Methylcinnamic ester

The 1-t-butylphospholane sulfide intermediate to TangPhos was also used to prepare the P,N ligands 48 by reacting the lithium complex with C02 and then oxazoline formation with a range of chiral amino alcohols [69b, 74]. The Ir complexes of these ligands have been successfully used in the reduction of / -methylcinnamic esters (80-99% ee) and methylstilbene derivatives (75-95% ee), a particularly challenging class of unfunctionalized olefins [4 c]. 

The cyclopropane ester was prepared by the reaction between 16 g (t)-butyl 2,5-dimethoxy-4-methylcinnamate and dimethylsulfoxonium methylide, prepared as described in the Kaiser reference in the acknowledgements. Hydrolysis of this ester gave 53% trans-2-(2,5-dimethoxy-4-methylphenyl)cyclopropanecarboxylic acid which, after recrystallization from a MeOH/... 

In addition to this we have several examples of which the polymer conformation of the polymeric complex leads the asymmetrical selectivity Hydrogenation reactions of 1-methylcinnamic acid and 1-acetamidocinnamic acid by several poly(L-amino acid)-Pd complexes are observed (142-144). Poly(L-valine) (/3-form) and poly(/3-benzyl-L-aspartate) (a-helix, sinistral) give dextrorotative products, and poly(L-leucine) and poly( 3-benzyl-L-aspartate) (a-helix, dextral) do levo-rotatory products. Also, optical active poly-/3-hydroxyl esters-Raney Ni catalyst (145) and Ion-exchange resin modified by optical active amino acid-metal complex (146,147) are observed in asymmetrically selective hydrogenations. 

Mild conditions should be employed in alkaline hydrolysis of olefinic esters. Double bonds in many acids migrate readily during saponification. Aqueous alcoholic sodium hydroxide is used in the preparations of 3-ethyl-3-pentenoic acid (56%) and /S-methylcinnamic acid (41%). ... 

The Heck reaction can also be used to prepare pharmaceutical intermediates for NSAID, e. g. suiindac and dehydronabumetone, from bromoaromatic precursors and commercially available alkenes. The central intermediate in the synthesis of suiindac, as developed by Merck [27], is p-fluoro-a-methylcinnamic acid ester condensation of p-fluorobenzaldehyde with propionic anhydride gives p-fluoro-a-methylcinnamic acid. The starting aldehyde is relatively expensive and unstable, and the yield of the Knoevenagel transformation is fairly low (Scheme 5). 

Variation of reactant structure was investigated in order to probe the interaction between NADPME and cinchonine (Figure 4). In a series of cinchonine-modified hydrogenations conducted under standard conditions, Z-a-methylcinnamic acid methyl ester (II) gave... 

The dielectric properties have been studied, especially by W. Kast, who was able to show that the dielectric constant of these substances changes abruptly at the transition points. Fig. 68 shows this effect in the case of the diethyl ester of ethoxybenzal amino-a-methylcinnamic acid. 

It is relevant that the microwave spectrum of o-fluorotoluene leads to a value of 2.72 kJ mol" for the 3-fold barrier. Another recent determination is that by n.m.r. spectroscopy of a barrier of 5 kJ mol" for methyl rotation in u-chlorotoluene dissolved in the nematic phase of 4-amino-4-methoxybenzylidene-a-methylcinnamic acid n-propyl ester. The position of minimal energy was inferred to be that in which the chlorine is staggered to the methyl group. This conclusion has also been reached from semi-empirical MO calculations by the extended Hiickel theory, which give a barrier height of 7.41 kJ mol. ... 

---