interest in the complexes formed between poly(ethylene glycol) and poly(acrylic acid) or poly(methacrylic acid) in aqueous solution (34, 35). A second, complicated morphological problem is to describe the configurational behavior of polymer chains adsorbed on colloidal particles. This research has relevance to the understanding of steric stabilization. One system of particular interest is the interaction of poly(ethylene glycol) and colloidal silica (36-40). 

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